Question

In the stretch reflex, this structure is stretched and sends impulses via the somatic sensory neuron to the spinal cord.

a) Axon
b) Cell membrane
c) Dendrite
d) Muscle spindle

Answer 1

The structure stretched in the stretch reflex, which sends signals to the spinal cord, is the muscle spindle, leading to muscle contraction (Option D).

Step-by-step explanation:

In the stretch reflex, the structure that is stretched and sends impulses via the somatic sensory neuron to the spinal cord is the muscle spindle. This reflex mechanism involves a muscle spindle receptor that, when the skeletal muscle is stretched, becomes activated.

An axon from this receptor structure sends signals that lead to the direct contraction of the muscle, with a collateral of the muscle spindle fiber inhibiting the motor neuron of the antagonist muscles. This process is crucial for maintaining constant muscle length and is exemplified by the knee j*rk reflex in clinical exams.

Thus, the correct option is D.

Answer 2

In the stretch reflex, the structure that is stretched and sends impulses via the somatic sensory neuron to the spinal cord is the D. muscle spindle.

Step-by-step explanation:

The muscle spindle is the structure that is stretched and sends impulses via the somatic sensory neuron to the spinal cord in the stretch reflex. The muscle spindle is a specialized sensory receptor that is found within the skeletal muscle. It is sensitive to changes in muscle length and detects stretching of the muscle.

When the muscle spindle is stretched, it sends impulses through the somatic sensory neuron to the spinal cord, which then activates the appropriate motor neurons to cause a muscle contraction. Therefore the correct answer is D. muscle spindle.