The central nervous system (CNS) is the part of the
nervous system consisting primarily of the
brain
A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
and
spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all parts of the bodies of
bilaterally symmetric and triploblastic animals—that is, all multicellular animals except
sponge
Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throu ...
s and
diploblasts. It is a structure composed of
nervous tissue
Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the bra ...
positioned along the
rostral (nose end) to caudal (tail end) axis of the body and may have an enlarged section at the rostral end which is a brain. Only
arthropods,
cephalopods
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, a ...
and
vertebrates have a true brain (precursor structures exist in
onychophorans,
gastropods and
lancelets
The lancelets ( or ), also known as amphioxi (singular: amphioxus ), consist of some 30 to 35 species of "fish-like" benthic filter feeding chordates in the order Amphioxiformes. They are the modern representatives of the subphylum Cephalochorda ...
).
The rest of this article exclusively discusses the vertebrate central nervous system, which is radically distinct from all other animals.
Overview
In
vertebrates, the brain and spinal cord are both enclosed in the
meninges.
The meninges provide
a barrier to chemicals dissolved in the blood, protecting the brain from most
neurotoxins commonly found in food. Within the meninges the brain and spinal cord are bathed in
cerebral spinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...
which replaces the
body fluid found outside the cells of all
bilateral animals
The Bilateria or bilaterians are animals with bilateral symmetry as an embryo, i.e. having a left and a right side that are mirror images of each other. This also means they have a head and a tail (anterior-posterior axis) as well as a belly and ...
.
In vertebrates, the CNS is contained within the
dorsal body cavity
The dorsal body cavity is located along the dorsal (posterior) surface of the human body, where it is subdivided into the cranial cavity housing the brain and the spinal cavity housing the spinal cord. The two cavities are continuous with one anot ...
, while the brain is housed in the
cranial cavity within the
skull. The spinal cord is housed in the
spinal canal within the
vertebrae.
Within the CNS, the interneuronal space is filled with a large amount of supporting non-nervous cells called neuroglia or
glia from the Greek for "glue".
In vertebrates, the CNS also includes the
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
and the
optic nerve (
cranial nerve II),
as well as the
olfactory nerves
The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell.
The afferent nerve fibers of the olfactory receptor neurons tr ...
and
olfactory epithelium.
As parts of the CNS, they connect directly to brain neurons without intermediate
ganglia. The
olfactory epithelium is the only central nervous tissue outside the meninges in direct contact with the environment, which opens up a pathway for
therapeutic agents which cannot otherwise cross the meninges barrier.
Structure
The CNS consists of two major structures: the
brain
A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
and
spinal cord. The brain is encased in the skull, and protected by the cranium.
The spinal cord is continuous with the brain and lies
caudally to the brain.
It is protected by the
vertebrae.
The spinal cord reaches from the base of the skull, and continues through
or starting below
the
foramen magnum,
and terminates roughly level with the first or second
lumbar vertebra
The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse ...
,
occupying the upper sections of the
vertebral canal
The spinal canal (or vertebral canal or spinal cavity) is the canal that contains the spinal cord within the vertebral column. The spinal canal is formed by the vertebrae through which the spinal cord passes. It is a process of the dorsal body ...
.
White and gray matter
Microscopically, there are differences between the neurons and tissue of the CNS and the
peripheral nervous system
The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brai ...
(PNS). The CNS is composed of
white and
gray matter.
This can also be seen macroscopically on brain tissue. The white matter consists of
axons and
oligodendrocytes, while the gray matter consists of
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 and unmyelinated fibers. Both tissues include a number of
glial cells (although the white matter contains more), which are often referred to as supporting cells of the CNS. Different forms of glial cells have different functions, some acting almost as scaffolding for
neuroblasts to climb during
neurogenesis such as
bergmann glia, while others such as
microglia are a specialized form of
macrophage, involved in the
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
of the brain as well as the clearance of various
metabolites from the
brain tissue.
Astrocytes may be involved with both clearance of metabolites as well as transport of fuel and various beneficial substances to neurons from the
capillaries of the brain. Upon CNS injury astrocytes will proliferate, causing
gliosis
Gliosis is a nonspecific reactive change of glial cells in response to damage to the central nervous system (CNS). In most cases, gliosis involves the proliferation or hypertrophy of several different types of glial cells, including astrocyte ...
