Which mechanism helps prevent injury by inhibiting the muscle during contraction when a slow stretch is applied?

• A. Muscle spindles
• B. Pacinian corpuscles
• C. Golgi tendon organs
• D. Joint receptors

Answer: (C)

When a muscle contracts and tension increases, the Golgi tendon organs at the muscle–tendon junction detect that force. They send Ib afferent signals to the spinal cord, which activate inhibitory interneurons that dampen the activity of the motor neurons to that same muscle. The result is autogenic inhibition—the muscle relaxes a bit to prevent injury from excessive tension, especially during a slow stretch when the tendon experiences sustained load. This protective mechanism helps avoid tearing or damaging the muscle-tendon unit.

For context, muscle spindles respond to stretch by triggering contraction to resist length change, not inhibition. Pacinian corpuscles sense rapid pressure or vibration, and joint receptors provide information about joint position, neither of which directly mediate this protective muscle-inhibition response during a slow stretch.