Reflex Arc

Biology
Concept: Reflex Arc

Reflex arc is the pathway through which the nerve impulse (generated due to the stimulus )travels throughout the nerves. The receptors gather stimulus and convert them into electrical impulse . This electrical impulse travels through sensory nerve to reach the spinal cord. Spinal cord processes the impulse quickly through relay neuron and then replies through the motor nerve, which affects the effector organ.

This entire process is very fast, so fast that we don't even realize when the reaction started and when it finished.



Touching a flame is an urgent and dangerous situation for us, or in fact, for any
animal! How would we respond to this? One seemingly simple way is to
think consciously about the pain and the possibility of getting burnt,
and therefore move our hand. An important question then is, how long
will it take us to think all this? Actually we do not have enough time to think and react. If we think before acting, we wont have enough time to save our hand from burning.

Therefore, actions which require urgent attention, cannot be carried out by brain directly. These involuntary actions (without our will) are called Reflex Actions. Although, after the reflex action has been completed, the brain realizes and acts accordingly. Like we react by saying "Oh! that was too hot". Saying these words are a function of brain, as they have come after much thought. But the reflex action itself isn't a function of brain.

So we conclude that, all stimuluses pass through spinal cord, while on their way to brain. Only those impulses which require urgent attention, are taken care by the spinal cord (through reflex arc) the rest are done by brain only.

Some Other Examples of Reflex Actions that occur in our daily lives:

Here in the above video, the knee jerk is a result of reflex action, the movement of her leg is unintentional, it is involuntary.



Similarly, when bright light is focussed on the eye, the pupil will constrict, so as to avoid damage to the retina because of excess light. This is not in our control so it is a reflex action.