How do you withdraw your hand from a painful stimulus?

Here we speak about the withdrawal reflex, and in particularly the flexor reflex which affects the muscle of a limb. This is a polysinaptic relfex because it can involve simultaneously the stimulation of some muscle groups and the inhibition of others. For example, the stimulus of a hot frying pan or stove will cause the contraction of the flexor muscles of the arm, thus we withdraw the hand from the pan.  Events in an arc reflex begin at a receptor and ends at a peripheral effector (muscle fibre or gland cell). First of all, the arrival of the stimulus activates the nociceptors in the hand. The sensory neurons or the afferent neurons will be stimulated and will arrive in the gangion of the dorsal root. Then, they will activate the interneurons distributed within the ventral grey horn of the spinal cord, which will stimulate the motor neurons in the anterior grey horn. The alpha motor neurons will be activated. This neuron controls all the flexor muscles of the limb, and so the flexors will be contracted and the extensors will be inhibited (opposing muscles must relax to permit movement). We can see here why the reflex is polysynaptic. The interneurons controlled several muscle groups by producing either excitatory or inhibitory postsynaptic potentials. The peripheral effector will induce then the wanted response.