Question

multiple choice question

which correctly describes a stretch reflex?

• it is primarily mediated by the brain.
• it cannot occur is the spinal cord is severed.
• it is strictly a spinal reflex.

Explanation:

Analyze the definition of a stretch reflex

Using the Stretch Reflex Physiology knowledge point
A stretch reflex (such as the patellar reflex) is an involuntary, automatic muscle contraction in response to passive stretching of the muscle. It is a monosynaptic reflex arc that functions to maintain muscle tone and protect muscles from overstretching.

Evaluate the neural pathway

Using the Spinal Reflexes knowledge point
Spinal reflexes are integrated and processed entirely within the spinal cord, meaning they do not require conscious input or mediation from the brain to occur. Therefore, the statement "It is primarily mediated by the brain" is incorrect, while "It is strictly a spinal reflex" is correct.

Assess the effect of spinal cord injury

Using the Spinal Reflexes knowledge point
Because the reflex arc is completed entirely within the local segment of the spinal cord (sensory neuron to motor neuron), it can still function locally even if the spinal cord is severed higher up (which disconnects the spinal cord from the brain). Thus, the statement "It cannot occur is the spinal cord is severed" (typographical error in the prompt for "if") is incorrect.

Answer:

• It is primarily mediated by the brain.
• It cannot occur is the spinal cord is severed.
• It is strictly a spinal reflex. (Correct answer)