Q.7 Define reflex action. Explain it with an example
Answer:
REFLEX ACTION
Definition
Sometimes the involuntary response produced by the CNS is very quick. Such a response is called reflex action.
Types of action
When CNS sends impulses to muscles and glands, two types of actions or responses result.
Voluntary Actions
The higher centers of brain control the conscious action or voluntary actions.
Or
The actions which are done by our will are called voluntary actions.
Examples
Picking of book from the table, to take meal three times a day etc.
Involuntary Actions
Definition
When impulses are not passed to the higher centres of brain, it results in responses which are not under conscious control. Such responses are called involuntary actions.
Or
The actions which are not done by our will are called involuntary actions
Examples
Heart beat, blood pressure etc.
Reflex arc
The pathway followed by the nerve impulses for producing a reflex action is called reflex arc.
Example of Reflex Action
The most common example of reflex action is the withdrawal of hand after touching a hot object. . Explanation
In this reflex action, spinal cord acts as coordinator. Heat stimulates temperature and pain receptors in skin. A nerve impulse is generated which is carried by sensory neurons to the interneurons of spinal cord.
From interneurons, the impulse is passed to the motor neurons which carry it to the muscles of the arm. As a result, the muscles contract to withdraw hand. During it, other interneurons transmit nerve impulses up to brain so that the person becomes aware of pain and what happened.
