* If you want to update the article please login/register
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.
|Definition||A network of neurons that sends, receives and modulates neural impulses between different body parts.|
|Divisions||Central nervous system Peripheral nervous system|
|Central nervous system||Brain and spinal cord|
|Peripheral nervous system||Spinal and cranial nerves. Functional divisions: - Somatic nervous system - Autonomic nervous system; sympathetic, parasympathetic and enteric divisions|
Nerves are cylindrical bundles of fibers that start at the brain and central cord and branch out to every other part of the body, according to University of Michigan Medical School. Neurons send signals to other cells through thin fibers called axons, which cause chemicals know as neurotransmitters to be released at junctions called synapses, NIH note. There are over 100 trillion neural connections in the average human brain, though number and location can vary. For example, new study published in January 2018 in the journal Proceedings of National Academy of Sciences found that out of 160 participants study, brains of highly creative people have more connections among three specific regions of the brain than less creative thinkers. You have these three different systems that are all located in different parts of the brain, but they are all co - activate at once, says lead study author Roger Beaty, postdoctoral fellow studying cognitive neuroscience at Harvard University. People who are better able to co - activate them with more - creative responses. The Synapse gives command to the cell and the entire communication process typically takes only a fraction of a millisecond. Signals travel along alpha motor neuron in the spinal cord 268 mph; fastest transmission in the human body, according to Discover magazine. Sensory neurons react to physical stimuli such as light, sound and touch and send feedback to the Central Nervous System about the body's surrounding environment, according to the American Psychological Association. Motor neurons, located in the Central Nervous System or in Peripheral ganglia, transmit signals to activate muscles or glands. Glial cells, derive from the Greek word for glue, are specialized cells that support, protect or nourish nerve cells, according to Oregon Institute of Health and Science University. The brain's connections and thinking ability have grown over thousands of years of evolution. For example, virus bind its genetic code to the genome of four - limbed animals, and the code can still be found in human brains today, according to two papers published in the January 2018 journal Cell. This code packages up genetic information and sends it from nerve cells to other nearby nerve cells, very important process in the brain.
* 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.
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.
The Nervous system is a complex, highly specialized network. It organize, explains, and directs interactions between you and the world around you. The nervous system controls: sight, hearing, taste, smell, and feeling. Voluntary and involuntary functions, such as movement, balance, and coordination. The nervous system also regulates actions of most other body systems, such as blood flow and blood pressure. Ability to think and reason. The nervous system allows you to be conscious and have thoughts, memories, and language. The nervous system is divided into brain and spinal cord and nerve cells that control voluntary and involuntary movements. Symptoms of nervous system problem depend on which area of the nervous system is involved and what is causing the problem. Nervous system problems may occur slowly and cause gradual loss of function. Or they may occur suddenly and cause life - threatening problems. Symptoms may be mild or severe. Some serious conditions, diseases, and injuries that can cause nervous system problems include: blood supply problems. Injuries, especially injuries to the head and spinal cord. Problems that are present at birth. Mental health problems, such as anxiety disorders, depression, or psychosis. Exposure to toxins, such as carbon monoxide, arsenic, or lead. Problems that cause gradual loss of function. Examples include: Parkinson's disease. Multiple sclerosis. Amyotrophic lateral sclerosis. Alzheimer's disease. Huntington's disease. Peripheral neuropathies. Infections. These may occur in the: Brain. The Membrane surrounds the brain and spinal cord. Overuse of or withdrawal from prescription and nonprescription medicines, illegal drugs, or alcohol. Brain tumor. Organ system failure. Examples include: Respiratory failure. Heart failure. Liver failure. Kidney failure. Other conditions. Some examples include: Thyroid dysfunction. High blood sugar or low blood sugar. Electrolyte problems. Nutritional deficiencies, such as vitamin B1 or vitamin B12 deficiency. Guillain - Barre syndrome. Sudden nervous system problems can cause many different symptoms, depending on the area of nervous system involve. Strokes and transient ischemic attacks are common examples of acute problems. You may experience sudden onset of one or more symptoms, such as: numbness, tingling, weakness, or inability to move part or all of one side of your body. Dimness, blurring, double vision, or loss of vision in one or both eyes. Loss of speech, trouble talking, or trouble understanding speech. Sudden, severe headache. Dizziness, unsteadiness, or inability to stand or walk, especially if other symptoms are present. Confusion or change in level of consciousness or behavior. Severe nausea or vomiting. Seizures can also cause sudden changes in consciousness, feeling,s emotion,s or thought.S Abnormal body movements, such as muscle twitching, may or may not be present. How often seizures occur and how severe they are depends on the cause of seizures and the area of the brain involve. For more information, see topic Seizures. Diabetes can cause problems with balance, either as a result of peripheral neuropathy or stroke. Vertigo and Dizziness are problems of balance and coordination.
