Question: A section of 155th Street connects Harlem River Drive and what Avenue?

Answer: Bradhurst

155th Street starts on the West Side at Riverside Drive, crossing Broadway, Amsterdam Avenue and St. Nicholas Avenue. At St. Nicholas Place, the terrain drops off steeply, and 155th Street is carried on a 1,600-foot (490 m) long viaduct, a City Landmark constructed in 1893, that slopes down towards the Harlem River, continuing onto the Macombs Dam Bridge, crossing over (but not intersecting with) the Harlem River Drive. <hl> A separate, unconnected section of 155th Street runs under the viaduct, connecting Bradhurst Avenue and the Harlem River Drive. <hl>

155th Street starts on the West Side at Riverside Drive, crossing Broadway, Amsterdam Avenue and St. Nicholas Avenue. At St. Nicholas Place, the terrain drops off steeply, and 155th Street is carried on a 1,600-foot (490 m) long viaduct, a City Landmark constructed in 1893, that slopes down towards the Harlem River, continuing onto the Macombs Dam Bridge, crossing over (but not intersecting with) the Harlem River Drive. A separate, unconnected section of 155th Street runs under the viaduct, connecting <hl> Bradhurst <hl> Avenue and the Harlem River Drive.


Question: 181st Street runs through what neighborhood?

181st Street is a major thoroughfare running through the Washington Heights neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. The west end is called Plaza Lafayette.

Answer: Washington Heights

<hl> 181st Street is a major thoroughfare running through the Washington Heights neighborhood. <hl> It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. The west end is called Plaza Lafayette.

181st Street is a major thoroughfare running through the <hl> Washington Heights <hl> neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. The west end is called Plaza Lafayette.


Question: What is the west end of 181st Street called?

Answer: Plaza Lafayette

181st Street is a major thoroughfare running through the Washington Heights neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. <hl> The west end is called Plaza Lafayette . <hl>

181st Street is a major thoroughfare running through the Washington Heights neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. The west end is called <hl> Plaza Lafayette <hl>.

The west end is called <hl> Plaza Lafayette <hl> .


Question: Does Plaza Lafayette refer to the east or west end of 181st Street?

Answer: west

181st Street is a major thoroughfare running through the Washington Heights neighborhood. <hl> It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west , near the George Washington Bridge and the Hudson River. <hl> The west end is called Plaza Lafayette.

181st Street is a major thoroughfare running through the Washington Heights neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the <hl> west <hl>, near the George Washington Bridge and the Hudson River. The west end is called Plaza Lafayette.

It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the <hl> west <hl> , near the George Washington Bridge and the Hudson River.


Question: Which river does 181st Street run near?

Answer: Hudson River

181st Street is a major thoroughfare running through the Washington Heights neighborhood. <hl> It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River . <hl> The west end is called Plaza Lafayette.

181st Street is a major thoroughfare running through the Washington Heights neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the <hl> Hudson River <hl>. The west end is called Plaza Lafayette.

It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the <hl> Hudson River <hl> .


Question: Which road runs from the Washington Bridge to the Henry Hudson Parkway?

Answer: 181st Street

<hl> 181st Street is a major thoroughfare running through the Washington Heights neighborhood. <hl> It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. The west end is called Plaza Lafayette.

<hl> 181st Street <hl> is a major thoroughfare running through the Washington Heights neighborhood. It runs from the Washington Bridge in the east, to the Henry Hudson Parkway in the west, near the George Washington Bridge and the Hudson River. The west end is called Plaza Lafayette.


Question: In which direction is 181st Street largely residential?

West of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.

Answer: West

<hl> West of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. <hl> East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.

<hl> West <hl> of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.


Question: In which direction is 181st Street mostly commercial?

Answer: East

East of Fort Washington Avenue

West of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. <hl> East of Fort Washington Avenue <hl> , the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.

West of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. <hl> East <hl> of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.


Question: Which street marks the western boundary of the shopping distrit?

Answer: Fort Washington Avenue

<hl> West of Fort Washington Avenue , 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. <hl> East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.

