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Human Nervous System Function

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Last Updated: 02 July 2021

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General | Latest Info

The nervous system is a complex collection of nerves and specialized cells know as neurons that transmit signals between different parts of the body. It is essentially the body's electrical wiring. Structurally, nervous system has two components: central nervous system and the peripheral nervous system. According to the National Institutes of Health, central nervous system is made up of the brain, spinal cord and nerves. The peripheral nervous system consists of sensory neurons, ganglia and nerves that connect to one another and to the central nervous system. Functionally, nervous system has two main subdivisions: somatic, or voluntary, component; and autonomic, or involuntary, component. The autonomic nervous system regulates certain body process, such as blood pressure and rate of breathing, that work without conscious effort, according to Merck Manuals. The somatic system consists of nerves that connect the brain and spinal cord with muscles and sensory receptors in the skin.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Diagnosing nervous system conditions

There are a number of tests and procedures to diagnose conditions involving the nervous system. In addition to traditional X - ray, specialized X - ray called fluoroscopy examines the body in motion, such as blood flowing through arteries, according to NIH. Other standard neurological exams include MRI, CT scan, and electroencephalogram, which record the brain's continuous electrical activity. Positron emission tomography is a procedure that measures cell or tissue metabolism and brain activity to detect tumors or diseased tissue or tumors, NIH note. The Spinal tap places a needle into the spinal canal to drain a small amount of cerebral spinal fluid that is tested for infection or other abnormalities, according to NIH.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Diseases of the nervous system

Nervous systems can be attacked by infectious pathogens - bacteria, viruses, fungi or protozoans. Bacterial infections such as tuberculosis or syphilis can colonize nervous tissue as a secondary site of infection in advanced stages of disease. Meninges covering the central nervous system are particularly susceptible to infection, especially when head trauma allows pathogens from other organs access to these delicate tissues, through cerebrospinal fluid. Other disorders in the nervous system include blocks in vascular networks of the brain due to strokes. Strokes can lead to large - scale loss of function, up to and including complete paralysis. Ailments associated with accumulation of improperly folded proteins are debilitating since neurons must be actively used to build more neurons and create circuits within the brain. Many of these ailments are progressive, ie, symptoms become more debilitating with age, and include Alzheimer's disease and Parkinsons disease. For some ailments, there is a clear genetic factor involved, such as in Huntingtons disease and in some forms of ataxia. In many such cases, there is a single protein whose gene is mutated in such a way that large - scale changes to DNA sequence accumulate over successive generations. In most other neurodegenerative diseases, both genetic and environmental factors seem to be involve.


Overview of Nervous System Disorders

Healthcare providers who treat nervous system disorders may have to spend a lot of time working with patients before making a probable diagnosis of a specific condition. Many times, this involves performing numerous tests to eliminate other conditions, so that probable diagnosis can be make. Neurology. The branch of medicine that manages nervous system disorders is called neurology. Medical healthcare providers who treat nervous system disorders are called neurologists. Some neurologists treat acute strokes and cerebral aneurysms using endovascular techniques. Neurological surgery. The branch of medicine that provides surgical intervention for nervous system disorders is called neurosurgery, or neurological surgery. Surgeons who operate as treatment teams for nervous system disorders are called neurological surgeons or neurosurgeons. Neuroradiologists and interventional radiologists. Radiologists specialize in diagnosis of neurological conditions using imaging and in treatment of certain neurologic conditions such as cerebral aneurysms, acute strokes, and vertebral fractures, as well as biopsies of certain tumors. Rehabilitation for neurological disorders. The branch of medicine that provides rehabilitative care for patients with nervous system disorders is called physical medicine and rehabilitation. Healthcare providers who work with patients in the rehabilitation process are called physiatrists.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Study of the nervous system