* 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.
Multiple Sclerosis - Literally, many hardenings, MS is a disease of unknown cause that manifests as multiple hard plaques of degeneration of insulating layer of nerve fibers in the central nervous system. Loss of insulation allows short circuiting of nerve impulses. Depending upon where degeneration occur, patients may suffer paralysis, sensory disturbances or blindness. Cerebrovascular accident - fancy name for stroke. Blood vessels in the brain may burst, causing internal bleeding. Or, clot may arise in the brain blood vessel, or arise elsewhere and travel to get stuck in brain vessel which then deprives brain tissue of oxygen. Depending upon the area of brain involve, patient may suffer paralysis, loss of speech or loss of vision. Transient Ischemic Attack - ischemia was introduced previously in the circulatory diseases module referring to the heart. It literally means not quite enough blood. A short period of insufficient blood supply to the brain can have the same signs and symptoms as stroke, such as weakness in the arm, partial loss of vision, but the problem lasts less than 24 hours. People who get TIAs are at increased risk of having a stroke in the future. Epilepsy - the Greek word for seizure. Convulsions is another term used. Seizures may have many causes and not all seizures are epilepsy. High fevers in young children may trigger seizures which are short in duration, easily controlled and, typically, have no permanent effects Epilepsy is a specific condition which may occur at any age, Seizures are more intense, longer lasting in duration, and recur with some frequency. Conditions may be controlled with medication, or if unresponsive to drugs, may require surgery. Aphasia - Loss of speech. Speech centers are located on the left side of the brain in the majority of people. If someone suffers a stroke, or traumatic brain injury, and it involves leave side of the brain, they may suffer speech impediments that vary over spectrum of problems from difficulty in finding the right word, speaking slowly and with difficulty, or complete loss of speech. Actually, there are two speech centers. The injury described above involves the motor speech area, area of the brain that produces language by integrating thoughts of speech with movements of the larynx, lips and tongue. There is a second speech area, receptive or Sensory area, that enables us to understand speech. Injury to the latter results in fluent speech, but individuals do not understand what they are hearing.
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.
The majority of the nervous system is tissue made up of two classes of cells: neurons and neuroglia. Neurons, also known as nerve cells, communicate within the body by transmitting electrochemical signals. Neurons look quite different from other cells in the body due to many long cellular processes that extend from their central cell body. The cell body is roughly round part of the neuron that contains nucleus, mitochondria, and most of the cellular organelles. Small tree - like structures called dendrites extend from the cell body to pick up stimuli from the environment, other neurons, or sensory receptor cells. Long transmitting processes called axons extend from the cell body to send signals onward to other neurons or effector cells in the body. There are 3 basic classes of neurons: afferent neurons, Efferent neurons, and interneurons. Afferent neurons. Also known as sensory neurons, different neurons transmit sensory signals to the central nervous system from receptors in the body. Efferent neurons. Also known as motor neurons, Efferent neurons transmit signals from the central nervous system to effectors in the body such as muscles and glands. Interneurons. Interneurons form complex networks within the central nervous system to integrate information received from afferent neurons and to direct function of the body through different neurons. Neuroglia, also know as glial cells, act as ahelpera cells of the nervous system. Each neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and insulate neuron. Because neurons are extremely specialized cells that are essential to body function and almost never reproduce, neuroglia are vital to maintaining a functional nervous system.
