The "knee jerk" or stretch reflex is due to the activation of the muscle spindle.

Question

Quizplus · Accepted Answer

The knee jerk reflex, also known as the patellar reflex, is a type of stretch reflex that occurs when the patellar tendon is tapped, causing the quadriceps muscle to contract and the leg to momentarily straighten. This reflex is due to the activation of the muscle spindle, which senses changes in muscle length and sends a signal to the spinal cord, which in turn sends a signal back to the muscle causing it to contract. Therefore, the knee jerk reflex is properly attributed to the activation of the muscle spindle, making option A the correct answer.

The "Knee Jerk" or Stretch Reflex Is Due to the Activation