In the knee jerk reflex shown in the figure, which of the following components of the reflex arc serves as the sensory receptor?
A)muscle spindle
B)gray matter of spinal cord
C)sensory neuron
D)motor neuron
E)quadriceps femoris muscle

Question

In the knee jerk reflex shown in the figure, which of the following components of the reflex arc serves as the sensory receptor? 
A)muscle spindle 
B)gray matter of spinal cord 
C)sensory neuron 
D)motor neuron 
E)quadriceps femoris muscle

Quizplus · Accepted Answer

In the knee jerk reflex, the sensory receptor is the muscle spindle, which is located in the quadriceps femoris muscle. When the quadriceps muscle is stretched, the muscle spindle sends a signal to the spinal cord via sensory neurons, which then synapse with motor neurons in the gray matter of the spinal cord. The motor neurons then send an impulse back to the quadriceps muscle, causing it to contract and resulting in the knee jerk reflex. Therefore, choice A (muscle spindle) is the best choice for the sensory receptor in this reflex arc.

In the Knee Jerk Reflex Shown in the Figure, Which