Tissues of CNS have extra protection in that they are not exposed to blood or the immune system in the same way as other tissues. Blood vessels that supply the brain with nutrients and other chemical substances lie on top of pia mater. Capillaries associated with these blood vessels in the brain are less permeable than those in other locations in the body. Capillary endothelial cells form tight junctions that control transfer of blood components to the brain. In addition, cranial capillaries have far fewer fenestra and pinocytotic vesicles than other capillaries. As a result, materials in circulatory system have very limited ability to interact with CNS directly. This phenomenon is referred to as blood - brain barrier. Blood - brain barriers protect cerebrospinal fluid from contamination, and can be quite effective at excluding potential microbial pathogens. As a consequence of these defenses, there are no normal microbiota in cerebrospinal fluid. Blood - brain barriers also inhibit movement of many drugs into brain, particularly compounds that are not lipid soluble. This has profound ramifications for treatments involving infections of CNS, because it is difficult for drugs to cross the blood - brain barrier to interact with pathogens that cause infections. The spinal cord also has protective structures similar to those surrounding the brain. Within the bones of the vertebrae are meninges of dura mater, arachnoid mater, pia mater, and blood - spinal cord barrier that control transfer of blood components from blood vessels associated with the spinal cord. To cause infection in the CNS, pathogens must successfully breach the blood - brain barrier or blood - spinal cord barrier. Various pathogens employ different virulence factors and mechanisms to achieve this, but they can generally be grouped into four categories: intercellular, transcellular, leukocyte facilitate, and nonhematogenous. Intercellular entry involves use of microbial virulence factors, toxins, or inflammation - mediate processes to pass between cells of the blood - brain barrier. In transcellular entry, pathogen passes through cells of the blood - brain barrier using virulence factors that allow it to adhere to and trigger uptake by vacuole - or receptor - mediate mechanisms. Leukocyte - facilitated entry is a Trojan - horse mechanism that occurs when pathogens infect peripheral blood leukocytes to directly enter CNS. Nonhematogenous entry allows pathogens to enter the brain without encountering the blood - brain barrier; it occurs when pathogens travel along either olfactory or trigeminal cranial nerves that lead directly into CNS.
The picture you have in your mind of the nervous system probably includes the brain, nervous tissue contained within the cranium, and spinal cord, extension of nervous tissue within the vertebral column. That suggests it is made of two organsaand you may not even think of the spinal cord as the organabut nervous system is a very complex structure. Within the brain, many different and separate regions are responsible for many different and separate functions. It is as if the nervous system is composed of many organs that all look similar and can only be differentiated using tools such as microscope or electrophysiology. In comparison, it is easy to see that the stomach is different than the esophagus or liver, so you can imagine the digestive system as a collection of specific organs. In 2003, Nobel Prize in Physiology or Medicine was awarded to Paul C. Lauterbur and Sir Peter Mansfield for discoveries related to magnetic resonance imaging. This is a tool to see structures of the body that depend on magnetic fields associated with certain atomic nuclei. The utility of this technique in the nervous system is that fat tissue and water appear as different shades of black and white. Because white matter is fatty and gray matter is not, they can be easily distinguished in MRI images. Try this PhET simulation that demonstrates use of this technology and compare it with other types of imaging technologies. Also, results from MRI session are compared with images obtained from X - ray or computed tomography. How do imaging techniques shown in this game indicate separation of white and gray matter compared with freshly dissected tissue shown earlier?
The nervous system has 3 main functions: sensory, integration, and motor. Sensory. The sensory function of the nervous system involves collecting information from sensory receptors that monitor the bodyas internal and external conditions. These signals are then passed on to the central nervous system for further processing by afferent neurons. Integration. The process of integration is the processing of many sensory signals that are passed into CNS at any given time. These signals are evaluate, compare, used for decision making, discarded or committed to memory as deemed appropriate. Integration takes place in gray matter of the brain and spinal cord and is performed by interneurons. Many interneurons work together to form complex networks that provide this processing power. Motor. Once networks of interneurons in CNS evaluate sensory information and decide on action, they stimulate efferent neurons. Efferent neurons carry signals from gray matter of CNS through nerves of the peripheral nervous system to effector cells. Effector may be smooth, cardiac, or skeletal muscle tissue or glandular tissue. Effector then releases hormones or moves part of the body to respond to stimulus. Unfortunately, of course, our nervous system does always function as it should. Sometimes this is a result of diseases like Alzheimeras and Parkinsonas disease. Do you know that DNA testing can help you discover your genetic risk of acquiring certain health conditions that affect organs of our nervous system? Late - onset Alzheimeras, Parkinsonas disease, macular degeneration - visit our guide to DNA health testing to find out more.