West of <hl> Fort Washington Avenue <hl>, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. It is the area's major shopping district.

West of <hl> Fort Washington Avenue <hl> , 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents.


Question: Which river touches the major shopping district near 181st Street?

Answer: Harlem

West of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. <hl> East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the Harlem River. <hl> It is the area's major shopping district.

West of Fort Washington Avenue, 181st Street is largely residential, bordering Hudson Heights and having a few shops to serve the local residents. East of Fort Washington Avenue, the street becomes increasingly commercial, becoming dominated entirely by retail stores where the street reaches Broadway and continues as such until reaching the <hl> Harlem <hl> River. It is the area's major shopping district.


Question: How many subway lines serve 181st Street?

181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.

Answer: two

<hl> 181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). <hl> The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.

181st Street is served by <hl> two <hl> New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.


Question: How many metres apart are 181st Street's two subway stations?

Answer: 500

181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). <hl> The stations are about 500 metres (550 yd) from each other and are not connected. <hl> The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.

181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). The stations are about <hl> 500 <hl> metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.


Question: On what avenue is the George Wasington Bridge Bus Terminal?

Answer: Fort Washington Avenue

<hl> 181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). <hl> The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.

181st Street is served by two New York City Subway lines; there is a 181st Street station at <hl> Fort Washington Avenue <hl> on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.


Question: Which road is the Trans-Manhattan Expressway's last south/west exit?

Answer: 181st Street

<hl> 181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). <hl> The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.

<hl> 181st Street <hl> is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.


Question: 187th Street runs from Laurel Hill Terrace in the east to which avenue in the west?

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley. West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.

Answer: Chittenden Avenue

<hl> 187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. <hl> The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley. West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to <hl> Chittenden Avenue <hl> in the west near the George Washington Bridge and Hudson River. The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley. West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.


Question: What is 187th Street interrupted by?

Answer: stairs

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. <hl> The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley. <hl> West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. The street is interrupted by a long set of <hl> stairs <hl> east of Fort Washington Avenue leading to the Broadway valley. West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.


Question: Where do the stairs interrupting 187th street lead to?

Answer: Broadway valley

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. <hl> The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley . <hl> West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the <hl> Broadway valley <hl>. West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood.

The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the <hl> Broadway valley <hl> .


Question: An area of 187th Street serves as the main shopping district for which neighborhood?

Answer: Hudson Heights

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley. <hl> West of there, it is mostly lined with store fronts and serves as a main shopping district for the Hudson Heights neighborhood. <hl>

187th Street crosses Washington Heights and running from Laurel Hill Terrace in the east to Chittenden Avenue in the west near the George Washington Bridge and Hudson River. The street is interrupted by a long set of stairs east of Fort Washington Avenue leading to the Broadway valley. West of there, it is mostly lined with store fronts and serves as a main shopping district for the <hl> Hudson Heights <hl> neighborhood.


Question: Which is the eastmost intersection that 187th Street has?

187th Street intersects with, from East to West, Laurel Hill Terrace, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue.

Answer: Laurel Hill Terrace

<hl> 187th Street intersects with, from East to West, Laurel Hill Terrace , Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue. <hl>

187th Street intersects with, from East to West, <hl> Laurel Hill Terrace <hl>, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue.

187th Street intersects with, from East to West, <hl> Laurel Hill Terrace <hl> , Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue.


Question: Which is the westernmost intersection that 187th Street has?

Answer: Chittenden Avenue

<hl> 187th Street intersects with, from East to West, Laurel Hill Terrace, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue . <hl>

187th Street intersects with, from East to West, Laurel Hill Terrace, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and <hl> Chittenden Avenue <hl>.

187th Street intersects with, from East to West, Laurel Hill Terrace, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and <hl> Chittenden Avenue <hl> .


Question: Wadsworth Avenue is intersected by what street?

Answer: 187th Street

<hl> 187th Street intersects with, from East to West, Laurel Hill Terrace, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue. <hl>

<hl> 187th Street <hl> intersects with, from East to West, Laurel Hill Terrace, Amsterdam Avenue, Audubon Avenue, St. Nicholas Avenue, Wadsworth Avenue, Broadway, Bennett Avenue, Overlook Terrace, Fort Washington Avenue, Pinehurst Avenue, Cabrini Boulevard and Chittenden Avenue.


