Final answer:
The quadriceps reflex checks the functioning of the lower motor neuron components involving the femoral nerve, and is tested by striking the patellar tendon with a rubber mallet to cause a contraction of the quadriceps muscle. A normal reflex involves an extension of the lower leg and indicates properly functioning neural pathways; abnormalities can signify potential damage or lesions within the spinal cord or nerves.
Step-by-step explanation:
The quadriceps reflex, also known as the patellar reflex or knee reflex, is a deep tendon reflex that checks the functioning of the lower motor neuron component of the reflex arc. This reflex evaluates the sensory and motor pathways of the femoral nerve. To test the quadriceps reflex, a rubber mallet is used to strike the patellar tendon which is located just below the kneecap (patella). The strike should cause a quick stretch in the quadriceps muscle, the large muscle group at the front of the thigh.
Upon striking the tendon, an impulse travels through the dorsal root of the spinal cord, then synapses directly on the ventral horn motor neuron, which activates the quadriceps muscle to contract. This contraction causes the lower leg to extend in a kicking motion. The reflex is physiologically valuable for maintaining posture and balance as it helps to compensate for sudden changes in muscle length.
In the context of a neurological exam, a normal quadriceps reflex suggests that the lower motor neurons, which include components of the spinal cord and nerves that communicate with muscles, are functioning properly. Absence or decrease of this reflex can indicate a possible lesion or damage in the relevant spinal segments or peripheral nerves. The quadriceps reflex is an essential component of a physical examination and is beneficial in assessing the integrity of the nervous system.