Which statement about the knee-jerk reflex is true?
A) It requires a decision to move the leg.
B) It requires stretch receptors that fire action potentials in motor neurons.
C) It involves motor neurons conducting action potentials to the leg muscles.
D) It requires interneurons carrying signals to the brain.
E) It involves output leaving the dorsal horn of the spinal cord.

Question

Quizplus · Accepted Answer

The knee-jerk reflex is a simple reflex that does not involve a decision to move the leg. Instead, it is a spinal reflex that is triggered by stretch receptors in the muscle spindle of the quadriceps muscle. When the muscle is stretched, sensory neurons carry the signal to the spinal cord, where synapses occur with motor neurons that innervate the same muscle. This results in contraction of the quadriceps muscle and a corresponding extension of the leg. Therefore, the correct statement is that the knee-jerk reflex involves motor neurons conducting action potentials to the leg muscles.

Which Statement About the Knee-Jerk Reflex Is True