Question: Which school is located on Cabrini Boulevard?

The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street

Answer: P.S. 187

The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. <hl> The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street <hl>

The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. The local public elementary school <hl> P.S. 187 <hl> is located on Cabrini Boulevard, just north of the eponymous 187th Street


Question: On what street is the Dombrov Shtiebel?

Answer: 187th Street

<hl> The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. <hl> The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street

The many institutions on <hl> 187th Street <hl> include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street


Question: Which University has a campus on 187th Street?

Answer: Yeshiva University

<hl> The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University . <hl> The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street

The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of <hl> Yeshiva University <hl>. The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street

The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of <hl> Yeshiva University <hl> .


Question: Cabrini Boulevard is just north of what street?

Answer: 187th Street

<hl> The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. <hl> The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street

The many institutions on <hl> 187th Street <hl> include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street


Question: On what street is the Mount Sinai Jewish Center?

Answer: 187th Street

<hl> The many institutions on 187th Street include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. <hl> The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street

The many institutions on <hl> 187th Street <hl> include Mount Sinai Jewish Center, the Dombrov Shtiebel, and the uptown campus of Yeshiva University. The local public elementary school P.S. 187 is located on Cabrini Boulevard, just north of the eponymous 187th Street


Question: What is the center of the nervous system in all creatures?

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

Answer: The brain

<hl> The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. <hl> Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

<hl> The brain <hl> is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.


Question: What is the most complex organ in an animal's body?

Answer: The brain

<hl> The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. <hl> Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

<hl> The brain <hl> is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.


Question: In people, how many neurons make up the cerebral cortex?

Answer: 15–33 billion

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. <hl> In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. <hl> These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain <hl> 15–33 billion <hl> neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.


Question: Neurons in the brain interact with each other by fibers called what?

Answer: axons

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. <hl> These neurons communicate with one another by means of long protoplasmic fibers called axons , which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells. <hl>

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called <hl> axons <hl>, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

These neurons communicate with one another by means of long protoplasmic fibers called <hl> axons <hl> , which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.


Question: A few animals without spines that do not have a brain are what?

Answer: sponges, jellyfish, adult sea squirts

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. <hl> Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. <hl> The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as <hl> sponges, jellyfish, adult sea squirts <hl> and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.


Question: Hormones secreted are driven by what organ in the body?

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.

Answer: The brain

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. <hl> The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. <hl> This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. <hl> The brain <hl> acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.


Question: What type of responsiveness can be used without a brain?

Answer: reflexes

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. <hl> Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain. <hl>

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as <hl> reflexes <hl> can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.


Question: Reflexes only require one of what two structures in a body?

Answer: spinal cord or peripheral ganglia

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. <hl> Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia , but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain. <hl>

Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the <hl> spinal cord or peripheral ganglia <hl>, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.

Some basic types of responsiveness such as reflexes can be mediated by the <hl> spinal cord or peripheral ganglia <hl> , but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.


Question: Which part of a computer does the brain most resemble?

The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from an electronic computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways, analogous to the central processing unit (CPU) in a computer.

Answer: central processing unit (CPU)

The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. <hl> Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from an electronic computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways, analogous to the central processing unit (CPU) in a computer. <hl>

The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from an electronic computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways, analogous to the <hl> central processing unit (CPU) <hl> in a computer.


Question: Animals with a spine are called what?

This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways.

Answer: vertebrates

<hl> This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates . <hl> It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways.

This article compares the properties of brains across the entire range of animal species, with the greatest attention to <hl> vertebrates <hl>. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways.

This article compares the properties of brains across the entire range of animal species, with the greatest attention to <hl> vertebrates <hl> .


Question: Animals without a spine are called what?

The shape and size of the brain varies greatly in different species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates.

Answer: invertebrates

The shape and size of the brain varies greatly in different species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. <hl> Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates . <hl>

The shape and size of the brain varies greatly in different species, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from <hl> invertebrates <hl>.

