Question

multiple choice question

stretch reflexes are mediated primarily by which of the following?

• the brain
• the spinal cord
• the ans
• the pns

Explanation:

Define stretch reflexes

Using the Spinal Reflexes knowledge point
A stretch reflex (such as the patellar reflex) is an involuntary, rapid response to the stretching of a muscle, helping to maintain muscle tone and posture.

Identify the integration center

Using the Reflex Arc Physiology knowledge point
The sensory signal from the muscle spindle travels via an afferent fiber directly into the central nervous system, where it synapses directly with an alpha motor neuron. This integration occurs entirely within the gray matter of the spinal cord without requiring conscious input from the brain.

Evaluate the given options

• The brain: While the brain receives sensory information about the stretch, it is not the primary mediator of the immediate reflex loop.
• The spinal cord: This is the primary integration center where the sensory neuron synapses with the motor neuron.
• The ANS (Autonomic Nervous System): Stretch reflexes involve skeletal muscles, which are controlled by the somatic nervous system, not the autonomic system.
• The PNS (Peripheral Nervous System): The PNS contains the peripheral nerves that carry the signals, but the integration and mediation of the reflex arc itself occur within the central nervous system (specifically the spinal cord).

Answer:

• The brain
• The spinal cord (Correct answer)
• The ANS
• The PNS