Q1 of 102 Page 118

What is meant by reflex action?

When a receptor is stimulated, it sends a signal to the central nervous system, where the brain co-ordinates the response. But sometimes a very quick response is needed, one that does not need the involvement of the brain. This is a reflex action. Reflex actions are rapid and happen without us thinking.


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6

Explain the following terms:

Gray matter .......................

 7

Rearrange the following in correct sequence pertaining to what is given within brackets at the end.


(a) Effector- Sensory neuron - Receptor- Motor neuron - Stimulus - Central nervous system - Response (Reflex arc)


 


(b) Repolarization - Depolarization - Resting (polarized) (during conduction of nerve impulse through a nerve fiber)


 


(c) Axon endings- Nucleus-Dendrites-Axon - Perikaryon- Dendron (Neuron structure)


 


(d) Diencephalon -Cerebellum - Medulla oblongata - Pons - Cerebrum - midbrain (sequence of parts of the human brain).

 1

State whether the following are simple reflexes, conditioned reflexes or neither of the two.

(i) Sneezing………………


(ii) Blushing ……………………..


(iii) Contraction of eye pupil ..........


(iv) Lifting up a book ..............


(v) Knitting without looking.............


(vi) The sudden application of brakes of' the cycle on sighting an obstacle in front .........................

 2

What are the advantages of having a nervous system?