Nervous systems can be divided into two parts, mostly on the basis of functional differences in responses. The somatic nervous system is responsible for conscious perception and voluntary motor responses. Voluntary motor response means contraction of skeletal muscle, but those contractions are not always voluntary in the sense that you have to want to perform them. Some somatic motor responses are reflexes, and often happen without conscious decision to perform them. If your friend jumps out from behind corner and yells aBoo! You will be startled and you might scream or leap back. You did decide to do that, and you may not have wanted to give your friend reason to laugh at your expense, but it is reflex involving skeletal muscle contractions. Other motor responses become automatic as people learn motor skills. The autonomic nervous system is responsible for involuntary control of the body, usually for the sake of homeostasis. Sensory input for autonomic functions can be from sensory structures tuned to external or internal environmental stimuli. Motor output extends to smooth and cardiac muscle as well as glandular tissue. The role of the autonomic system is to regulate organ systems of the body, which usually means to control homeostasis. Sweat glands, for example, are controlled by an autonomic system. When you are hot, sweating helps cool your body down. That is homeostatic mechanism. But when you are nervous, you might start sweating also. That is not homeostatic, it is a physiological response to emotional state. There is another division of nervous system that describes functional responses. The Enteric nervous system is responsible for controlling smooth muscle and glandular tissue in your digestive system. It is a large part of PNS, and is not dependent on CNS. It is sometimes valid, however, to consider the enteric system to be part of the autonomic system because neural structures that make up the enteric system are component of autonomic output that regulate digestion. There are some differences between the two, but for our purposes here there will be a good bit of overlap. See Figure 12. 6 for examples of where these divisions of the nervous system can be find.
Nerves that connect to the spinal cord are spinal nerves. Arrangement of these nerves is much more regular than that of Cranial nerves. All spinal nerves are combined of sensory and motor axons that separate into two nerve roots. Sensory axons enter the spinal cord as dorsal nerve root. Motor fibers, both somatic and autonomic, emerge as ventral nerve root. Dorsal root ganglion for each nerve is enlargement of the spinal nerve. There are 31 spinal nerves, named for the level of spinal cord at which each one emerge. There are eight pairs of cervical nerves designated C1 to C8, twelve thoracic nerves designated T1 to T12, five pairs of lumbar nerves designated L1 to L5, five pairs of sacral nerves designated S1 to S5, and one pair of coccygeal nerves. Nerves are number from superior to inferior positions, and each emerges from the vertebral column through intervertebral foramen at its level. The first Nerve, C1, emerges between the first cervical vertebra and the occipital bone. The second Nerve, C2, emerges between the first and second cervical vertebrae. The same occurs for C3 to C7, but C8 emerges between the seventh cervical vertebra and first thoracic vertebra. For thoracic and lumbar nerves, each one emerges between vertebra that has the same designation and the next vertebra in the column. Sacral nerves emerge from sacral foramina along the length of that unique vertebra. Spinal nerves extend outward from the vertebral column to the enervate periphery. Nerves in the periphery are not straight continuations of spinal nerves, but rather reorganization of axons in those nerves to follow different courses. Axons from different spinal nerves will come together into a systemic nerve. This occurs at four places along the length of the vertebral column, each identified as Nerve plexus, whereas other spinal nerves directly correspond to nerves at their respective levels. In this instance, word plexus is used to describe networks of nerve fibers with no associated cell bodies. Of four nerve plexuses, two are found at cervical level, one at lumbar level, and one at sacral level. The Cervical plexus is composed of axons from spinal nerves C1 through C5 and branches into nerves in the posterior neck and head, as well as the phrenic Nerve, which connects to the diaphragm at the base of the thoracic cavity. The other plexus at cervical level is the brachial plexus. Spinal nerves C4 through T1 reorganize through this plexus to give rise to nerves of arms, as the name brachial suggests. The large nerve from this plexus is the radial nerve from which axillary nerve branches to go to the armpit region. The Radial Nerve continues through the arm and is parallel by the ulnar Nerve and median Nerve.
