In a healthy adult,a well-placed tap on the knee will result in a:

Question

Quizplus · Accepted Answer

When the knee is tapped, it causes a sudden stretch of the patellar tendon and quadriceps femoris muscle which activates the muscle spindles. These spindles then send a sensory signal to the spinal cord, which in turn, triggers a reflex arc causing the contraction of the quadriceps femoris muscle to extend the knee joint. Therefore, choice C which describes a stretch of the tendon and quadriceps femoris muscle and stimulation of the muscle spindles is the best answer. Choice A only describes the muscle contraction and stimulation of muscle spindles, and choice B and D do not accurately describe the mechanism of the knee-jerk reflex.

In a Healthy Adult,a Well-Placed Tap on the Knee Will