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Question
A person walks across a room in barefeet and puts his foot on a drawing pin lying on the floor. He lets out a cry. Explain what happens in his nervous system in bringing about this response.
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Solution
It is an example of a reflex action. The stimulus in this example is pain which is felt by the foot on touching the drawing pin. This pain is sensed by a receptor in the foot. The receptor triggers an impulse to a sensory neuron which transmits the message to the spinal cord. Here, the impulse is passed on to a relay neuron which, in turn, passes it to a motor neuron. The motor neuron passes the impulse to a muscle in the foot. The muscle, then, contracts and pulls the foot away from the drawing pin.
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