Ravi withdraw his hand upon touching the hot pan. explain the phenomena with the of a block diagram

The given case is an example of reflex action.

The reflex action is an instant involuntary response to a stimuli, which can cause damage. The reflex action takes place through the processing of message through a reflex arc, this reflex arc lack the involvement of brain and the processing of the stimulus takes place in the spinal cord.

In this case, the sensory receptors detects the stimuli and transfer the message to the relay neuron present in the spinal cord through the sensory neuron. The relay neuron transfer the action message to the effector muscles present at the site of stimulus with the help of motor neurons.

Given below is a block diagram of reflex action.