, a form of neuronal scar tissue, lacking in functional neurons.
The brain (
cerebrum
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. ...
as well as
midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness), and temperature regulation. The name comes from the Greek ''mesos'', ...
and
hindbrain) consists of a
cortex, composed of neuron-bodies constituting gray matter, while internally there is more white matter that form
tract
Tract may refer to:
Geography and real estate
* Housing tract, an area of land that is subdivided into smaller individual lots
* Land lot or tract, a section of land
* Census tract, a geographic region defined for the purpose of taking a census
W ...
s and
commissures. Apart from cortical gray matter there is also
subcortical gray matter
In neuroanatomy, a nucleus (plural form: nuclei) is a cluster of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem. The neurons in one nucleus usually have roughly similar connections and functions. N ...
making up a large number of different
nuclei.
Spinal cord
From and to the spinal cord are projections of the peripheral nervous system in the form of
spinal nerves (sometimes segmental nerves
). The nerves connect the spinal cord to skin, joints, muscles etc. and allow for the transmission of
efferent motor as well as
afferent sensory signals and stimuli.
This allows for voluntary and involuntary motions of muscles, as well as the perception of senses.
All in all 31 spinal nerves project from the brain stem,
some forming plexa as they branch out, such as the
brachial plexa,
sacral plexa etc.
Each spinal nerve will carry both sensory and motor signals, but the nerves synapse at different regions of the spinal cord, either from the periphery to sensory relay neurons that relay the information to the CNS or from the CNS to motor neurons, which relay the information out.
The spinal cord relays information up to the brain through spinal tracts through the final common pathway
to 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 direct ...
and ultimately to the cortex.
File:1615 Locations Spinal Fiber Tracts.jpg, Schematic image showing the locations of a few tracts of the spinal cord.
File:1507 Short and Long Reflexes.jpg, Reflexes may also occur without engaging more than one neuron of the CNS as in the below example of a short reflex.
Cranial nerves
Apart from the spinal cord, there are also peripheral nerves of the PNS that synapse through intermediaries or
ganglia directly on the CNS. These 12 nerves exist in the head and neck region and are called
cranial nerves. Cranial nerves bring information to the CNS to and from the face, as well as to certain muscles (such as the
trapezius muscle, which is innervated by
accessory nerve
The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerv ...
s
as well as certain
cervical spinal nerves).
Two pairs of cranial nerves; the
olfactory nerves and the
optic nerves
are often considered structures of the CNS. This is because they do not synapse first on peripheral ganglia, but directly on CNS neurons. The olfactory epithelium is significant in that it consists of CNS tissue expressed in direct contact to the environment, allowing for administration of certain pharmaceuticals and drugs.
Brain
At the anterior end of the spinal cord lies the brain.
The brain makes up the largest portion of the CNS. It is often the main structure referred to when speaking of the nervous system in general. The brain is the major functional unit of the CNS. While the spinal cord has certain processing ability such as that of
spinal locomotion
Spinal locomotion results from intricate dynamic interactions between a central program in lower thoracolumbar spine and proprioceptive feedback from body in the absence of central control by brain as in complete spinal cord injury (SCI). Foll ...
and can process
reflexes, the brain is the major processing unit of the nervous system.
Brainstem
The brainstem consists of the
medulla, the
pons and the
midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness), and temperature regulation. The name comes from the Greek ''mesos'', ...
. The medulla can be referred to as an extension of the spinal cord, which both have similar organization and functional properties.
The tracts passing from the spinal cord to the brain pass through here.
Regulatory functions of the medulla nuclei include control of
blood pressure and
breathing. Other nuclei are involved in
balance,
taste,
hearing, and control of muscles of the
face and
neck.
The next structure rostral to the medulla is the pons, which lies on the ventral anterior side of the brainstem. Nuclei in the pons include
pontine nuclei which work with the
cerebellum and transmit information between the cerebellum and 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% consisting o ...
.
In the dorsal posterior pons lie nuclei that are involved in the functions of breathing, sleep, and taste.
