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Golgi tendon reflex

The Golgi tendon reflex[1] (also called inverse stretch reflex, autogenic inhibition,[2] tendon reflex[3]) is an inhibitory effect on the muscle resulting from the muscle tension stimulating Golgi tendon organs (GTO) of the muscle, and hence it is self-induced. The reflex arc is a negative feedback mechanism preventing too much tension on the muscle and tendon. When the tension is extreme, the inhibition can be so great it overcomes the excitatory effects on the muscle's alpha motoneurons causing the muscle to suddenly relax.[1] This reflex is also called the inverse myotatic reflex,[4] because it is the inverse of the stretch reflex.

GTOs' inhibitory effects come from their reflex arcs: the Ib sensory fibers that are sent through the dorsal root into the spinal cord to synapse on Ib inhibitory interneurons that in turn terminate directly on the motor neurons that innervate the same muscle. The fibers also make direct excitatory synapses onto motoneurons that innervate the antagonist muscle.[2] Note that the disynaptic reflex pathway does not always have inhibitory effects: under certain conditions, GTO stimulation can result in motoneuron excitation.[5]

Besides protecting against too much tension on the muscle and tendon, the tendon reflex may help spread muscle load throughout the muscle fibers, thereby preventing damage to isolated fibers.[1][3] Whereas the stretch reflex regulates muscle length, the tendon reflex helps regulate muscle force.[2] It helps maintain steady levels of tension and stable joints to counteract effects that reduce muscle force (such as fatigue).[6] Because the Ib inhibitory interneurons receive convergent multisensory inputs and descending pathways, they may allow fine control of muscle forces,[5] and may be better at protective functions.[6] Also, because the Ib fibers connect widely with the motoneurons innervating muscles working on different joints, the Golgi tendon reflex forms part of reflex networks that control movements of the whole limb.[5]

  1. ^ a b c Hall & Guyton (2006), Golgi Tendon Reflex, pp. 679–680
  2. ^ a b c Barrett et al (2010), INVERSE STRETCH REFLEX, pp. 162–163
  3. ^ a b Saladin (2018), The Tendon Reflex, pp. 498–499
  4. ^ Michael-Titus, Adina T; Revest, Patricia; Shortland, Peter, eds. (2010). "Chapter 9 - Descending Pathways and Cerebellum". Systems of The Body: The Nervous System – Basic Science and Clinical Conditions (2nd ed.). Churchill Livingstone. Golgi tendon organs, p. 166. ISBN 9780702033735.
  5. ^ a b c Pearson & Gordon (2013), Convergence of Inputs on Ib Interneurons Increases the Flexibility of Reflex Responses, p. 799
  6. ^ a b Purves et al (2018a), The Spinal Cord Circuitry Underlying the Regulation of Muscle Force, pp. 370–371

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