What is reflex action? How it differs from normal functions of the brain?

You need to keep the conditions inside your body constant.

Doing this is called homeostasis. Small changes inside your body can cause its cells to be damaged or destroyed. Yet, there are big changes going on outside your body.

You need to detect a change in the environment (a stimulus) and react to the change (a response) in a way that maintains homeostasis. When you do this without thinking, it is called a reflex.

For example, when we touch a hot object, we withdraw our hand immediately without thinking. The sensory nerves that detect the heat are connected to the nerves that move the muscles of the hand. Such a connection of detecting the signal from the nerves (input) and responding to it quickly (output) is known as reflex arc. Reflex arcs are formed in the spinal cord but the information is still sent to the brain. The brain doesn’t have a significant response to it.

An involuntary response on stimulation of the peripheral nervous system which requires the involvement of a part of the central nervous system is called reflex action. The afferent neuron receives a signal from a sensory organ. It then transmits the impulse to the spinal cord via the dorsal root. The spinal cord sends the processed signal to the effectors through the efferent neuron forming a reflex arc

It differs from the normal functions of the brain as brain need some time to react to anything but reflex are so fast they do not even think.

The automatic response of the body to a stimulus is called a reflex action. The response comes out within seconds. Most of the decisions, in reflex action are taken by the spinal cord not the brain. The brain thinks what to do but in reflex action, the response just comes out within a few seconds.