Study of the Nervous System involves anatomical and physiological techniques that have improved over years in efficiency and caliber. Clearly, gross morphology of the Nervous System requires an eye - level view of the brain and spinal cord. However, to resolve minute components, optical and electron microscopic techniques are needed Light microscopes and, later, electron microscopes have changed our understanding of intricate connections that exist among nerve cells. For example, modern staining procedures make it possible to see selected neurons that are of one type or another or are affected by growth. With better resolution of electron microscopes, fine structures like synaptic cleft between pre - and post - synaptic neurons can be studied in detail. Along with neuroanatomical techniques, number of other methodologies aid neuroscientists in studying function and physiology of the nervous system. Early on, lesion studies in animals provide information about the function of the nervous system, by ablating parts of the nervous system or using neurotoxins to destroy them and documenting effects on behavior or mental processes. Later, more sophisticated microelectrode techniques were introduce, which led to recording of single neurons in animal brains and investigating their physiological functions. Such studies lead to formulating theories about how sensory and motor information are processed in the brain. To study many neurons, electroencephalographic techniques were introduce. These methods are used to study how large ensembles of neurons, representing different parts of the Nervous System, with or without stimulation, function together. In addition, many scanning techniques that visualize the brain in conjunction with methods mentioned above are used to understand details of the structure and function of the brain. These include computerized axial Tomography, which uses X - rays to capture many pictures of the brain and sandwiches them into 3 - D models to study it. The resolution of this method is inferior to magnetic resonance imaging, which is yet another way to capture brain images using large magnets that bobble hydrogen nuclei in the brain. Although the resolution of MRI scans is much better than CAT scans, they do not provide any functional information about the brain. Positron Emission Tomography involves acquisition of physiologic images of the brain based on detection of positrons. Radio - labeled isotopes of certain chemicals, such as analogs of glucose, enter Active nerve cells and emit positrons, which are captured and mapped into scans. Such scans show how the brain and its many modules become active when energized with entering glucose analog. Disadvantages of PET scans include being invasive and rendering poor spatial resolution. The latter is why modern PET machines are coupled with CAT scanners to gain better resolution of functioning brain. Finally, to avoid the invasiveness of PET, functional MRI techniques were develop. Brain images based on fMRI technique visualize brain function by changes in flow of fluids in brain areas that occur over time.


Development of the Nervous System

Emerging nervous system of vertebrates first appear as thickening of ectoderm in dorsal midline. This thickened region, neural plate, arises in response to the inductive influence of underlying notochord and mesoderm, which during the process of gastrulation invaginate from region called Hensen's node or dorsal lip of blastopore and extend forward toward the future head - end of the embryo. Despite considerable effort, mainly in the period between two World Wars, nature of this inductive influence is still poorly understood. In large part, this is because the amounts of tissue available for study are severely limited and because, until relatively recently, our knowledge of gene activation was rudimentary. The availability of modern molecular genetic techniques should make it possible in the near future to identify factors involved in neural induction and to isolate and characterize them. Coincident with induction of neural plate, tissue along its margins is induced to form presumptive neural crest. The Neural crest itself is a transitory structure that is first recognizable as a longitudinal band on the dorsal surface of neural tube. Almost immediately, cells of crest become widely disperse, migrating along predetermined pathways to skin, gut, head, and so forth, where they give rise to a remarkable number of different tissues. The enormous phenotypic diversity of derivatives of neural crest has made it a subject of special interest in recent years. Among other tissues, it is known to give rise to nearly all pigmented cells, much of mesenchyme and skeletal components of the head and face, and certain endocrine glands, as well as to most peripheral sensory neurons, neurons and supporting cells of autonomic ganglia, and Schwann cells of peripheral nerves. From a variety of ingenious experiments in amphibian and chick embryos, it has become clear that precursor cells in neural crest are pluripotent, and the fate of their progeny is largely determined by the environment through which cells migrate and regions in which they finally come to reside. At least some cells can change their phenotype relatively late in life given the right conditions. For example, cultured sympathetic neurons that normally synthesize only neurotransmitter noradrenalin can, in time, begin to synthesize and release acetylcholine.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Neuronal development

Table

Week:12345678
Carnegie stage:1 2 3 45 67 8 910 11 12 1314 1516 1718 1920 21 22 23

