Gamma motor neurons innervate which fibers?

Gamma motor neurons innervate which fibers?

• A. Intrafusal fibers
• B. Extrafusal fibers
• C. Tendon fibers
• D. Cardiac fibers

Answer: (A)

Gamma motor neurons keep the muscle spindle sensitive by innervating intrafusal fibers inside the spindle. When they fire, these intrafusal fibers contract at their polar ends, maintaining tension in the spindle so its central sensory region can accurately detect stretch even as the muscle shortens or contracts. This sustains the appropriate feedback from the spindle to the nervous system (via Ia and II afferents) and supports reflexes and motor control. In contrast, the main force-producing skeletal muscle fibers, the extrafusal fibers, are innervated by alpha motor neurons. Tendon-related receptors and cardiac muscle are governed by different systems, not by gamma motor neurons.

Gamma motor neurons keep the muscle spindle sensitive by innervating intrafusal fibers inside the spindle. When they fire, these intrafusal fibers contract at their polar ends, maintaining tension in the spindle so its central sensory region can accurately detect stretch even as the muscle shortens or contracts. This sustains the appropriate feedback from the spindle to the nervous system (via Ia and II afferents) and supports reflexes and motor control.

In contrast, the main force-producing skeletal muscle fibers, the extrafusal fibers, are innervated by alpha motor neurons. Tendon-related receptors and cardiac muscle are governed by different systems, not by gamma motor neurons.