The motor system is the set of
central and
peripheral structures in the nervous system that support
motor functions
Motor control is the regulation of movement in organisms that possess a nervous system. Motor control includes reflexes as well as directed movement.
To control movement, the nervous system must integrate multimodal sensory information (both f ...
, i.e. movement.
Peripheral structures may include
skeletal muscles
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...
and
neural connections with muscle tissues.
Central structures include
cerebral cortex
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...
,
brainstem,
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
,
pyramidal system
The pyramidal tracts include both the corticobulbar tract and the corticospinal tract. These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem (''cor ...
including the
upper motor neurons,
extrapyramidal system
In anatomy, the extrapyramidal system is a part of the motor system network causing involuntary actions. The system is called ''extrapyramidal'' to distinguish it from the tracts of the motor cortex that reach their targets by traveling through t ...
,
cerebellum, and the
lower motor neurons
Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower m ...
in the brainstem and the spinal cord.
Pyramidal motor system
The
pyramidal motor system, also called the pyramidal tract or the corticospinal tract, start in the motor center of the
cerebral cortex
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...
.
[Rizzolatti G, Luppino G (2001) The Cortical Motor System. ''Neuron'' 31: 889-90]
SD
/ref> There are upper and lower motor neuron
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...
s in the corticospinal tract. The motor impulses originate in the giant pyramidal cells or Betz cell
Betz cells (also known as pyramidal cells of Betz) are giant pyramidal cells (neurons) located within the fifth layer of the grey matter in the primary motor cortex. These neurons are the largest in the central nervous system, sometimes reaching ...
s of the motor area; i.e., precentral gyrus of cerebral cortex. These are the upper motor neurons (UMN) of the corticospinal tract. The axon
An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action p ...
s of these cells pass in the depth of the cerebral cortex to the corona radiata
In neuroanatomy, the corona radiata is a white matter sheet that continues inferiorly as the internal capsule and superiorly as the centrum semiovale. This sheet of both ascending and descending axons carries most of the neural traffic from and ...
and then to the internal capsule
The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the ...
, passing through the posterior branch of internal capsule and continuing to descend in the midbrain and the medulla oblongata. In the lower part of the medulla oblongata, 90–95% of these fibers decussate (pass to the opposite side) and descend in the white matter
White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distributi ...
of the lateral funiculus
The most lateral of the bundles of the anterior nerve roots is generally taken as a dividing line that separates the anterolateral system
The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory path ...
of the spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
on the opposite side. The remaining 5–10% pass to the same side. Fibers for the extremities (limb
Limb may refer to:
Science and technology
*Limb (anatomy), an appendage of a human or animal
*Limb, a large or main branch of a tree
*Limb, in astronomy, the curved edge of the apparent disk of a celestial body, e.g. lunar limb
*Limb, in botany, ...
s) pass 100% to the opposite side. The fibers of the corticospinal tract terminate at different levels in the anterior horn of the grey matter
Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distingu ...
of the spinal cord. Here, the lower motor neurons (LMN) of the corticospinal cord are located. Peripheral motor nerves carry the motor impulses from the anterior horn to the voluntary muscles.
Extrapyramidal motor system
The extrapyramidal motor system consists of motor-modulation systems, particularly the basal ganglia
The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus pallidus into an exter ...
and cerebellum. For information, see extrapyramidal system
In anatomy, the extrapyramidal system is a part of the motor system network causing involuntary actions. The system is called ''extrapyramidal'' to distinguish it from the tracts of the motor cortex that reach their targets by traveling through t ...
.
See also
* Motor skill
A motor skill is a function that involves specific movements of the body's muscles to perform a certain task. These tasks could include walking, running, or riding a bike. In order to perform this skill, the body's nervous system, muscles, and br ...
* Motor control
* Motor disorder
Motor disorders are disorders of the nervous system that cause abnormal and involuntary movements. They can result from damage to the motor system.
Motor disorders are defined in the fifth edition of the '' Diagnostic and Statistical Manual of Men ...
References
External links
*
{{DEFAULTSORT:Motor System
Anatomy
Motor control