Grey matter is a major component of the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
, consisting of
neuron
A neuron, neurone, or nerve cell is an membrane potential#Cell excitability, electrically excitable cell (biology), cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous ...
al
cell bodies,
neuropil
Neuropil (or "neuropile") is any area in the nervous system composed of mostly unmyelinated axons, dendrites and glial cell processes that forms a synaptically dense region containing a relatively low number of cell bodies. The most prevalent a ...
(
dendrite
Dendrites (from Greek δένδρον ''déndron'', "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the ...
s and unmyelinated
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 ...
s),
glial cells
Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form mye ...
(
astrocyte
Astrocytes (from Ancient Greek , , "star" + , , "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of e ...
s and
oligodendrocyte
Oligodendrocytes (), or oligodendroglia, are a type of neuroglia whose main functions are to provide support and insulation to axons in the central nervous system of jawed vertebrates, equivalent to the function performed by Schwann cells in th ...
s),
synapse
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses fr ...
s, and
capillaries
A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...
. Grey matter is distinguished from
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 ...
in that it contains numerous cell bodies and relatively few myelinated axons, while white matter contains relatively few cell bodies and is composed chiefly of long-range myelinated axons.
The colour difference arises mainly from the whiteness of
myelin
Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be l ...
. In living tissue, grey matter actually has a very light grey colour with yellowish or pinkish hues, which come from capillary blood vessels and neuronal cell bodies.
Structure
Grey matter refers to unmyelinated
neuron
A neuron, neurone, or nerve cell is an membrane potential#Cell excitability, electrically excitable cell (biology), cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous ...
s and other cells of the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
. It is present in the
brain
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...
,
brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is ...
and
cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cere ...
, and present throughout 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 spin ...
.
Grey matter is distributed at the surface of the
cerebral hemisphere
The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
s (
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% consisting o ...
) and of the cerebellum (
cerebellar cortex), as well as in the depths of the cerebrum (the
thalamus
The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all direction ...
;
hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus ...
;
subthalamus
The subthalamus or prethalamus is a part of the diencephalon. Its most prominent structure is the subthalamic nucleus. The subthalamus connects to the globus pallidus, a basal nucleus of the telencephalon.
Structure
The subthalamus is locate ...
,
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 extern ...
–
putamen,
globus pallidus
The globus pallidus (GP), also known as paleostriatum or dorsal pallidum, is a subcortical structure of the brain. It consists of two adjacent segments, one external, known in rodents simply as the globus pallidus, and one internal, known in rode ...
and
nucleus accumbens
The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hypot ...
; as well as the
septal nuclei
The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum.
The septal nuclei are loc ...
), cerebellum (deep cerebellar nuclei – the
dentate nuclei,
globose nucleus,
emboliform nucleus, and
fastigial nucleus), and
brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is ...
(the
substantia nigra
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra a ...
,
red nucleus,
olivary nuclei, and
cranial nerve nuclei
A cranial nerve nucleus is a collection of neurons ( gray matter) in the brain stem that is associated with one or more of the cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Les ...
).
Grey matter in the spinal cord is known as the
grey column which travels down the spinal cord distributed in three grey columns that are presented in an "H" shape. The forward-facing column is the
anterior grey column, the rear-facing one is the
posterior grey column
The posterior grey column (posterior cornu, dorsal horn, spinal dorsal horn, posterior horn, sensory horn) of the spinal cord is one of the three grey columns of the spinal cord. It receives several types of sensory information from the body, i ...
and the interlinking one is the
lateral grey column. The grey matter on the left and right side is connected by the
grey commissure. The grey matter in the spinal cord consists of
interneuron
Interneurons (also called internuncial neurons, relay neurons, association neurons, connector neurons, intermediate neurons or local circuit neurons) are neurons that connect two brain regions, i.e. not direct motor neurons or sensory neurons. ...
s, as well as the
cell bodies of
projection neurons
Projection, projections or projective may refer to:
Physics
* Projection (physics), the action/process of light, heat, or sound reflecting from a surface to another in a different direction
* The display of images by a projector
Optics, graphic ...
.
File:Cervical_vertebra_english.png, Cross-section of a spinal vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...
with the spinal cord in the centre (and grey matter labelled).
File:Medulla spinalis - Section - English.svg, Cross-section of 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 spin ...
with the grey matter labelled.
Grey matter undergoes development and growth throughout childhood and adolescence. Recent studies using cross-sectional neuroimaging have shown that by around the age of 8 the volume of grey matter begins to decrease.
However, the density of grey matter appears to increase as a child develops into early adulthood.
Males tend to exhibit grey matter of increased volume but lower density than that of females.
Function
Grey matter contains most of the brain's neuronal cell bodies. The grey matter includes regions of the brain involved in muscle control, and sensory perception such as seeing and hearing, memory, emotions, speech, decision-making, and self-control.