Some aspects of brain structure are common to almost the entire range of animal species; others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from <hl> invertebrates <hl> .


Question: The easiest way to learn about brain anatomy is by what?

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

Answer: visual inspection

<hl> The simplest way to gain information about brain anatomy is by visual inspection , but many more sophisticated techniques have been developed. <hl> Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

The simplest way to gain information about brain anatomy is by <hl> visual inspection <hl>, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

The simplest way to gain information about brain anatomy is by <hl> visual inspection <hl> , but many more sophisticated techniques have been developed.


Question: Brain tissue is naturally soft, but can be stiffened with what liquid?

Answer: alcohol

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. <hl> Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. <hl> Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in <hl> alcohol <hl> or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.


Question: The two main areas of the brain are what colors?

Answer: grey matter, with a dark color, separated by areas of white matter

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. <hl> Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter , with a lighter color. <hl> Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called <hl> grey matter, with a dark color, separated by areas of white matter <hl>, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

Visually, the interior of the brain consists of areas of so-called <hl> grey matter, with a dark color, separated by areas of white matter <hl> , with a lighter color.


Question: What instrument can you use to examine the microstructure of the brain?

Answer: microscope

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. <hl> It is also possible to examine the microstructure of brain tissue using a microscope , and to trace the pattern of connections from one brain area to another. <hl>

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a <hl> microscope <hl>, and to trace the pattern of connections from one brain area to another.

It is also possible to examine the microstructure of brain tissue using a <hl> microscope <hl> , and to trace the pattern of connections from one brain area to another.


Question: Grey matter of the brain is what color?

Answer: dark color

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. <hl> Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color , separated by areas of white matter, with a lighter color. <hl> Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a <hl> dark color <hl>, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.

Visually, the interior of the brain consists of areas of so-called grey matter, with a <hl> dark color <hl> , separated by areas of white matter, with a lighter color.


Question: Brains of organisms are made up mostly of what two classes of cells?

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

Answer: neurons and glial cells

<hl> The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells . <hl> Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

The brains of all species are composed primarily of two broad classes of cells: <hl> neurons and glial cells <hl>. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

The brains of all species are composed primarily of two broad classes of cells: <hl> neurons and glial cells <hl> .


Question: Glial cells are also referred to as what?

Answer: glia or neuroglia

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. <hl> Glial cells (also known as glia or neuroglia ) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. <hl> Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as <hl> glia or neuroglia <hl>) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

Glial cells (also known as <hl> glia or neuroglia <hl> ) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development.


Question: Which of the two broad classes of cells: neurons and glial cells send signals to other cells?

Answer: neurons

<hl> The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. <hl> Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

The brains of all species are composed primarily of two broad classes of cells: <hl> neurons <hl> and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.


Question: Axons send signals that are named what?

Answer: action potentials

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. <hl> These axons transmit signals in the form of electrochemical pulses called action potentials , which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. <hl> Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called <hl> action potentials <hl>, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

These axons transmit signals in the form of electrochemical pulses called <hl> action potentials <hl> , which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second.


Question: What is the typical speed that axons send their electrical signals?

Answer: 1–100 meters per second

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. <hl> These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second . <hl> Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to specific target cells over long distances. They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell, (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer. These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of <hl> 1–100 meters per second <hl>. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.

These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of <hl> 1–100 meters per second <hl> .


Question: Axons send signals to other neurons by junctions known as what?

Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.

Answer: synapses

<hl> Axons transmit signals to other neurons by means of specialized junctions called synapses . <hl> A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.

Axons transmit signals to other neurons by means of specialized junctions called <hl> synapses <hl>. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.

Axons transmit signals to other neurons by means of specialized junctions called <hl> synapses <hl> .


Question: The neurotansmitter binds to what of a target cell?

Answer: receptor molecules

Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. <hl> The neurotransmitter binds to receptor molecules in the membrane of the target cell. <hl>

Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to <hl> receptor molecules <hl> in the membrane of the target cell.


Question: An axon can connect to how many other cells?

