Question

The diagram given below is a representation of a certain phenomenon pertaining to the nervous system. Study the diagram and answer the following questions:

(i) Name the phenomenon which is being depicted.
(ii) Give the technical term for the point of contact between the two nerve cells.
(iii) Name the parts 1, 2, 3, and 4.
(iv) Write the functions of parts 5 and 6
(v) How does the arrangement of neurons in the spinal cord differ from that of the brain?

Answer 1

(i) Path of reflex action or reflex arc

(ii) Synapse

(iii)

1 – Receptor
2 – Dorsal root ganglion
3 – White matter
4 – Grey matter

(iv)

Function of part 5 (Association neuron) – Relays information from the sensory neuron to the motor neuron.
Function of part 6 (Spinal nerve) – A response impulse is sent to the effector through the spinal nerve.

(v) In the brain, the cell bodies of neurons lie in the cortex, i.e. the outer region (grey matter) and axons lie on in the inner region (white matter). In the spinal cord, the cell bodies lie in the medullary region (inner grey matter) and axons lie on the outer side, i.e. cortex (outer white matter).