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.
The forebrain is the largest and most complex part of the brain. It consists of the cerebrum area with all folds and grooves typically seen in pictures of the brain as well as some other structures under it. Cerebrum contains information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: frontal, parietal, temporal, and occipital lobes. Cerebrum has right and left halves, called hemispheres. They are re connected in the middle by a band of nerve fibers that let them communicate. These halves may look like mirror images of each other, but many scientists believe they have different functions: left side is considered logical, analytical, objective side. The right side is thought to be more intuitive, creative, and subjective. So when you re balancing your checkbook, you re using left side. When you re listening to music, you re using right side. It's believed that some people are more right - brain or leave - brain while others are more whole - brain, meaning they use both halves of their brain to the same degree. The outer layer of the cerebrum is called the cortex. Information collected by five senses comes into the brain to cortex. This information is then directed to other parts of the nervous system for further processing. For example, when you touch a hot stove, not only do message go out to move your hand but one also goes to another part of your brain to help you remember not to do that again. In the inner part of the forebrain sits the thalamus, hypothalamus, and pituitary gland: thalamus carries messages from sensory organs like eyes, ears, nose, and fingers to the cortex. The hypothalamus controls pulse, thirst, appetite, sleep patterns, and other processes in our bodies that happen automatically. The Hypothalamus also controls the pituitary gland, which makes hormones that control growth, metabolism, water and mineral balance, sexual maturity, and response to stress.
The Central Nervous System, or CNS for short, is made up of the brain and spinal cord. Cns is a portion of the nervous system that is encase in bone. It is referred to as Central because it is the brain and spinal cord that are primarily responsible for processing sensory informationtouching hot stove or seeing rainbow, for exampleand, sending signals to the peripheral Nervous System for action. It communicates largely by sending electrical signals through individual nerve cells that make up fundamental building blocks of the Nervous System, called neurons. There are approximately 100 billion neurons in the human brain and each has many contacts with other neurons, called synapses. If we were able to magnify the view of individual neurons, we would see that they are cells made from distinct parts. Three main components of neuron are dendrites, soma, and axon. Neurons communicate with one another by receiving information through dendrites, which act as antenna. When dendrites channel this information to the soma, or cell body, it builds up as an electro - chemical signal. This electrical part of the signal, called action potential, shoots down axon, long tail that leads away from soma and toward the next neuron. When people talk about nerves in the Nervous System, it typically refers to bundles of axons that form long neural wires along which electrical signals can travel. Cell - to - cell communication is helped by the fact that the axon is covered by a myelin sheath layer of fatty cells that allow signals to travel very rapidly from neuron to neuron. If we were to zoom in still further, we could take a closer look at synapse, space between neurons. Here, we would see that there is space between neurons, called the synaptic gap. To give you a sense of scale, we can compare the synaptic gap to the thickness of the dime, thinnest of all American coins. You could stack approximately 70 000 synaptic gaps in the thickness of a single coin! As action potential, electrical signal reaches the end of the axon, tiny packets of chemicals, called neurotransmitters, are release. This is chemical part of electro - chemical signal. These neurotransmitters are chemical signals that travel from one neuron to another, enabling them to communicate with one another. There are many different types of neurotransmitters and each has a specialized function. For example, serotonin affects sleep, hunger and mood. Dopamine is associated with attention, learning and pleasure. It is amazing to realize that when you thinkwhen you reach out to grab a glass of water, when you realize that your best friend is happy, when you try to remember the names of parts of the neuronwhat you are experiencing is actually electro - chemical impulses shooting between nerves!
