Answer:
A reflex action is defined as an involuntary action of body in response to a stimulus, which protects the body from any harmful conditions including touching open flame.
A reflex action follows a sequence of action that helps in involuntary action, tha include the stimulus, receptor in the skin, the neurons (sensory, relay and motor neurons), the effector(muscle) and resposne of body to stimulus.
In the reflex action when a person pull his/her arm away from an open flame, the stimulus will be the hot flame that send a signal to the nervous system.
The sensory receptor found in the dermis or epidermis of skin called cutaneous receptors, senses the temperature change.
Then the sensory neuron comes in action which sends electrical impulses to a relay neuron (located in spinal cord) and relay neuron sends impulse to motor neuron.
Motor neuron sends that electrical impulses to a muscle which act as an effector which allows muscle to contracts to move hand away.
So, at the end the body resposnes to move hand aways from the open flame.