Question 1:
Diagram below shows a cross-section of part of the nervous system.


(a)(i) Name structure P.

(a)(ii) State the function of P.

(b)(i) Why is Q swollen at the dorsal root?

(b)(ii) Complete the Diagram with the neurones involved in a reflex action. Mark the direction of the impulse movement on the neurones.



(c) Compare two structures of a sensory neurone and a motor neurone.

(d) If the spinal nerve is cut off at R, what is the effect on the organ which is connected to it?
Explain your answer.

(e) Azmin’s finger accidentally touches a flame.
Explain briefly how his reflex action functions to avoid the injury.


Answer:
(a)(i)
P : Spinal cord

(a)(ii)
Function of P : Controls reflex actions.

(b)(i)
To place the cell bodies of the afferent neurones.

(b)(ii)



(c)


(d)
The organ is unable to respond. Impulses cannot flow to the effector.

(e)
- The receptor detects heat and triggers an impulse.
- The impulse is sent to the spinal cord through the afferent neurone.
- The impulse flows through the afferent neurone which synapses with the interneurone and then synapses with the efferent neurone.
- The efferent neurone sends an impulse to the effector.
- The hand is pulled away from flame.