Cns include the brain and spinal cord, while PNS is a network of nerves linking the body to the brain and spinal cord. The nervous system is comprised of two major subdivisions, central nervous system and the peripheral nervous system. CNS includes the brain and spinal cord along with various centers that integrate all sensory and motor information in the body. These centers can be broadly subdivided into lower centers, including the spinal cord and brain stem, that carry out essential body and organ - control functions and higher centers within the brain that control more sophisticated information processing, including our thoughts and perceptions. Further subdivisions of the brain will be discussed in a later section. The nervous system is often divided into components called gray matter and white matter. Gray matter, which is gray in preserved tissue but pink or light brown in living tissue, contains a relatively high proportion of neuron cell bodies. Conversely, white matter is composed mainly of axons and is named because of the color of fatty insulation called myelin that coats many axons. White matter includes all of the nerves of the PNS and much of the interior of the brain and spinal cord. Gray matter is found in clusters of neurons in the brain and spinal cord and in cortical layers that line their surfaces. By convention, cluster of neuron cell bodies in the gray matter of the brain or spinal cord is called nucleus, whereas cluster of neuron cell bodies in the periphery is called ganglion. However, there are a few notable exceptions to this rule, including part of the brain called basal ganglia, which will be discussed later. Pns is a vast network of nerves consisting of bundles of axons that link the body to the brain and spinal cord. Sensory nerves of PNS contain sensory receptors that detect changes in the internal and external environment. This information is sent to CNS via different sensory nerves. Following information processing in CNS, signals are relayed back to the PNS by way of efferent peripheral nerves. Pns is further subdivided into autonomic nervous system and somatic nervous system. The autonomic system has involuntary control of internal organs, blood vessels, and smooth and cardiac muscles. The somatic system has voluntary control of our movements via skeletal muscle. As mentioned, autonomic nervous system acts as a control system and most functions occur without conscious thought. Ans affect heart rate, digestion, respiratory rate, salivation, perspiration, pupil diameter, urination, and sexual arousal. While most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind. Ans is classically divided into two subsystems: parasympathetic nervous system and sympathetic nervous system. Broadly, parasympathetic system is responsible for stimulation of rest - and - digest activities that occur when the body is at rest, including sexual arousal, salivation, lacrimation, urination, digestion, and defecation.
As you might predict, human nervous system is very complex. It has multiple divisions, beginning with its two main parts, Central Nervous System and Peripheral Nervous System, as shown in Figure: CNS includes brain and spinal cord, and PNS consists mainly of nerves, which are bundles of axons from neurons. Nerves of PNS connect CNS to the rest of the body. You can learn much more about CNS by reading the concept of Central Nervous System. Pns is divided into two major parts, called autonomic and somatic Nervous systems. The Somatic Nervous System controls activities that are under voluntary control, such as turning the steering wheel. The Autonomic Nervous System controls activities that are not under voluntary control, such as digesting meal. Autonomic Nervous System has three divisions: sympathetic division, which controls fight - or - flight response during emergencies; parasympathetic division, which controls routine housekeeping functions of the body at other times; and enteric division, which provides local control of digestive system. You can learn more about PNS and its subdivisions by reading the concept Peripheral Nervous System.
The nervous system has three main functions: sensory input, integration of data and motor output. Sensory input is when the body gathers information or data, by way of neurons, glia and synapses. The nervous system is composed of excitable nerve cells and synapses that form between neurons and connect them to centers throughout the body or to other neurons. These neurons operate on excitation or inhibition, and although nerve cells can vary in size and location, their communication with one another determines their function. These nerves conduct impulses from sensory receptors to the brain and spinal cord. Data is then processed by way of integration of data, which occurs only in the brain. After the brain has processed information, impulses are then conducted from the brain and spinal cord to muscles and glands, which is called motor output. Glia cells are found within tissues and are not excitable but help with myelination, ionic regulation and extracellular fluid. The nervous system is comprised of two major parts, or subdivisions, central nervous system and the peripheral nervous system. Cns include the brain and spinal cord. The brain is the body's control center. Cns has various centers located within it that carry out sensory, motor and integration of data. These centers can be subdivided into Lower Centers and Higher Centers communicating with the brain via effectors. Pns is a vast network of spinal and cranial nerves that are linked to the brain and spinal cord. It contains sensory receptors which help in processing changes in the internal and external environment. This information is sent to CNS via different sensory nerves. Pns is then subdivided into autonomic nervous system and somatic nervous system. Autonomic has involuntary control of internal organs, blood vessels, smooth and cardiac muscles. Somatic has voluntary control of skin, bones, joints, and skeletal muscle. Two systems function together, by way of nerves from PNS entering and becoming part of the CNS, and vice versa. Well further discuss components and roles of these systems later in this module.
