Golgi Tendon Organ
Introduction[edit | edit source]
Golgi tendon organs (GTOs) are proprioceptors that are located in the tendon adjacent to the myotendinous junction.
Image 1: Golgi Tendon Organ (neurotendinous spindle) from the human tendo calcaneus.
- In man, some 10 to 20 muscle fibres are connected to one tendon organ.
- A typical tendon organ in limb muscles has an ending of about 0.5 mm in length. The endings are supplied by Ib afferent fibres (thinner than Ia) of high conduction velocity.
- The GTO are nearly as common in most muscles as muscle spindles.
In contrast to muscle spindles, the Golgi tendon organ lies in series with skeletal muscle fibres and therefore discharges during passive stretching of the muscle as well as when the tendon is stretched by the contraction of the muscle. Accordingly, the tendon organ is considered to be a muscle tension receptor rather than a muscle stretch receptor. 
Motor Control[edit | edit source]
Two feedback systems (both involving muscle afferents) regulate force and muscle length through reflexes. Muscle spindle afferents transduce (ie convert the message into another form) muscle length, whereas GTO afferents transduce muscle force.
Image 2: Golgi tendon organ schematic
- GTOs lie in series with the extrafusal fibers and receive no motor innervation.
- They send force information to the spinal cord, where interneurons receive input from the brain that specifies the amount of force that a muscle should produce.
- If that muscle's force level exceeds this set point, the GTO inputs inhibit the alpha motor neurons innervating that muscle, which lowers the force produced unless some other mechanism cancels that signal.
Postural Stability and GTOs[edit | edit source]
GTOs are mechanoreceptors that provide output encoding the level of tensile load applied to the tendon.
For this reason, GTOs, particularly those in the lower-limb extensors, are critical for sensing the forces exerted to resist imposed loads or the force of gravity acting on the body and regulating extensor activity required for maintaining vertical support and postural stability.
These receptors are located in series between the muscle fibers and the collagen strands that compose the tendon.
- Each GTO is innervated by a single myelinated Ib afferent. Muscle contraction straightens the collagen fibers surrounding the GTO and compresses and depolarizes the sensory ending.
- Ib axons are fast conducting (72–120 m/s), bifurcate when entering the spinal cord, and send branches rostrally and caudally via the dorsal columns.
- Branches that enter the gray matter principally terminate in Rexed's laminae V–VII (Fig. 1.3C) and innervate premotor interneurons.
- This causes a reflex inhibition of the muscle (see below)..
Image 3: The dorsal column pathway is one of the neural pathways by which sensory information from the peripheral nerves is transmitted to the cerebral cortex. Conscious proprioception is transmitted in this pathway ie: Muscle spindles and Golgi tendon organs which detect muscle length and contraction changes contributing to fine motor control and axial position.
Relexes[edit | edit source]
A reflex action mediated by the Golgi tendon organs that is called the inverse stretch reflex. When the organs are stimulated by a prolonged stretch they cause the stretched muscle to relax. This reflex, which connects high force in the Golgi tendon organs with relaxation, is the opposite of the myotatic reflex (or stretch reflex), in which stretch elicits a reflex contraction. The myotatic reflex is caused by a stretching in the muscle spindle.
Physiotherapy[edit | edit source]
When people lift weights, the golgi tendon organ is the sense organ that tells how much tension the muscle is exerting. If there is too much muscle tension the golgi tendon organ will inhibit the muscle from creating any force (via a reflex arc), thus protecting the you from injuring itself. This works in concert with the muscle spindles that monitor muscle length.
GTOs are sensitive to changes in tension and rate of tension and, because they are located in the musculotendinous junctions, they are responsible for sending information to the brain as soon as they sense an overload. Static stretching is one example of how muscle tension signals a GTO response. When a low-force stretch is held for more than seven seconds, the increase in muscle tension activates the GTO, which temporarily inhibits muscle spindle activity (thus reducing tension in the muscle), and allows for further stretching.
Knowledge of GTOs and muscle spindles are important concepts in muscle stretches eg in PNF and static stretching.
Camillo Golgi[edit | edit source]
Winner of Nobel Prize for Physiology or Medicine, Camillo Golgi, discovered (one of his discoveries) the Golgi Tendon Organ. The contributions of Camillo Golgi (1843–1926) to the study of the nervous system are a pillar of modern neuroscience. The Golgi impregnation first offered to microscopic studies individual neurons and glial cells in their entirety, and has therefore laid the foundation of neurohistology and neuroanatomy, opening a new era in neuroscience. 
References[edit | edit source]
- Proske U. The Golgi tendon organ. Trends in Neurosciences. 1979 Jan 1;2:7-8.Available from: https://www.cell.com/trends/neurosciences/fulltext/0166-2236(79)90004-3(accessed 18.5.2021)
- Morimoto T, Takada K. The sense of touch in the control of ingestion. InNeurophysiology of Ingestion 1993 Jan 1 (pp. 79-97). Pergamon.Available from: https://www.sciencedirect.com/topics/neuroscience/golgi-tendon-organ(accessed 18.5.2021)
- Ramachandran VS. Encyclopedia of the Human Brain, Four-Volume Set. Academic Press; 2002. Available from: https://www.sciencedirect.com/topics/neuroscience/golgi-tendon-organ(Accessed 18.5.2021)
- MacKinnon CD. Sensorimotor anatomy of gait, balance, and falls. Handbook of clinical neurology. 2018 Jan 1;159:3-26.Available from:https://www.sciencedirect.com/topics/neuroscience/golgi-tendon-organ (accessed 18.5.2021)
- Feher JJ. Quantitative human physiology: an introduction. Academic press; 2017 Jan 2.Available from: https://www.sciencedirect.com/topics/neuroscience/golgi-tendon-organ(accessed 18.5.2021)
- Bentivoglio M, Cotrufo T, Ferrari S, Tesoriero C, Mariotto S, Bertini G, Berzero A, Mazzarello P. The original histological slides of Camillo Golgi and his discoveries on neuronal structure. Frontiers in neuroanatomy. 2019 Feb 18;13:3.Available: (accessed 18.5.2021)