Golgi tendon organ
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| Golgi tendon organ | |
|---|---|
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| Organ of Golgi (neurotendinous spindle) from the human tendo calcaneus. | |
| Gray's | subject #233 1061 |
| Dorlands/Elsevier | o_06/12595597 |
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Overview
The Golgi organ (also called Golgi tendon organ, neurotendinous organ or neurotendinous spindle), is a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibres into the tendons of skeletal muscle.
The Golgi organ should not be confused with the Golgi Apparatus, which is an organelle in the eukaryotic cell, or the Golgi stain, which is an histologic stain for neuron cell bodies.
Anatomy
The body of the organ is made up of strands of collagen that are connected at one end to the muscle fibres and at the other merge into the tendon proper. Each tendon organ is innervated by a single afferent type Ib sensory fiber that branches and terminates as spiral endings around the collagen strands. The Ib afferent axon is a large diameter, myelinated axon. Each neurotendinous spindle is enclosed in a fibrous capsule which contains a number of enlarged tendon fasciculi (intrafusal fasciculi). One or more nerve fibres perforate the side of the capsule and lose their medullary sheaths; the axis-cylinders subdivide and end between the tendon fibers in irregular disks or varicosities (see figure).
Function
During muscle contraction the strands of collagen are stretched as the muscle shortens. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the axon is depolarized and fires nerve impulses up to the central nervous system via the spinal cord. The action potential frequency signals the force being developed within the muscle.
This sensory feedback plays an important role in spinal reflexes and in the central control of muscle contraction. Specifically, it is postulated that because a Golgi tendon organ exists in serial connection with muscle fibers, it can measure the tension that each muscle contraction builds up. The Ib afferent axon synapses with interneurons within the spinal cord and also relays information to the brain. One of the main spinal reflexes receiving an input from the Ib afferent is the autogenic inhibition reflex, which is involved with the regulation of the force profile of on-going muscle contractions.
The ascending or afferent pathways to the cerebellum are the dorsal and ventral spinocerebellar tracts and are involved in the cerebellar regulation of movement.
History
It was once believed that Golgi tendon organs were responsible for the clasp-knife reflex observed in spinal cord-injured patients. This theory has been rejected in favor of one that explains the reflex with free nerve endings.
See also
Source
This article incorporates text or images from the public domain Gray's Anatomy, Lea & Febiger, 1917 edition.
External links
- Golgi+tendon+organ at eMedicine Dictionary
- http://ami.usc.edu/projects/ami/projects/bion/musculoskeletal/golgi_tendon_organ.html
- http://www.lib.mcg.edu/edu/eshuphysio/program/section8/8ch3/s8ch3_11.htm
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