In the early stages of development, three iconic layers of tissue develop within the embryo: endoderm, mesoderm, and ectoderm. Nervous systems develop from section of Ectoderm called Neural Plate, which begins to differentiate under the influence of nearby Notochord and paraxial mesoderm around third week. Edges of Neural Plate then elevated to form Neural folds. In a process called neurulation, neural folds curve upward and fuse to form a Neural Tube, which will eventually become CNS. The Neural Plate also form Neural Crest, cells of which will later migrate to different parts of the body and become most of the cells in PNS and ANS. Neurulation begins in the fourth Week of Development. Neural folds fuse first in the cervical region and continue to fuse in both cranial and caudal directions until only the very end of the Tube remains open and connects with the amniotic cavity. These openings are called Neuropores, with an opening at the cranial end of the embryo being rostral neuropore, and opening at the caudal end being caudal neuropore. The Rostral neuropore closes around day 25, and the caudal neuropore closes approximately two days later. The Neural Tube becomes vascularize around the time that Neuropores close. Regions of the Neural Tube begin to thicken, forming brain and spinal cord, and opening within the Tube begin to form ventricles and central spinal canal. During this time in development, certain genes become vital in ensuring accurate structural layout of CNS: Sonic Hedgehog, Pax Genes, bone morphogenic proteins, and transforming growth factor called dorsalin. These components are all influential in appropriate dorsoventral patterning of developing Neural Tube.


Development of the Central Nervous System

The central nervous system develops from longitudinal grooves on the neural plate that form the rudimentary nervous system. The central nervous system consists of the brain and spinal cord. It is part of the nervous system that integrates information that it receives from, and coordinates activity of, all parts of bodies of Bilaterian animalsthat is, all multicellular animals except radially symmetric animals such as sponges and jellyfish. Some classifications of CNS also include retina and cranial nerves. Together with the peripheral nervous system, it has a fundamental role in behavior control. CNS is contained within the dorsal cavity, with the brain in the cranial cavity and the spinal cord in the spinal cavity. In vertebrates, brain is protected by the skull while the spinal cord is protected by vertebrae, and both are enclose in meninges. During early development of the vertebrate embryo, longitudinal groove on the neural plate gradually deepens and ridges on either side of it become elevated and ultimately meet, transforming the groove into a closed tube, ectodermal wall of which forms the rudiment of the nervous system. This tube initially differentiates into three vesicles: prosencephalon at front, mesencephalon, and between mesencephalon and spinal cord, rhombencephalon. At six weeks in human embryo development, prosencephalon divides further into telencephalon and diencephalon and rhombencephalon divides into metencephalon and myelencephalon. As vertebrates grows, these vesicles differentiate further still. Telencephalon differentiates into, among other things, striatum, hippocampus, and neocortex, and its cavity becomes first and second ventricles. Diencephalon elaborations include subthalamus, hypothalamus, thalamus, and epithalamus, and its cavity forms the third ventricle. The tectum, pretectum, cerebral peduncle, and other structures develop out of the mesencephalon, and its cavity grows into a mesencephalic duct. Metencephalon becomes, among other things, pons and cerebellum; myelencephalon form medulla oblongata; and their cavities develop into the fourth ventricle.


Gliogenesis and Myelination

Glial cells have many different types and roles in central and peripheral neural development, though historically described as supportive. These central glia develop from the same neural stem cells as neurons, while peripheral glia are derived from neural crest.S Early in neural development, special type of developmental glia, radial glia, provides a pathway for developing neuron migration out from the proliferating ventricular layer and is involved in subsequent lamination and columnar organization of central nervous system. Types of glia: radial glia, astroglia, oligodendroglia, microglia and Schwann cells. Links: gliogenesis | Schwann cell

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

Neuropores

Cranial NeuroporeCaudal Neuropore
( stage 11 )( stage 12 )

Week 4 to Week 8

Stage 13Stage 14Stage 16Stage 21
scale bar = 1 mm
Week 4Week 5Week 6Week 8

Early Neural Timeline

Carnegie StageEvent
8(about 18 postovulatory days) neural groove and folds are first seen
9three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open.
10(two days later) neural folds begin to fuse near the junction between brain and spinal cord, when neural crest cells are arising mainly from the neural ectoderm
11(about 24 days) the rostral (or cephalic) neuropore closes within a few hours; closure is bidirectional, it takes place from the dorsal and terminal lips and may occur in several areas simultaneously. The two lips, however, behave differently.
12(about 26 days) The caudal neuropore takes a day to close. The level of final closure is approximately at future somitic pair 31 (corresponds to the level of sacral vertebra 2). Secondary neurulation begins, is the differentiation of the caudal part of the neural tube from the caudal eminence (or end-bud) without the intermediate phase of a neural plate.
13(4 weeks) the neural tube is normally completely closed.
* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Nervous System Parts

