Assuming all sensory, motor, and reflex pathways are intact, muscle contraction can be caused by stimulation of which of the following types of neurons?
A)Alpha motor neurons
B)Gamma motor neurons
C)Type 1a sensory endings from a nuclear bag fiber
D)All of the above

Question

Quizplus · Accepted Answer

All three options listed (alpha motor neurons, gamma motor neurons, and type 1a sensory endings from a nuclear bag fiber) are involved in muscle contraction. The alpha motor neurons are responsible for activating extrafusal muscle fibers (the main muscle fibers responsible for generating force), while gamma motor neurons are responsible for activating intrafusal muscle fibers (specialized muscle fibers found within muscle spindles). Type 1a sensory endings from nuclear bag fibers are sensory receptors that detect changes in muscle length and trigger a reflex contraction of the same muscle to help maintain posture and balance. Therefore, activation of any of these neurons can result in muscle contraction.

Assuming All Sensory, Motor, and Reflex Pathways Are Intact, Muscle