Golgi organ
Encyclopedia
The Golgi organ is a proprioceptive sensory receptor
organ that is located at the insertion of skeletal muscle fibers into the tendon
s of skeletal muscle
. It provides the sensory component of the Golgi tendon reflex
.
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 a histologic
stain for neuron
cell bodies
.
that are connected at one end to the muscle fibers 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, myelin
ated 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).
When the muscle generates force, the sensory terminals are compressed. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the Ib axon is depolarized and fires nerve impulses
that are propagated to the spinal cord
. The action potential frequency signals the force
being developed by the 10 to 20 motor units within the muscle. This is representative of whole muscle force
The Ib sensory feedback
generates spinal reflexes and supraspinal responses which control muscle contraction. Ib afferents synapse
s with interneuron
s within the spinal cord that also project to the brain cerebellum and cerebral cortex. One of the main spinal reflexes associated with Ib afferent activity is the autogenic inhibition reflex, which helps regulate the force of muscle contractions. Tendon organs signal muscle force through the entire physiological range, not only at high strain.
During locomotion, Ib input excites rather than inhibits motoneurons of the receptor-bearing muscles and it also affects the timing of the transitions between the stance and swing phases of locomotion. The switch to autogenetic excitation is a form of positive feedback.
The ascending or afferent
pathways to the cerebellum
are the dorsal and ventral spinocerebellar tract
s. They are involved in the cerebellar regulation of movement.
, which protected the muscle and tendons from excessive force. However, the underlying premise was shown to be incorrect by James Houk and Elwood Henneman in 1967.
Sensory receptor
In a sensory system, a sensory receptor is a sensory nerve ending that responds to a stimulus in the internal or external environment of an organism...
organ that is located at the insertion of skeletal muscle fibers into the tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
s of skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
. It provides the sensory component of the Golgi tendon reflex
Golgi tendon reflex
The Golgi tendon reflex is a normal component of the reflex arc of the peripheral nervous system. In a Golgi tendon reflex, skeletal muscle contraction causes the muscle to simultaneously lengthen and relax. This reflex is also called the inverse myotatic reflex, because it is the inverse of the...
.
The Golgi organ should not be confused with the Golgi Apparatus
Golgi apparatus
The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named....
, which is an organelle in the eukaryotic cell
Eukaryotic Cell
Eukaryotic Cell is an academic journal published by the American Society for Microbiology. The title is commonly abbreviated EC and the ISSN is 1535-9778 for the print version, and 1535-9786 for the electronic version....
, or the Golgi stain
Golgi's method
Golgi's method is a nervous tissue staining technique discovered by Italian physician and scientist Camillo Golgi in 1873. It was initially named the black reaction by Golgi, but it became better known as the Golgi stain or later, Golgi method.Golgi' staining was famously used by Spanish...
, which is a histologic
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
stain for neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
cell bodies
Soma (biology)
The soma , or perikaryon , or cyton, is the bulbous end of a neuron, containing the cell nucleus. The word "soma" comes from the Greek σῶμα, meaning "body"; the soma of a neuron is often called the "cell body"...
.
Anatomy
The body of the organ is made up of strands of collagenCollagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
that are connected at one end to the muscle fibers 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, myelin
Myelin
Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...
ated axon. Each neurotendinous spindle is enclosed in a fibrous capsule
Fibrous membrane of articular capsule
The fibrous membrane of articular capsule is attached to the whole circumference of the articular end of each bone entering into the joint, and thus entirely surrounds the articulation....
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
]When the muscle generates force, the sensory terminals are compressed. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the Ib axon is depolarized and fires nerve impulses
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
that are propagated to the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. The action potential frequency signals the force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
being developed by the 10 to 20 motor units within the muscle. This is representative of whole muscle force
The Ib sensory feedback
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
generates spinal reflexes and supraspinal responses which control muscle contraction. Ib afferents synapse
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
s with interneuron
Interneuron
An interneuron is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways...
s within the spinal cord that also project to the brain cerebellum and cerebral cortex. One of the main spinal reflexes associated with Ib afferent activity is the autogenic inhibition reflex, which helps regulate the force of muscle contractions. Tendon organs signal muscle force through the entire physiological range, not only at high strain.
During locomotion, Ib input excites rather than inhibits motoneurons of the receptor-bearing muscles and it also affects the timing of the transitions between the stance and swing phases of locomotion. The switch to autogenetic excitation is a form of positive feedback.
The ascending or afferent
Afferent
Afferent is an anatomical term with the following meanings:*Conveying towards a center, for example the afferent arterioles conveying blood towards the Bowman's capsule in the Kidney. Opposite to Efferent.*Something that so conducts, see Afferent nerve fiber...
pathways to the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
are the dorsal and ventral spinocerebellar tract
Spinocerebellar tract
The spinocerebellar tract is a set of axonal fibers originating in the spinal cord and terminating in the ipsilateral cerebellum. This tract conveys information to the cerebellum about limb and joint position ....
s. They are involved in the cerebellar regulation of movement.
History
Until 1967 it was believed that Golgi tendon organs had a high threshold, only becoming active at high muscle forces. Consequently it was thought that tendon organ input caused "weightlifting failure" through the clasp-knife reflexClasp-knife response
Clasp-knife response refers to a stretch reflex with a rapid decrease in resistance when attempting to flex a joint, usually during a neurological examination. It is one of the characteristic responses of a upper motor neuron lesion...
, which protected the muscle and tendons from excessive force. However, the underlying premise was shown to be incorrect by James Houk and Elwood Henneman in 1967.
External links
- 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