Early Neural Timeline

Carnegie StageEvent
8(about 18 postovulatory days) neural groove and folds are first seen
9three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open.
10(two days later) neural folds begin to fuse near the junction between brain and spinal cord, when neural crest cells are arising mainly from the neural ectoderm
11(about 24 days) the rostral (or cephalic) neuropore closes within a few hours; closure is bidirectional, it takes place from the dorsal and terminal lips and may occur in several areas simultaneously. The two lips, however, behave differently.
12(about 26 days) The caudal neuropore takes a day to close. The level of final closure is approximately at future somitic pair 31 (corresponds to the level of sacral vertebra 2). Secondary neurulation begins, is the differentiation of the caudal part of the neural tube from the caudal eminence (or end-bud) without the intermediate phase of a neural plate.
13(4 weeks) the neural tube is normally completely closed.

The Central Nervous System is made up of the brain and spinal cord. The Peripheral Nervous System is made up of nerves that branch off from the spinal cord and extend to all parts of the body. The Nervous System transmits signals between the brain and the rest of the body, including internal organs. In this way, nervous systems activities control ability to move, breathe, see, think, and more. 1 basic unit of the Nervous System is the nerve cell, or neuron. The human brain contains about 100 billion neurons. The neuron has a cell body, which includes a cell nucleus, and special extensions called axons and dendrites. Bundles of axons, called nerves, are found throughout the body. Axons and dendrites allow neurons to communicate, even across long distances. Different types of neurons control or perform different activities. For instance, motor neurons transmit messages from the brain to muscles to generate movement. Sensory neurons detect light, sound, odor, taste, pressure, and heat and send messages about those things to the brain. Other parts of the Nervous System control involuntary processes. These include keeping a regular heartbeat, releasing hormones like adrenaline, opening pupils in response to light, and regulating the digestive system. When a neuron sends a message to another neuron, it sends electrical signal down length of its axon. At the end of the axon, electrical signal changes to chemical signal. Axon then releases chemical signals with chemical messengers called neurotransmitters into synapse space between the end of the axon and the tip of dendrite from another neuron. Neurotransmitters move signal through synapse to neighboring dendrite,s which convert chemical signal back into electrical signal. Electrical signals then travel through neurons and go through the same conversion process as they move to neighboring neurons. The Nervous System also includes non - neuron cells, called glia. Glia performs many important functions that keep the Nervous System working properly. For example, glia: helps support and hold neurons in place, Protect neurons, Create insulation called myelin, which helps move nerve impulses, Repair neurons and helps restore neuron function Trim out dead neurons, Regulate neurotransmitters, brain is made up of many networks of communicating neurons and glia. These networks allow different parts of the brain to talk to each other and work together to control body functions, emotions, thinking, behavior, and other activities.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Nervous System Structure

Early Neural Timeline

Carnegie StageEvent
8(about 18 postovulatory days) neural groove and folds are first seen
9three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open.
10(two days later) neural folds begin to fuse near the junction between brain and spinal cord, when neural crest cells are arising mainly from the neural ectoderm
11(about 24 days) the rostral (or cephalic) neuropore closes within a few hours; closure is bidirectional, it takes place from the dorsal and terminal lips and may occur in several areas simultaneously. The two lips, however, behave differently.
12(about 26 days) The caudal neuropore takes a day to close. The level of final closure is approximately at future somitic pair 31 (corresponds to the level of sacral vertebra 2). Secondary neurulation begins, is the differentiation of the caudal part of the neural tube from the caudal eminence (or end-bud) without the intermediate phase of a neural plate.
13(4 weeks) the neural tube is normally completely closed.