The grey matter in 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 spin ...
is split into three grey columns:
* The
anterior grey column contains
motor neuron
A motor neuron (or motoneuron or efferent neuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly ...
s. These
synapse
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses fr ...
with interneurons and 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 ...
s of cells that have travelled down the
pyramidal tract. These cells are responsible for the movement of muscles.
* The
posterior grey column
The posterior grey column (posterior cornu, dorsal horn, spinal dorsal horn, posterior horn, sensory horn) of the spinal cord is one of the three grey columns of the spinal cord. It receives several types of sensory information from the body, i ...
contains the points where
sensory neuron
Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The ...
s synapse. These receive sensory information from the body, including
fine touch,
proprioception
Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense".
Proprioception is mediated by proprioceptors, mechanosensory neurons ...
, and
vibration
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, suc ...
. This information is sent from receptors of the skin, bones, and joints through sensory neurons whose cell bodies lie in the dorsal root ganglion. This information is then transmitted in axons up the spinal cord in spinal tracts, including the
dorsal column-medial lemniscus tract and the
spinothalamic tract
The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory ...
.
* The
lateral grey column is the third column of the spinal cord.
The grey matter of the spinal cord can be divided into different layers, called
Rexed laminae. These describe, in general, the purpose of the cells within the grey matter of the spinal cord at a particular location.
File:Anatomy and physiology of animals A reflex arc.jpg, Interneuron
Interneurons (also called internuncial neurons, relay neurons, association neurons, connector neurons, intermediate neurons or local circuit neurons) are neurons that connect two brain regions, i.e. not direct motor neurons or sensory neurons. ...
s present in the grey matter of the spinal cord
File:Medulla spinalis - Substantia grisea - English.svg, Rexed laminae groups the grey matter in the spinal cord according to its function.
Clinical significance
High
alcohol consumption has been correlated with significant reductions in grey matter volume. Short-term
cannabis
''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: '' Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternativel ...
use (30 days) is not correlated with changes in
white
White is the lightness, lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully diffuse reflection, reflect and scattering, scatter all the ...
or grey matter. However, several cross-sectional studies have shown that repeated long-term cannabis use is associated with smaller grey matter volumes in the
hippocampus
The hippocampus (via Latin from Greek , ' seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, ...
,
amygdala
The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex v ...
, medial
temporal cortex
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The temporal lobe is involved in p ...
, and
prefrontal cortex
In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA ...
, with increased grey matter volume in the cerebellum. Long-term cannabis use is also associated with alterations in white matter integrity in an age-dependent manner, with heavy cannabis use during adolescence and early adulthood associated with the greatest amount of change.
Meditation has been shown to change grey matter structure.
Habitual playing of action video games has been reported to promote a reduction of grey matter in the hippocampus while 3D platformer games have been reported to increase grey matter in the hippocampus.
Women and men with equivalent IQ scores have differing proportions of grey to white matter in cortical brain regions associated with intelligence.
Pregnancy renders substantial changes in brain structure, primarily reductions in grey matter volume in regions subserving social cognition. The grey matter reductions endured for at least 2 years post-pregnancy. The profile of brain changes is comparable to that taking place during adolescence, a hormonally similar transitional period of life.
History
Etymology
In the current edition
[Federative Committee on Anatomical Terminology (FCAT) (1998). ''Terminologia Anatomica''. Stuttgart: Thieme] of the official Latin nomenclature, ''
Terminologia Anatomica
''Terminologia Anatomica'' is the international standard for human anatomical terminology. It is developed by the Federative International Programme on Anatomical Terminology, a program of the International Federation of Associations of Anatomis ...
'', ''substantia grisea'' is used for English ''grey matter''. The adjective ''grisea'' for ''grey'' is however not attested in
classical Latin
Classical Latin is the form of Literary Latin recognized as a literary standard by writers of the late Roman Republic and early Roman Empire. It was used from 75 BC to the 3rd century AD, when it developed into Late Latin. In some later pe ...
.
The adjective ''grisea'' is derived from the
French
French (french: français(e), link=no) may refer to:
* Something of, from, or related to France
** French language, which originated in France, and its various dialects and accents
** French people, a nation and ethnic group identified with Franc ...
word for grey, ''gris''.
Alternative designations like ''substantia cana''
and ''substantia cinerea''
are being used alternatively. The adjective ''cana'', attested in classical Latin,
can mean ''grey'',
or ''greyish white''.
The classical Latin ''cinerea'' means ''ash-coloured''.
Additional images
Image:Human brain right dissected lateral view description.JPG , Human brain right dissected lateral view
Image:Gray678.png, Schematic representation of the chief ganglionic categories (I to V).
See also
*
Grey matter heterotopia
References
External links
*
{{DEFAULTSORT:Grey Matter
Neuroanatomy
Central nervous system