The midbrain, or mesencephalon, is situated above and rostral to the pons. It includes nuclei linking distinct parts of the motor system, including the cerebellum, the
basal ganglia and both
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 hemisphere ...
s, among others. Additionally, parts of the visual and auditory systems are located in the midbrain, including control of automatic eye movements.
The brainstem at large provides entry and exit to the brain for a number of pathways for motor and autonomic control of the face and neck through cranial nerves,
Autonomic control of the organs is mediated by the
tenth cranial nerve.
A large portion of the brainstem is involved in such autonomic control of the body. Such functions may engage the
heart
The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
,
blood vessels, and
pupils, among others.
The brainstem also holds the
reticular formation, a group of nuclei involved in both
arousal and
alertness.
Cerebellum
The cerebellum lies behind the pons. The cerebellum is composed of several dividing fissures and lobes. Its function includes the control of posture and the coordination of movements of parts of the body, including the eyes and head, as well as the limbs. Further, it is involved in motion that has been learned and perfected through practice, and it will adapt to new learned movements.
Despite its previous classification as a motor structure, the cerebellum also displays connections to areas of the cerebral cortex involved in language and
cognition. These connections have been shown by the use of
medical imaging techniques, such as
functional MRI and
Positron emission tomography.
The body of the cerebellum holds more neurons than any other structure of the brain, including that of the larger
cerebrum
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. ...
, but is also more extensively understood than other structures of the brain, as it includes fewer types of different neurons.
It handles and processes sensory stimuli, motor information, as well as balance information from the
vestibular organ.
Diencephalon
The two structures of the diencephalon worth noting are the thalamus and the hypothalamus. The thalamus acts as a linkage between incoming pathways from the peripheral nervous system as well as the optical nerve (though it does not receive input from the olfactory nerve) to the cerebral hemispheres. Previously it was considered only a "relay station", but it is engaged in the sorting of information that will reach cerebral hemispheres (
neocortex).
Apart from its function of sorting information from the periphery, the thalamus also connects the cerebellum and basal ganglia with the cerebrum. In common with the aforementioned reticular system the thalamus is involved in wakefullness and consciousness, such as though the
SCN
SCN may stand for:
Science and technology
*Switched circuit network, i.e. the public switched telephone network
* Server change number, a counter variable used in client-server architecture
*System change number, a stamp that defines a committed ...
.
The hypothalamus engages in functions of a number of primitive emotions or feelings such as
hunger,
thirst and
maternal bonding. This is regulated partly through control of secretion of
hormones from the
pituitary gland
In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The h ...
. Additionally the hypothalamus plays a role in
motivation and many other behaviors of the individual.
Cerebrum
The cerebrum of cerebral hemispheres make up the largest visual portion of the human brain. Various structures combine to form the cerebral hemispheres, among others: the cortex, basal ganglia, amygdala and hippocampus. The hemispheres together control a large portion of the functions of the human brain such as emotion, memory, perception and motor functions. Apart from this the cerebral hemispheres stand for the cognitive capabilities of the brain.
Connecting each of the hemispheres is the
corpus callosum as well as several additional commissures.
One of the most important parts of the cerebral hemispheres is the cortex, made up of gray matter covering the surface of the brain. Functionally, the cerebral cortex is involved in planning and carrying out of everyday tasks.
The hippocampus is involved in storage of memories, the amygdala plays a role in perception and communication of emotion, while the basal ganglia play a major role in the coordination of voluntary movement.
Difference from the peripheral nervous system
This differentiates the CNS from the PNS, which consists of neurons, axons, and
Schwann cells. Oligodendrocytes and Schwann cells have similar functions in the CNS and PNS, respectively. Both act to add
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 ...
sheaths to the axons, which acts as a form of insulation allowing for better and faster proliferation of electrical signals along the nerves. Axons in the CNS are often very short, barely a few millimeters, and do not need the same degree of isolation as peripheral nerves. Some peripheral nerves can be over 1 meter in length, such as the nerves to the big toe. To ensure signals move at sufficient speed, myelination is needed.
The way in which the Schwann cells and oligodendrocytes myelinate nerves differ. A Schwann cell usually myelinates a single axon, completely surrounding it. Sometimes, they may myelinate many axons, especially when in areas of short axons.
