The central nervous system (CNS) is the part of the nervous system The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous system contains the brain, spinal cord, and retina that coordinates the activity of all parts of the bodies of bilaterian The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back. The bilateralia are a subregnum (a major group) of animals, including the majority of phyla; the most notable exceptions animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish The Radiata are the radially symmetric animals of the Eumetazoa subkingdom. The term Radiata has had various meanings in the history of classification. It has been applied to the echinoderms, although the echinoderms are members of the Bilateria, because they exhibit bilateral symmetry in their developing stages. It contains the majority of the nervous system and consists of the brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary and the 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 spinal cord extends down to the space between the first and second lumbar vertebrae; it does not extend the entire length of the vertebral column. It is around 4, as well as the retina The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These. Together with the peripheral nervous system The Peripheral Nervous System resides or extends outside the central nervous system (CNS), which consists of the brain and spinal cord. The main function of the PNS is to connect the CNS to the limbs and organs. Unlike the central nervous system, the PNS is not protected by bone or by the blood-brain barrier, leaving it exposed to toxins and, it has a fundamental role in the control of behavior Behavior, or behaviour , refers to the actions of an organism or system, usually in relation to its environment, which includes the other organisms or systems around as well as the physical environment. It is the response of the organism or system to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or. The CNS is contained within the dorsal cavity, with the brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary in the cranial cavity The cranial cavity, or intracranial space, is the space formed inside the skull. The brain occupies the cranial cavity, which is lined by the meninges and which contains cerebrospinal fluid to cushion blows and the spinal cord in the spinal cavity The spinal canal is the space in vertebrae through which the spinal cord passes. It is a process of the dorsal human body cavity. This canal is enclosed within the vertebral foramen of the vertebrae. In the intervertebral spaces, the canal is protected by the ligamentum flavum posteriorly and the posterior longitudinal ligament anteriorly. In vertebrates Vertebrates are members of the subphylum Vertebrata, chordates with backbones or spinal columns. About 58,000 species of vertebrates have been described. Vertebrata is the largest subphylum of chordates, and contains many familiar groups of large land animals. Vertebrates comprise cyclostomes, bony fish, sharks and rays, amphibians, reptiles,, the brain is protected by the skull, while the spinal cord is protected by the vertebrae, and both are enclosed in the meninges The meninges is the system of membranes which envelops the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.[1]
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Development
Development of the neural tube Main article: Neuroanatomy Neuroanatomy is the study of the anatomy of nervous tissue and neural structures of the nervous system. In vertebrates the routes that the myriad nerves take from the brain to the rest of the body , and the internal structure of the brain in particular, are both extremely elaborate. As a result, the study of neuroanatomy has developed into aDuring early development of the vertebrate embryo, a longitudinal groove Between the neural folds is a shallow median groove, the neural groove. The groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into a closed tube, the neural tube or canal, the ectodermal wall of which forms the rudiment of the nervous system on the neural plate In human embryology, formation of neural plate is the first step of neurulation. It is created by a flat thickening opposite to the primitive streak of the ectoderm gradually deepens as ridges on either side of the groove (the neural folds In front of the primitive streak two longitudinal ridges, caused by a folding up of the ectoderm, make their appearance, one on either side of the middle line. These are named the neural folds; they commence some little distance behind the anterior end of the embryonic disk, where they are continuous with each other, and from there gradually) become elevated, and ultimately meet, transforming the groove into a closed tube In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into a closed tube, the neural tube or neural, the ectodermal Generally speaking, the ectoderm differentiates to form the nervous system, tooth enamel and the epidermis wall of which forms the rudiment of the nervous system. This tube initially differentiates into three vesicles (pockets): the prosencephalon In the anatomy of the brain of vertebrates, the prosencephalon is the rostral-most (forward-most) portion of the brain. The prosencephalon, the mesencephalon (midbrain), and rhombencephalon (hindbrain) are the three primary portions of the brain during early development of the central nervous system. It controls body temperature, reproductive at the front, the mesencephalon In biological anatomy, the mesencephalon comprises the tectum (or corpora quadrigemini), tegmentum, the ventricular mesocoelia (or "iter"), and the cerebral peduncles, as well as several nuclei and fasciculi. Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (Thalamus, hypothalamus, et, and, between the mesencephalon and the spinal cord, the rhombencephalon The rhombencephalon is a developmental categorization of portions of the central nervous system in vertebrates. (By six weeks in the human embryo) the prosencephalon then divides further into the telencephalon The cerebrum or telencephalon, together with the diencephalon, constitute the forebrain. It is the most anterior or, especially in humans, most superior region of the vertebrate central nervous system. "Telencephalon" refers to the embryonic structure, from which the mature "cerebrum" develops. The dorsal telencephalon, or and diencephalon The diencephalon is the region of the brain that includes the thalamus, metathalamus, hypothalamus, epithalamus, prethalamus or subthalamus and pretectum. The diencephalon and the telencephalon both derive from the prosencephalon (forebrain). The diencephalon is located near the midline of the brain, above the mesencephalon (midbrain); and the rhombencephalon divides into the metencephalon The metencephalon is a developmental categorization of portions of the central nervous system. The metencephalon is composed of the pons and the cerebellum; contains a portion of the fourth ventricle; and the trigeminal nerve , abducens nerve (CN VI), facial nerve (CN VII), and a portion of the vestibulocochlear nerve (CN VIII) and myelencephalon The myelencephalon is a developmental categorization of a portion of the central nervous system. The myelencephalon is composed of the medulla oblongata; contains a portion of the fourth ventricle; as well as the glossopharyngeal nerve , vagus nerve (CN X), accessory nerve (CN XI), hypoglossal nerve (CN XII), and a portion of the vestibulocochlear.
As the vertebrate grows, these vesicles differentiate further still. The telencephalon differentiates into, among other things, the striatum The striatum, also known as neostriatum or striate nucleus, is a subcortical part of the forebrain. It is the major input station of the basal ganglia system. In primates (including humans), the striatum is divided by a white matter tract called the internal capsule into two sectors called the caudate nucleus and putamen, the hippocampus The hippocampus is a major component of the brains of humans and other mammals. It belongs to the limbic system and plays important roles in long-term memory and spatial navigation. Like the cerebral cortex, with which it is closely associated, it is a paired structure, with mirror-image halves in the left and right sides of the brain. In humans and the neocortex The neocortex , also called the neopallium ("new mantel") and isocortex ("equal rind"), is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI (with VI being the innermost and I being the outermost). The neocortex is part of the cerebral cortex (along, and its cavity becomes the first and second ventricles The lateral ventricles are part of the ventricular system of the brain. Classified as part of the telencephalon, they are the largest of the ventricles. Diencephalon elaborations include the subthalamus During development the subthalamus is continuous with the hypothalamus, but is separated by white matter fibres mainly from the internal capsule. Caudally, the subthalamus or prethalamus is separated from the thalamus by the zona limitans intrathalamica. Other nuclei of the subthalamus are the zona incerta, thalamic reticular nucleus, and the, hypothalamus The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland, thalamus The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections. Its function includes relaying sensation, special sense and motor signals to the cerebral cortex, along with the regulation of and epithalamus The epithalamus is a dorsal posterior segment of the diencephalon which includes the habenula, the stria medullaris and the pineal body. Its function is the connection between the limbic system to other parts of the brain, and its cavity forms the third ventricle The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid (CSF). The tectum The tectum is a region of the brain, specifically the dorsal part of the mesencephalon (midbrain). This is contrasted with the tegmentum, which refers to the region ventral to the ventricular system. It is responsible for auditory and visual reflexes, pretectum The pretectum, also known as the pretectal area, is a region of neurons found between the thalamus and midbrain. It receives binocular sensory input from retinal ganglion cells of the eyes, and is the region responsible for maintaining the pupillary light reflex, cerebral peduncle and other structures develop out of the mesencephalon, and its cavity grows into the mesencephalic duct (cerebral aqueduct). The metencephalon becomes, among other things, the pons The pons , sometimes pons Varolii (after Costanzo Varolio, a 16th-century Italian anatomist and surgeon) is a structure located on the brain stem. It is superior to (up from) the medulla oblongata, inferior to (down from) the midbrain, and ventral to (in front of) the cerebellum. In humans and other bipeds this means it is above the medulla, below and the cerebellum The cerebellum is a region of the brain that plays an important role in motor control. It is also involved in some cognitive functions such as attention and language, and probably in some emotional functions such as regulating fear and pleasure responses, but it is its function in movement that is most clearly understood. The cerebellum does not, the myelencephalon forms the medulla oblongata The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers and deals with autonomic functions, such as breathing, heart rate and blood pressure, and their cavities develop into the fourth ventricle.
