21 Oct
Why does your hand move without thinking?
If you accidentally touched a very hot kettle, your hand would instantly jerk away, without conscious your part. This kind of unlearned, involuntary reaction to a stimulus is called a reflex. Reflexes are simple, inborn, automatic responses of some parts of the body. The entire reflex, from touching the kettle to withdrawing your hand, occurs in a fraction of a second, because it involved transferring information between only three neurons. In comparison, it takes much longer before you can yell “ouch”. By the time you can yell your hand has already withdrawn from the kettle.
In reflexes, message is transmitted directly from sensory to motor neuron forming what is called a sensory-motor are, which causes the person to react even before such messages reach the cerebral cortex.
Reflexes have a significant role in everyday behavior, whether learned or unlearned – the protection of the organism. The papillary reflex or the narrowing of the pupils of the eye in response to excessive illumination, the gagging reflexes when an object is placed on the back of the tongue is examples of protective reflexes. There are also reflexes of the spinal cord like the knee jerk and the flexion of extension reflexes.
