Neuromuscular system: Golgi tendon organ.

The idea

The Golgi tendon organ is a proprioceptor lying within the tendon close to where it joins the muscle. It detects the tension developed by the muscle, whether that tension arises from active contraction or from passive stretch, and it signals this information to the central nervous system. When tension becomes excessive, the resulting afferent feedback triggers an inhibitory response that reduces the force produced by the muscle, which is described as autogenic inhibition. This protective reflex helps to limit the risk of injury to the muscle and its tendon. In multiple-choice assessment you must distinguish the Golgi tendon organ, which monitors tension, from the muscle spindle, which monitors the rate and extent of muscle length change.

What earns the marks

• Identifies the Golgi tendon organ as a proprioceptor located in the tendon near the musculotendinous junction.
• States that it detects tension generated within the muscle and tendon rather than muscle length.
• Explains that afferent signals travel to the central nervous system to inform it about the level of tension.
• Describes autogenic inhibition, in which excessive tension leads to reduced muscle force output as a protective response.
• Distinguishes the Golgi tendon organ from the muscle spindle, which detects changes in muscle length and the rate of that change.

Common mistakes and how to put them right

• Confusing the Golgi tendon organ with the muscle spindle.

  Put it right: The Golgi tendon organ monitors tension in the tendon, whereas the muscle spindle monitors length and rate of change of length.

• Believing the Golgi tendon organ directly causes the muscle to contract.

  Put it right: It provides sensory feedback that can inhibit contraction when tension is excessive.

• Thinking the receptor is located in the muscle belly.

  Put it right: It lies in the tendon close to the musculotendinous junction.

• Assuming the response always increases force.

  Put it right: The protective response reduces force output when tension is judged to be too high.

Exam tips

• Read each option carefully and eliminate any that describe detection of muscle length, because that is the role of the muscle spindle.
• Link the receptor to its protective function so that tension detection and autogenic inhibition are recalled together.
• Use precise terminology such as proprioceptor, tension and afferent feedback rather than vague phrases like 'senses movement'.