Oligodendrocytes usually myelinate several axons. They do this by sending out thin projections of their
cell membrane, which envelop and enclose the axon.
Development
During early development of the vertebrate embryo, a longitudinal
groove on the
neural plate gradually deepens and the ridges on either side of the groove (the
neural folds) become elevated, and ultimately meet, transforming the groove into a closed tube called the
neural tube. The formation of the neural tube is called
neurulation. At this stage, the walls of the neural tube contain proliferating
neural stem cells in a region called the
ventricular zone. The neural stem cells, principally
radial glial cells, multiply and generate
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 through the process of
neurogenesis, forming the rudiment of the CNS.
The
neural tube gives rise to both
brain
A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
and
spinal cord. The anterior (or 'rostral') portion of the neural tube initially differentiates into three brain
vesicles
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane
* Synaptic vesicle
; In human embryology
* Vesicle (embryology), bulge-like features o ...
(pockets): the
prosencephalon at the front, the
mesencephalon, and, between the mesencephalon and the spinal cord, the
rhombencephalon. (By six weeks in the human embryo) the prosencephalon then divides further into the
telencephalon
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. ...
and
diencephalon; and the rhombencephalon divides into the
metencephalon and
myelencephalon. The spinal cord is derived from the posterior or 'caudal' portion of the neural tube.
As a vertebrate grows, these vesicles differentiate further still. The telencephalon differentiates into, among other things, the
striatum, 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 syste ...
and the
neocortex, and its cavity becomes the
first and second ventricles. Diencephalon elaborations include the
subthalamus,
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 ...
,
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 direct ...
and
epithalamus, and its cavity forms the
third ventricle. The
tectum,
pretectum,
cerebral peduncle
The cerebral peduncles are the two stalks that attach the cerebrum to the brainstem. They are structures at the front of the midbrain which arise from the ventral pons and contain the large ascending (sensory) and descending (motor) nerve tract ...
and other structures develop out of the mesencephalon, and its cavity grows into the
mesencephalic duct
The cerebral aqueduct (aqueductus mesencephali, mesencephalic duct, sylvian aqueduct or aqueduct of Sylvius) is a conduit for cerebrospinal fluid (CSF) that connects the third ventricle to the fourth ventricle of the ventricular system of the brai ...
(cerebral aqueduct). The metencephalon becomes, among other things, the
pons and the
cerebellum, the myelencephalon forms the
medulla oblongata, and their cavities develop into the
fourth ventricle.
File:EmbryonicBrain.svg, Diagram depicting the main subdivisions of the embryonic vertebrate brain, later forming forebrain, midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness), and temperature regulation. The name comes from the Greek ''mesos'', ...
and hindbrain.
File:Development of the neural tube.png, Development of the neural tube
Evolution
Planaria
Planarians, members of the phylum
Platyhelminthes (flatworms), have the simplest, clearly defined delineation of a nervous system into a CNS and a
PNS.
Their primitive brains, consisting of two fused anterior ganglia, and longitudinal nerve cords form the CNS. Like vertebrates, have a distinct CNS and PNS. The nerves projecting laterally from the CNS form their PNS.
A molecular study found that more than 95% of the 116 genes involved in the nervous system of planarians, which includes genes related to the CNS, also exist in humans.
Arthropoda
In
arthropods, the
ventral nerve cord, the
subesophageal ganglia The suboesophageal ganglion (acronym: SOG; synonym: ''subesophageal ganglion'') of arthropods and in particular insects is part of the arthropod central nervous system (CNS). As indicated by its name, it is located ''below the'' ''oesophagus'', insi ...
and the
supraesophageal ganglia
The supraesophageal ganglion (also "supraoesophageal ganglion", "arthropod brain" or "microbrain") is the first part of the arthropod, especially insect, central nervous system. It receives and processes information from the first, second, and t ...
are usually seen as making up the CNS. Arthropoda, unlike vertebrates, have inhibitory
motor neurons due to their small size.
Chordata
The CNS of
chordates differs from that of other animals in being placed
dorsally in the body, above the gut and
notochord/
spine
Spine or spinal may refer to:
Science Biology
* Vertebral column, also known as the backbone
* Dendritic spine, a small membranous protrusion from a neuron's dendrite
* Thorns, spines, and prickles, needle-like structures in plants
* Spine (zoolo ...