Several attempts have been made to estimate the number and distribution of neurons in human CNS. Human CNS has approximately 86 billion neurons, with a roughly equal number of glial cells, and 99. 9% of these neurons are located in the brain. While the cerebral cortex, including white matter, represents ~82% of the mass of CNS, only ~20% of all neurons reside within this structure, with published estimates of the number of neocortical neurons varying by as much as factor of 2. In contrast, cerebellum represents ~10% of the mass of CNS but has ~80% of neurons, most notably granular neurons. An additional 700 million neurons are present in the rest of CNS, including as few as 20 million neurons in the spinal cord. For comparison, there are around 400 - 600 million neurons in the human enteric nervous system, largest part of the peripheral nervous system. Crucially, recent comparative studies suggest that both the numbers of neurons and glia and the ratio of these cell types to one another in the human cerebral cortex and cerebellum likely follow general scaling rules common to non - great ape primates; as human brains are larger than those of other primates, this again suggests positive relationship between neuron number and cognitive capacities. However, while the human brain has more neurons than any extant NHP, several mammalian species possess more neurons in both CNS and cerebral cortex, including the long - fin pilot whale, species of dolphin with more neurons in the neocortex than any mammal studied to date and almost twice as many as humans. Moreover, humans affected by either congenital or acquired conditions where portions of the brain are severely underdeveloped or missing can have normal or near - normal intelligence and cognitive skills, with examples including some severe forms of microcephaly; childhood hemispherectomy; patients born with only one hemisphere; craniopagus malformation, including pair of craniopagus twins that share brain and mind; individuals with almost complete absence of cerebellum; and case of severe hydrocephaly. Nevertheless, how simple change in brain size or neuron and / or glia number could lead to differences in cognitive capabilities is not, at mechanistic level, well understood. Therefore, key to our brains ' unique capacities may not be simply its absolute or relative size, or even its number of neurons and glia, but instead more nuanced components such as increased diversity of neural cell types, molecular changes, and expanded or more complex patterns of neuronal connectivity. One possibility is that increased cognitive abilities emerge following expansion of the human brain because this expansion untethered large portions of association cortices from previously strong constraints imposed by molecular gradients and neuronal activity patterns, thereby allowing new sets of cortico - cortical synaptic projections, re - wiring of ancestral circuits, and development of new behavioral, cognitive, and phenotypic outcomes.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

What Does the Brain Do?

As a species, humans have evolved a complex nervous system and brain over millions of years. Comparisons of our nervous systems with those of other animals, such as chimpanzees, show some similarities. Researchers can also use fossils to study the relationship between brain volume and human behavior over the course of evolutionary history. Homo habilis, for instance, human ancestor living about 2 million years ago show larger brain volume than its own ancestors but far less than modern homo sapiens. The main difference between humans and other animals - in terms of brain development - is that humans have a much more developed frontal cortex. Interestingly, people's unique nervous systems develop over the course of their lifespan in a way that resembles the evolution of nervous systems in animals across vast stretches of time. For example, human nervous system begins developing even before a person is born. It begins as a simple bundle of tissue that forms into a tube and extends along head - to - tail plane becoming spinal cord and brain. 25 days into its development, embryo has distinct spinal cord, as well as hindbrain, midbrain and forebrain. What, exactly, is this nervous system developing and what does it do? The nervous system can be thought of as the body's communication network that consists of all nerve cells. There are many ways in which we can divide the nervous system to understand it more clearly. One common way to do so is by parsing it into the central nervous system and peripheral nervous system. Each of these can be sub - divide, in turn. Lets take a closer, more in - depth look at each. And, dont worry, nervous system is complicated with many parts and many new vocabulary words. It might seem overwhelming at first, but through figures and little study you can get it.


Brain and Nervous System

If the brain is like a central computer that controls all functions of your body, then the Nervous System is like a network that sends messages back and forth from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back and contains threadlike nerves that branch out to every organ and body part. When a message comes into the brain from anywhere in the body, brain tells the body how to react. For example, if you accidentally touch a hot stove, nerves in your skin shoot message of pain to your brain. The brain then sends a message back telling muscles in your hand to pull away. Luckily, this neurological relay race takes a lot less time than it just takes to read about it!

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

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