This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
[{'content': 'Gamma neurons innervate: \nSelect and explain. \nA. Extrafusal muscle fibers, B. Intrafusal muscle fibers, C. Primary motor innervations to skeletal muscles, D. Inhibit antagonistic muscles', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Intrafusal muscle fibersa. In addition to the alpha motor neurons that excite contraction of the skeletal muscle fibers, about one half as many much smaller gamma motor neurons are located along with the alpha motor neurons in the anterior horns.b. These transmit impulses through type-A gamma fibers, averaging 5 microns in diameter, to very small, special skeletal muscle fibers called intrafusal fibers, present in the muscle spindle.', 'role': 'assistant'}]