Golgi tendon reflex
Encyclopedia
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 stretch reflex
. Though muscle tension
is increasing during the contraction, alpha motor neuron
s in the spinal cord supplying the muscle are inhibited. However, antagonistic muscles
are activated.
from the Golgi tendon organ fires into the central nervous system
. Second, the motor neuron from the spinal cord is inhibited via an IPSP
and muscle relaxes. Recently, however, this information has proven to be inaccurate since the GTO cannot create sufficient inhibition (Pratt et al., 1995).
operates as a feedback
mechanism to control muscle length by causing muscle contraction. In contrast, the tendon reflex operates as a feedback mechanism to control muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might be torn. Although the tendon reflex is less sensitive than the stretch reflex, it can override the stretch reflex when tension is great, making you drop a very heavy weight, for example. Like the stretch reflex, the tendon reflex is ipsilateral. The sensory receptors for this reflex are called tendon Golgi receptors, which lie within a tendon near its junction with a muscle. In contrast to muscle spindles, which are sensitive to changes in muscle length, tendon organs detect and respond to changes in muscle tension that are caused by passive stretch or muscular contraction.
is a stretch reflex
with a rapid decrease in resistance when attempting to flex a joint. However, it is actually thought to be caused by the tendon reflex of the antagonistic muscle of that joint, which gets extended. It is one of the characteristic responses of an upper motor neuron lesion.
Reflex arc
A reflex arc is a neural pathway that controls an action reflex. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord...
of the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
. In a Golgi tendon reflex, 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...
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 stretch reflex
Stretch reflex
The stretch reflex is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length....
. Though muscle tension
Muscle tone
In physiology, medicine, and anatomy, muscle tone is the continuous and passive partial contraction of the muscles, or the muscle’s resistance to passive stretch during resting state. It helps maintain posture, and it declines during REM sleep.-Purpose:Unconscious nerve impulses maintain the...
is increasing during the contraction, alpha motor neuron
Alpha motor neuron
Alpha motor neurons are large lower motor neurons of the brainstem and spinal cord. They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction...
s in the spinal cord supplying the muscle are inhibited. However, antagonistic muscles
Antagonist (muscle)
Most muscles work in pairs, and when a muscle works it needs to have an agonist and an antagonist, unless the muscle's natural state is opposite to that which is produced by the muscle, example Sphincter ani externus muscle....
are activated.
Function
The Golgi tendon reflex protects the skeletal muscle from excessively heavy loads by causing the muscle to relax and drop the load. First, as a load is placed on the muscle, the afferent neuronAfferent nerve
In the nervous system, afferent neurons , carry nerve impulses from receptors or sense organs towards the central nervous system. This term can also be used to describe relative connections between structures. Afferent neurons communicate with specialized interneurons...
from the Golgi tendon organ fires into the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. Second, the motor neuron from the spinal cord is inhibited via an IPSP
Inhibitory postsynaptic potential
An inhibitory postsynaptic potential is a synaptic potential that decreases the chance that a future action potential will occur in a postsynaptic neuron or α-motoneuron...
and muscle relaxes. Recently, however, this information has proven to be inaccurate since the GTO cannot create sufficient inhibition (Pratt et al., 1995).
Contrast to stretch reflex
The stretch reflexStretch reflex
The stretch reflex is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length....
operates as a 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...
mechanism to control muscle length by causing muscle contraction. In contrast, the tendon reflex operates as a feedback mechanism to control muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might be torn. Although the tendon reflex is less sensitive than the stretch reflex, it can override the stretch reflex when tension is great, making you drop a very heavy weight, for example. Like the stretch reflex, the tendon reflex is ipsilateral. The sensory receptors for this reflex are called tendon Golgi receptors, which lie within a tendon near its junction with a muscle. In contrast to muscle spindles, which are sensitive to changes in muscle length, tendon organs detect and respond to changes in muscle tension that are caused by passive stretch or muscular contraction.
Steps
A tendon reflex operates as follows:- As the tension applied to a tendon increases, the Golgi tendon organ (sensory receptor) is stimulated (depolarized to thresholdThreshold potentialThe threshold potential is the membrane potential to which a membrane must be depolarized to initiate an action potential.It often can be between −40 and -55 mV, but it can vary based upon several factors...
). - Nerve impulses (action potentialAction potentialIn 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...
s) arise and propagate into the spinal cord along a sensory neuron. - Within the spinal cord (integrating center), the sensory neuron activates an inhibitory interneuronInterneuronAn interneuron is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways...
that makes a synapse with a motor neuron. - The inhibitory neurotransmitterNeurotransmitterNeurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
inhibits (hyperpolarizes) the motor neuron, which then generates fewer nerve impulses. - The muscle relaxes and relieves excess tension.
Pathology
The clasp-knife responseClasp-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...
is a stretch reflex
Stretch reflex
The stretch reflex is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length....
with a rapid decrease in resistance when attempting to flex a joint. However, it is actually thought to be caused by the tendon reflex of the antagonistic muscle of that joint, which gets extended. It is one of the characteristic responses of an upper motor neuron lesion.
See also
- Reflex actionReflex actionA reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
- Reflex arcReflex arcA reflex arc is a neural pathway that controls an action reflex. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord...
- Muscle spindleMuscle spindleMuscle spindles are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts...
- H-reflexH-reflexThe H-reflex is a reflectory reaction of muscles after electrical stimulation of sensory fibers in their innervating nerves...
- Motor controlMotor controlMotor control are information processing related activities carried out by the central nervous system that organize the musculoskeletal system to create coordinated movements and skilled actions...
- Stretch ReflexStretch reflexThe stretch reflex is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length....