What parts of the body are involved in the pain withdrawal reflex?

Question

What parts of the body are involved in the pain withdrawal reflex?

Answer 1

The Brain!

Answer 2

actually it's not the brain that is involved in the withdrawal reflex...you see, the brain is involved in reception, analysis and (voluntary) production of signals...so if you put your hand on a hot stove, you don't analyze the pain before withdrawing your hand, and you don't choose to withdraw your hand or keep it on the stove...so the reflex is involuntary.

it is the spinal cord that is involved in this reflex...this reflex is polysynaptic, that is, it involves 2 synapses between the sensory neurone and motor neurone. so when you put your hand on the stove, the sensory neurone will transmit the signal (pain) to an intermediate neurone via a synapse, then the intermediate neurone will transmit the signal to the motor neurone via another synapse (total = 2 synapses).

all these neurones (sensory, intermediate and motor) are involved only in the spinal cord and do not pass to the brain.

another example of reflex involving the spinal cord is the knee-jerk reflex (like when you hit the tendon of your knee). however this reflex is monosynaptic in contrary to the pain withdrawal reflex.