Question

The diagram given below shows the internal structure of the spinal cord, depicting a simple reflex. Study the same and then answer the questions that follow:

(i) Name the parts numbered 1 to 5.
(ii) Using the letters of the alphabet shown in the figure indicate the direction in which an impulse enters and leaves the spinal cord.
(iii) What is the term given to the point of contact between two nerve cells?
(iv) What is meant by ‘simple reflex’ ? Give two examples of simple reflexes and name the stimuli too.
(v) How does the arrangement of nerve cells in the spinal cord differ from that in the brain?

Answer 1

(i)
1. Sensory or Afferent fiber.
2. The cell body of the sensory neurons.
3. White matter.
4. The cell body of the motor neurons.
5. Spinal nerve.

(ii) BCA

(iii) Synapse.

(iv) Simple reflex: It is an involuntary automatic, quick response to a stimulus.
Examples:
(a) The closing of the eyelids when a strong beam of light is flashed.
(b) The withdrawal of the hand when it is pricked.

(v) In spinal cord white matter is outside and gray matter is inside. In brain white matter is inside and gray matter is outside.