The Peripheral nervous system refers to parts of the nervous system outside the brain and spinal cord. It includes cranial nerves, spinal nerves and their roots and branches, peripheral nerves, and neuromuscular junctions. Anterior horn cells, although technically part of the central nervous system, are sometimes discussed with the peripheral nervous system because they are part of the motor unit. In peripheral nervous system, bundles of nerve bers or axons conduct information to and from the central nervous system. The autonomic nervous system is part of the nervous system concerned with innervation of involuntary structures, such as the heart, smooth muscle, and glands within the body. It is distributed throughout central and peripheral nervous systems. An Image depicting the peripheral nervous system can be seen below. Nerve cells are called neurones. Neurones consist of the cell's body, dendrites that carry electrical impulses to the cell, and long axons that carry impulses away from the cell. The of one neurone and dendrites of the next neurone do not actually touch. Gap between neurones is called synapse.S Neuronal function is complex and involves numerous processes in nerve transmission. Generation of nerve impulse of sensory neurone occurs as result of stimulus such as light, particular chemical, or stretching of cell membrane by sound. Conduction of impulse along neurone occurs from dendrites to cell body to axon. Transmission of signal to another neuron across synapse occurs via a chemical transmitter. This substance causes next neurone to be electrically stimulated and keeps signal going along nerve. Ganglia may be divided into sensory ganglia of spinal nerves and cranial nerves and autonomic ganglia. Sensory ganglia of spinal nerves are fusiform swellings situated on the posterior root of each spinal nerve just proximal to the root junction with corresponding anterior root. They are referred to as spinal or posterior root ganglia. Similar ganglia that are also found along the course of cranial nerves V, VII, VIII, IX, and X are called sensory ganglia of these nerve. Autonomic ganglia, which are often irregular in shape, are situated along course of different nerve fibers of the autonomic nervous system. They are found in paravertebral sympathetic chains, around roots of great visceral arteries in the abdomen, and close to, or embed within, walls of various viscera.
A common set of biological events take place following spinal cord injury: cells from the immune system migrate to the injury site, causing additional damage to some neurons and death to others that survive initial trauma. Death of oligodendrocytes causes axons to lose their myelination, which greatly impairs conduction of action potential, messages, or renders remaining connections useless. The Neuronal information highway is further disrupted because many axons are sever, cutting off lines of communication between the brain and muscles and between the body's sensory systems and the brain. Within several weeks of initial injury, area of tissue damage has been cleared away by microglia, and a fluid - filled cavity surrounded by glial scar is left behind. Molecules that inhibit regrowth of severed axons are now expressed at this site. Cavitation is called syrinx, which acts as a barrier to reconnection of two sides of the damaged spinal cord. Although spinal cord injury causes complex damage, surprising amount of basic circuitry to control movement and process information can remain intact. This is because the spinal cord is arranged in layers of circuitry. Many of the connections and neuronal cell bodies forming this circuitry above and below the site of injury survive trauma. An important question for research scientists is, how much do these surviving neurons know? Can they regenerate and make new, correct connections?
The smallest worker in the nervous system is the neuron. For each of chain of impulses there is one preganglionic neuron, or one before cell body or ganglion, that is like central controlling body for numerous neurons going out peripherally. Preganglionic neurons are located in either the brain or spinal cord. In autonomic nervous system, this preganglionic neuron projects to autonomic ganglion. Postganglionic neurons were then projected to target organ. In the somatic nervous system, there is only one neuron between the central nervous system and the target organ while the autonomic nervous system uses two neurons.
Plex.page is an Online Knowledge, where all the summaries are written by a machine. We aim to collect all the knowledge the World Wide Web has to offer.
© All rights reserved
2021 made by Algoritmi Vision Inc.
If you believe that any of the summaries on our website lead to misinformation, don't hesitate to contact us. We will immediately review it and remove the summaries if necessary.
If your domain is listed as one of the sources on any summary, you can consider participating in the "Online Knowledge" program, if you want to proceed, please follow these instructions to apply.
However, if you still want us to remove all links leading to your domain from Plex.page and never use your website as a source, please follow these instructions.