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ICSE Class 8 Biology Question 2 of 10

Nervous System in Humans — Question 4

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Question 4

What is reflex action? Explain the reflex arc with the help of an example.

Answer

An automatic, spontaneous and mechanical response to a stimulus controlled by the spinal cord without the involvement of the brain is called a reflex action.

The path that an impulse takes in a reflex action is called a reflex arc. The reflex arc involves three neurons — sensory neurons, association neurons and motor neurons.

  • If we touch a hot object, a stimulus triggers an impulse in a receptor on the skin.
  • The impulse then travels from the receptor through a sensory neuron to the spinal cord.
  • In the spinal cord, it passes through an association neuron to a motor neuron and finally reaches the muscles.
  • The muscles of the effector organ contract moving it away from the hot object.

Below flow chart shows a simple reflex action of immediate withdrawal of hand on touching a hot object:

What is reflex action? Explain the reflex arc with the help of an example. Nervous System in Humans, Living Science Biology Ratna Sagar Solutions ICSE Class 8.