Question 50: What are reflex actions? Give two examples. Explain a reflex arc.
Answer:
Reflex action is a rapid or quick response to stimulus (involuntary mechanism) because of lower number of synapses. So, the organisms don’t have enough time to think. Or, it is also defined as the spontaneous, automatic and mechanical response to external stimuli which acts on the specific receptor.
Examples:- beating of heart, blinking of eyes, knee jerk reflex action, upward and downward movement of diaphragm during respiration. In knee- jerk reflex, a gentle strike below the knee cap, while sitting with free hanging legs then it shows the movement i.e it kicks the leg forward.
Reflex arc:- The path travelled by an electric impulse in a reflex action is called reflex arc. It consists of five parts:
1. A specific receptor:- It receives a stimulus and sets up a sensory impulse.
2. An afferent nerve:- it brings the sensory impulse from the receptors to the central nervous system.
3. Brain or spinal cord, are the portion of CNS which analyse and interpret the sensory impulse and set up an appropriate motor impulse.
4. An efferent nerve:- it carries the motor impulse from CNS to specific modulator and results in specific response to stimuli for the immediate action.
Add Comment