Which of the following occurs last (patellar tendon reflex)?
A)The effector organ contracts.
B)The action potential travels along the efferent neuron to the quadriceps femoris.
C)The action potential travels along the sensory neuron to the spinal cord.
D)The muscle receptors of the quadriceps femoris are stimulated when the patellar ligament is stretched.

Question

Quizplus · Accepted Answer

The patellar tendon reflex, also known as the knee-jerk reflex, is a monosynaptic reflex arc that occurs as follows: when the patellar ligament is tapped, it stretches the quadriceps femoris muscle, which activates its muscle spindle receptors. These receptors in turn send a sensory signal (afferent neuron) to the spinal cord. Within the spinal cord, the sensory neuron synapses directly onto the motor neuron (efferent neuron) that controls the quadriceps femoris muscle. The motor neuron then sends an action potential to the muscle fibers, causing them to contract and extend the lower leg. Therefore, the correct sequence of events is: C → B → D → A, which means that the effector organ (quadriceps femoris) contracts last.

Which of the Following Occurs Last (Patellar Tendon Reflex)