When a muscle is rapidly stretched, which sensory receptors are activated?

When a muscle is rapidly stretched, the primary sensory receptors that come into play are the muscle spindles. These receptors are specially designed to detect changes in the length of a muscle and the speed of that change. When a stretch occurs, muscle spindles send signals to the central nervous system, which helps initiate a reflex that can cause the muscle to contract, acting as a protective mechanism against excessive stretching.

The Golgi tendon organs are also relevant but generally respond to changes in tension within the muscle rather than stretch. While both types of receptors play critical roles in proprioception and balancing muscle activity, the immediate response to a rapid stretch primarily involves muscle spindles.

Joint receptors contribute to the perception of joint position and movement but are not directly responsible for the response to muscle stretching.

Thus, during a rapid stretch, muscle spindles are activated primarily, but Golgi tendon organs do play a secondary supporting role in overall muscle function and coordination. This synergy is why both muscle spindles and Golgi tendon organs are considered relevant, making the response inclusive of both receptors when addressing muscle dynamics during rapid stretches.