.
[Romer, A.S. (1949): ''The Vertebrate Body.'' W.B. Saunders, Philadelphia. (2nd ed. 1955; 3rd ed. 1962; 4th ed. 1970)] The basic pattern of the CNS is highly conserved throughout the different species of
vertebrates and during evolution. The major trend that can be observed is towards a progressive telencephalisation: the
telencephalon
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. ...
of reptiles is only an appendix to the large
olfactory bulb, while in mammals it makes up most of the volume of the CNS. In the human brain, the telencephalon covers most of the
diencephalon and the entire
mesencephalon. Indeed, the
allometric study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through
cranial endocast
An endocast is the internal cast of a hollow object, often referring to the cranial vault in the study of brain development in humans and other organisms. Endocasts can be artificially made for examining the properties of a hollow, inaccessible sp ...
s.
=Mammals
=
Mammals – which appear in the fossil record after the first fishes, amphibians, and reptiles – are the only vertebrates to possess the evolutionarily recent, outermost part 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% consisting o ...
(main part of the telencephalon excluding olfactory bulb) known as the
neocortex.
This part of the brain is, in mammals, involved in higher thinking and further processing of all senses in the
sensory cortices (processing for smell was previously only done by its bulb while those for non-smell senses were only done by the
tectum).
[Feinberg, T. E., & Mallatt, J. (2013). The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago. Frontiers in psychology, 4, 667. https://doi.org/10.3389/fpsyg.2013.00667] The neocortex of
monotremes (the duck-billed
platypus and several species of
spiny anteaters) and of
marsupials (such as
kangaroos,
koalas,
opossums,
wombats, and
Tasmanian devils) lack the convolutions –
gyri
In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the brain in humans and other ...
and
sulci – found in the neocortex of most
placental mammals (
eutherians).
Within placental mammals, the size and complexity of the neocortex increased over time. The area of the neocortex of mice is only about 1/100 that of monkeys, and that of monkeys is only about 1/10 that of humans.
[ In addition, rats lack convolutions in their neocortex (possibly also because rats are small mammals), whereas cats have a moderate degree of convolutions, and humans have quite extensive convolutions.][ Extreme convolution of the neocortex is found in dolphins, possibly related to their complex echolocation.
]
Clinical significance
Diseases
There are many CNS diseases and conditions, including infections such as encephalitis and poliomyelitis, early-onset neurological disorders including ADHD and autism, seizure disorders such as epilepsy, headache disorders such as migraine, late-onset neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms beco ...
, and essential tremor, autoimmune and inflammatory diseases such as multiple sclerosis and acute disseminated encephalomyelitis, genetic disorders such as Krabbe's disease
Krabbe disease (KD) (also known as globoid cell leukodystrophy or galactosylceramide lipidosis) is a rare and often fatal lysosomal storage disease that results in progressive damage to the nervous system. KD involves dysfunctional metabolism of ...
and Huntington's disease
Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...
, as well as amyotrophic lateral sclerosis and adrenoleukodystrophy
Adrenoleukodystrophy (ALD) is a disease linked to the X chromosome. It is a result of fatty acid buildup caused by peroxisomal fatty acid beta oxidation which results in the accumulation of very long chain fatty acids in tissues throughout the ...
. Lastly, cancers of the central nervous system can cause severe illness and, when malignant, can have very high mortality rates. Symptoms depend on the size, growth rate, location and malignancy of tumors and can include alterations in motor control, hearing loss, headaches and changes in cognitive ability and autonomic functioning.
Specialty professional organizations recommend that neurological imaging of the brain be done only to answer a specific clinical question and not as routine screening.
References
External links
*
High-Resolution Cytoarchitectural Primate Brain Atlases
Explaining the human nervous system
* The Department of Neuroscience at Wikiversity
Wikiversity is a Wikimedia Foundation project that supports learning communities, their learning materials, and resulting activities. It differs from Wikipedia in that it offers tutorials and other materials for the fostering of learning, rather ...
Central nervous system histology
{{DEFAULTSORT:Central Nervous System
Neuroscience