The patellar or kneejerk reflex involves A stimulatory nerv

The patellar or knee-jerk reflex involves ________.

A. stimulatory nerve impulses to the hamstrings and inhibitory impulses to the quadriceps

B. stimulatory nerve impulses to the quadriceps and inhibitory impulses to the hamstrings

C. inhibitory nerve impulses to both quadriceps and the hamstrings

D. stimulatory nerve impulses to both quadriceps and the hamstrings

Solution

Answer: B. stimulatory nerve impulses to the quadriceps and inhibitory impulses to the hamstrings

Reason:

Patellar reflex is a simple stretch reflex (somatic reflex). Patellar reflex can be tested by knee jerk in which stimulatory nerve impulses to the quadriceps (via cholinergic stimulation) and inhibitory impulses to the hamstrings occurs simultaneously. Person should be asked to sit on a bench with hanging legs freely, and tap the patellar ligament just below the knee with the reflex hammer. This excites the muscle spindle of quadriceps that is innervated by femoral nerve. Patellar reflex is an example of monosynaptic reflex, it does not contain interneuron (contains 2 neurons in a chain).

Femoral nerve (afferent fibres) carries the information to the lumbar region (integration center) of the spinal cord. The efferent fibres of the femoral nerve carry the motor information back to the quadriceps muscle (effector). The knee jerk reflex (patellar reflex) arises at the level of L2 through L4 of the spinal cord.