[Campbell Biology P.1137] Which of the following statements accurately describes a component ... | Practice Question

Which of the following statements accurately describes a component or event in the knee-jerk reflex as depicted in Figure 49.5?

  • A: Sensory neurons convey information directly to motor neurons in the quadriceps muscle.
  • B: The hamstring muscle contracts to assist the quadriceps in jerking the lower leg forward.
  • C: Interneurons in the spinal cord inhibit motor neurons leading to the hamstring muscle.
  • D: The reflex is initiated by direct stimulation of the quadriceps muscle by the mallet.

Explanation

In the knee-jerk reflex, sensory neurons detect the stretch in the quadriceps and convey signals to the spinal cord. Within the spinal cord, interneurons inhibit motor neurons leading to the hamstring muscle, preventing its contraction and allowing the quadriceps to contract and extend the lower leg forward. The mallet initiates the reflex by tapping the tendon, causing a stretch, not direct muscle stimulation. Sensory information does not directly go to muscle motor neurons; it first processes through the spinal cord.