The human body contains a large number of cells A which are very long and branched, and look like electric wires. The longest branch of this cell is B whereas there are many small branches C. Any two A cells do not join to one another completely in the human body. There is a microscopic gap D between every pair of adjacent A cells through which electric impulses can pass by the release of a chemical substance.

(a) What are cells A ?

(b) What is the name of (i) branch B, and (ii) branches C ?

(c) What is the microscopic gap D is known as ?

(d) What is the function of cells like A in the human body ?

(e) The cells A are of three types. Name the three types.

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Solution

(a) Cella A are Neurons. . Neurons are the largest cells in the human body, which look like electric wires.
(b) (i) Name of branch B- Axon

(ii) Name of branch C - Dendrites

(c) The microscopic gap D is known as Synaptic Cleft or simply Synapse.

(d) Nerve cells help to transmit sensory impulses to the spinal cord and to the brain. They also help to transmit motor impulses from the brain via the spinal cord to the motor nerve which are connected to the muscles to implement the action as instructed and necessary by the brain.

(e) Cell A that is Neurons are of three types

(i) Sensory Neurons

(ii) Motor Neurons

(iii) Relay Neurons

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Similar questions

(a) Why are nerve cells long and have branches ?
(b) What is the other name of a nerve cell ?

P is a cell (or group of cells) in the human body which is sensitive to a particular type of stimulus and conveys the message to CNS through nerves Q. On the other hand, R is part of the human body which can respond to a stimulus according to the instructions sent from the CNS through nerves S.

(a) What is P ? Name give organs which contain cells (or group of cells ) like P.

(b) Name the nerves Q.

(d) Name nerves S.

(e) How do messages travel through the nerves Q and S ?

Q. State whether the following statements are true or false :
(a) Unicellular organisms have one-celled body.
(b) Muscle cells are branched.
(c) Amoeba has irregular shape.
(d) All the cells in our body are alike.
(e) A hen's egg is a group of cells.
(f) The basic living unit of an organism is organ.

What are the limitations of the nervous system in the human body?
I. The electrical impulses reach only those cells that are connected by the nervous tissue and not each and every cell of the body.
II. Cells cannot continuously create and transmit electrical impulses, once an electrical impulse is generated and transmitted, the cell will take some time to reset its mechanism and create a new electrical impulse.

Q. (a) Why nerve cells are long and have branches?

(b) What regulates the movement of substances into and out of cell?

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