Interneurons excite alpha motor neurons, which in turn excite the muscle. Alpha motor neurons send efferent messages to the quadriceps, while parallel efferent messages to the hamstrings are reduced. Alpha motor neurons activate the quadriceps. Once the quadriceps have contracted, alpha motor neurons inhibit the hamstrings. Alpha motor neurons send efferent messages to excite the quadriceps and the hamstrings are reduced.

The question is incomplete. The complete question is as follows;

Examine and characterize the two motor pathways in the stretch patellar reflex.

A) Alpha motor neurons send efferent messages to the quadriceps, while parallel efferent messages to the hamstrings are reduced.

B) Alpha motor neurons send efferent messages to excite the quadriceps and the hamstrings are reduced.

C) Alpha motor neurons activate the quadriceps. Once the quadriceps have contracted, alpha motor neurons inhibit the hamstrings.

D) Interneurons excite alpha motor neurons, which in turn excite the muscle.

Alpha motor neurons send efferent messages to the quadriceps, while parallel efferent messages to the hamstrings are reduced.

Explanation:

Neuron is the structural and functional unit of the nervous system. The neurons can be classified as sensory neuron, motor neuron and interneuron based on their function.

The knee reflex is known as patellar reflex that involves in the movement of knees and stretching of patellar tendon. The efferent message is send by alpha motor neuron that are located in the anterior horn of the spinal cord. This send to quadriceps that results in the muscle contraction. In this process, the hamstrings messages are reduced that plays an important role in patellar reflex.

Thus, the correct answer is option (A).