All are true regarding withdrawal reflex except:
Ref:1. Guyton & Hall. Flexor Reflex and the Withdrawal Reflexes. In: Textbook of Medical Physiology.12th ed. Philadelphia: Saunders Elsevier; 2012. p 661-663.2. W F Ganong. Excitable Tissue: Nerve . In: Review of Medical Physiology. 21st ed. California: McGraw-Hill Companies; 2003Explanation:in the spinal or decerebrate animal, almost any type of cutaneous sensory stimulus from a limb is likely to cause the flexion, thereby withdrawing the limb from the stimulating object. This is called the flexor reflexIn its classic form, it is also called a nociceptive reflex, or simply a pain reflex. Pain is mainly earned through type III, IV fibers lie, Aa, C fibers)Signals of the reflex traverse through many neurons (poly synaptiC. hence, reflex has long latency. These signals involve the following basic types of circuits:Diverging circuits to spread the reflex to the necessary muscles for withdrawalCircuits to inhibit the antagonist muscles, called reciprocal inhibition circuitsCircuits to cause after-discharge lasting many fractions of a second after the stimulus is overNumberOriginFiber TypeIaMuscle spindle, annulo-spiral endingAIbGolgi tendon organAIIMuscle spindle, flower-spray ending: touch, pressureAIIIPain and cold receptors: some touch receptorsAIVPain, temperature, and other receptors Dorsal rootCFig: Polysynatic reflex Withdrawal ReflexIt is a typical polysynaptic reflex that occurs in response to a noxious and usually painful stimulation of the skin or subcutaneous tissues and muscle.The response is flexor muscle contraction and inhibition of extensor muscles, so that the part stimulated is flexed and withdrawn from the stimulus.When a strong stimulus is applied to a limb, the response includes not only flexion and withdrawal of that limb but also extension of the opposite limb. This crossed extensor response is properly part of the withdrawal reflex.Withdrawal reflexes are prepotent; i.e they preempt the spinal pathways from any other reflex activity taking place at the moment. Local SignThe exact flexor pattern of the withdrawal reflex in a limb varies with the part of the limb that is stimulated.This dependence of the exact response on the location of the stimulus is called local sign, in Fractionation & OcclusionSupramaximal stimulation of any of the sensory nerves from a limb never produces as strong a contraction of the flexor muscles as that elicited by direct electrical stimulation of the muscles themselves.This indicates that the afferent inputs fractionate the motor neuron pool; ie, each input goes to only part of the motor neuron pool for the flexors of that particular extremity.If all the sensory inputs are dissected out and stimulated one after the other, the sum of the tension developed by stimulation of each is greater than that produced by direct electrical stimulation of the muscle or stimulation of all inputs at once.This indicates that the various afferent inputs share some of the motor neurons and that occlusion occurs when all inputs are stimulated at once.
Has long latency
Poly synaptic
Carried by la fibers
Has after-discharge
Nerve Physiology