Answer: several thousand

Axons transmit signals to other neurons by means of specialized junctions called synapses. <hl> A single axon may make as many as several thousand synaptic connections with other cells. <hl> When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.

Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as <hl> several thousand <hl> synaptic connections with other cells. When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.


Question: How many synapses does the human brain supposedly contain?

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

Answer: 100 trillion synapses;

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. <hl> The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. <hl> The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately <hl> 100 trillion synapses; <hl> even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.


Question: The fruit fly has a brain that has how many synapses?

Answer: several million

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. <hl> The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million . <hl> The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains <hl> several million <hl>. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains <hl> several million <hl> .


Question: A synapse whose purpose is to excite the target cell are called what?

Answer: excitatory

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. <hl> The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. <hl> A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

Synapses are the key functional elements of the brain. The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are <hl> excitatory <hl> (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.


Question: The primary job of the brain is what?

Answer: cell-to-cell communication

Synapses are the key functional elements of the brain. <hl> The essential function of the brain is cell-to-cell communication , and synapses are the points at which communication occurs. <hl> The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

Synapses are the key functional elements of the brain. The essential function of the brain is <hl> cell-to-cell communication <hl>, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses; even the brain of a fruit fly contains several million. The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways. A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.

The essential function of the brain is <hl> cell-to-cell communication <hl> , and synapses are the points at which communication occurs.


Question: Axons grouped together are known as what?

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Answer: nerve fiber tracts

<hl> Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts . <hl> A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Most of the space in the brain is taken up by axons, which are often bundled together in what are called <hl> nerve fiber tracts <hl>. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Most of the space in the brain is taken up by axons, which are often bundled together in what are called <hl> nerve fiber tracts <hl> .


Question: An axon that can greatly increase speed of signals is wrapped in what?

Answer: sheath of myelin

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. <hl> A myelinated axon is wrapped in a fatty insulating sheath of myelin , which serves to greatly increase the speed of signal propagation. <hl> (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating <hl> sheath of myelin <hl>, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

A myelinated axon is wrapped in a fatty insulating <hl> sheath of myelin <hl> , which serves to greatly increase the speed of signal propagation.


Question: Myelin is what color in the brain?

Answer: white

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). <hl> Myelin is white , making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies. <hl>

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is <hl> white <hl>, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Myelin is <hl> white <hl> , making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.


Question: Most of the space in the brain is made up of what structures?

Answer: axons

<hl> Most of the space in the brain is taken up by axons , which are often bundled together in what are called nerve fiber tracts. <hl> A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Most of the space in the brain is taken up by <hl> axons <hl>, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

Most of the space in the brain is taken up by <hl> axons <hl> , which are often bundled together in what are called nerve fiber tracts.


Question: Grey matter of the brain consist of lots of what?

Answer: neuron cell bodies

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). <hl> Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies . <hl>

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of <hl> neuron cell bodies <hl>.

Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of <hl> neuron cell bodies <hl> .


Question: Creatures that have a diffuse nerve net are called what?

Except for a few primitive organisms such as sponges (which have no nervous system) and cnidarians (which have a nervous system consisting of a diffuse nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body shape (that is, left and right sides that are approximate mirror images of each other). All bilaterians are thought to have descended from a common ancestor that appeared early in the Cambrian period, 485-540 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, including vertebrates, it is the most complex organ in the body. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".

Answer: cnidarians

<hl> Except for a few primitive organisms such as sponges (which have no nervous system) and cnidarians (which have a nervous system consisting of a diffuse nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body shape (that is, left and right sides that are approximate mirror images of each other). <hl> All bilaterians are thought to have descended from a common ancestor that appeared early in the Cambrian period, 485-540 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, including vertebrates, it is the most complex organ in the body. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".

Except for a few primitive organisms such as sponges (which have no nervous system) and <hl> cnidarians <hl> (which have a nervous system consisting of a diffuse nerve net), all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body shape (that is, left and right sides that are approximate mirror images of each other). All bilaterians are thought to have descended from a common ancestor that appeared early in the Cambrian period, 485-540 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body. At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates. The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, including vertebrates, it is the most complex organ in the body. Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".