Brain regions of a 4 week old human embryoEvolution
Main article: Brain 1. Brain; 2. Central nervous system; 3. Spinal cord.Planarians, members of the phylum Platyhelminthes (flatworms), have the simplest, clearly defined delineation of a nervous system into a central nervous system (CNS) and a peripheral nervous system (PNS).[2] [3] Their primitive brain, consisting of two fused anterior ganglia, and longitudinal nerve cords form the CNS; the laterally projecting nerves form the 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.[4] Like planarians, vertebrates have a distinct CNS and PNS, though more complex than those of planarians.
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 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 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 endocasts.
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 known as the neocortex.[5] 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 and sulci - found in the neocortex of most placental mammals (eutherians).[6] 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.[5] 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.[5]
See also: Encephalization, Archicortex
Diseases of the central nervous system
There are many central nervous system diseases, including infections of the central nervous system such as encephalitis and poliomyelitis, neurodegenerative diseases such as Alzheimer's disease and amyotrophic lateral sclerosis, autoimmune and inflammatory diseases such as multiple sclerosis or acute disseminated encephalomyelitis, and genetic disorders such as Krabbe's disease, Huntington's disease, or adrenoleukodystrophy. Lastly, cancers of the central nervous system can cause severe illness and, when malignant, can have very high mortality rates.
See also
- Glossary of anatomical terminology, definitions and abbreviations
- Central nervous system disease
- Neural development
- Neuroradiology
References
- ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. pp. 132–144. ISBN 0-13-981176-1.
- ^ Hickman, Jr., Cleveland P.; Larry S. Roberts, Susan L. Keen, Allan Larson, Helen L'Anson, David J. Eisenhour (2008). Integrated Princinples of Zoology: Fourteenth Edition. New York, NY, USA: McGraw-Hill Higher Education. pp. 733. ISBN 978-0-07-297004-3.
- ^ Campbell, Neil A.; Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson (2008). Biology: Eighth Edition. San Francisco, CA, USA: Pearson / Benjamin Cummings. pp. 1065. ISBN 978-0-8053-6844-4.
- ^ Katsuhiko Mineta, et al. (2003). "Origin and evolutionary process of the CNS elucidated by comparative genomics analysis of planarian ESTs" (pdf). PNAS 100 (13): 7666–7671. doi:10.1073/pnas.1332513100. PMID 12802012. PMC 164645. http://www.pnas.org/content/100/13/7666.full.pdf+html?sid=b2a914e7-5647-4ee2-835c-bc54c4927a98.
- ^ a b c Bear, Mark F.; Barry W. Connors, Michael A. Paradiso (2007). Neuroscience: Exploring the Brain: Third Edition. Philadelphia, PA, USA: Lippincott Williams & Wilkins. pp. 196–199. ISBN 978-0-7817-6003-4. http://books.google.com/books?id=75NgwLzueikC&printsec=frontcover&dq=neuroscience+exploring+the+brain.
- ^ Kent, George C.; Robert K. Carr (2001). Comparative Anatomy of the Vertebrates: Ninth Edition. New York, NY, USA: McGraw-Hill Higher Education. pp. 408. ISBN 0-07-303869-5.
External links
| Wikimedia Commons has media related to: Central nervous system |
- Sylvius: 400+ structure neuroanatomical visual glossary
- High-Resolution Cytoarchitectural Primate Brain Atlases
- Human Brains: A Learning Tool.
- Explaining the human nervous system.
- Nervous System - Back Pain - Anatomy (info on nerve pairs).
- Textbook in Medical Physiology And Pathophysiology, many links
- Brain and Cranial Nerves, Anatomy and Physiology Lecture, Northland Community College
- Latest Research on the Brain and Central Nervous System From ScienceDaily
- The Department of Neuroscience at Wikiversity
- Overview of the Central Nervous System, Neuroscience Online (electronic neuroscience textbook by UT Houston Medical School)
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Categories: Neurology | Nervous system | Central nervous system
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Thu, 22 Jul 2010 18:44:18 GMT+00:00
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