Neural Control of Movement Part III: Golgi Tendon Organs

A couple of weeks ago, we talked about a special type of proprioceptive receptor called muscle spindles.  Muscle spindles detect changes in muscle length and velocity of lengthening, and send signals to the CNS.  This helps the nervous system know about changes in joint angles and muscle length, and can help protect the muscle from lengthening too much and too fast.

Another type of proprioceptive receptor found in muscle (actually between the muscle and tendon) is the Golgi Tendon Organ (GTO).  These receptors are sensitive to changes in muscular force.  Whenever a muscle contracts (shortens), tension is developed within the muscle and tendon, which activates the GTO, causing it to send signals to the CNS.  Thus, the GTO provides feedback to the CNS about the amount of force a muscle is producing.  If a muscle is producing too much force, and is at risk of injury, the CNS can send inhibitory signals back down to the muscle so it will stop contracting and relax, thus reducing the amount of force.  Unlike the muscle spindles, which are are sensitive to changes in muscle length and the rate of change, GTOs are only sensitive to changes in muscle force, not the rate of change.

So, the muscle spindles send information to the CNS about  muscle length and the velocity of lengthening, and GTOs send information about muscular force.  This information allows the nervous system to make quick adjustments so we can move more efficiently and safely.