Nervous system

From WikiMD

The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis. Through its receptors, the nervous system keeps us in touch with our environment, both external and internal.

Like other systems in the body, the nervous system is composed of organs, principally the brain, spinal cord, nerves, and [glossary term:] ganglia. These, in turn, consist of various tissues, including nerve, blood, and connective tissue. Together these carry out the complex activities of the nervous system.

The various activities of the nervous system can be grouped together as three general, overlapping functions:

Sensory

Integrative Motor Millions of sensory receptors detect changes, called stimuli, which occur inside and outside the body. They monitor such things as temperature, light, and sound from the external environment. Inside the body, the internal environment, receptors detect variations in pressure, [glossary term:] pH, carbon dioxide concentration, and the levels of various [glossary term:] electrolytes. All of this gathered information is called sensory input.

Sensory input is converted into electrical signals called nerve impulses that are transmitted to the brain. There the signals are brought together to create sensations, to produce thoughts, or to add to memory; Decisions are made each moment based on the sensory input. This is integration.

Based on the sensory input and integration, the nervous system responds by sending signals to muscles, causing them to contract, or to glands, causing them to produce secretions. Muscles and glands are called effectors because they cause an effect in response to directions from the nervous system. This is the [glossary term:] motor output or motor function.

Nerve Tissue

Although the nervous system is very complex, there are only two main types of cells in nerve tissue. The actual nerve cell is the neuron. It is the "conducting" cell that transmits impulses and the structural unit of the nervous system. The other type of cell is neuroglia, or glial, cell. The word "neuroglia" means "nerve glue." These cells are nonconductive and provide a support system for the neurons. They are a special type of "connective tissue" for the nervous system.

Neurons

Neurons, or nerve cells, carry out the functions of the nervous system by conducting nerve impulses. They are highly specialized and amitotic. This means that if a neuron is destroyed, it cannot be replaced because neurons do not go through mitosis. The image below illustrates the structure of a typical neuron.

Cell Body

In many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell. 

Dendrites

Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers. Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called afferent processes because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an efferent process.

Axon

An axon may have infrequent branches called axon collaterals. Axons and axon collaterals terminate in many short branches or telodendria. The distal ends of the telodendria are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called [glossary term:] myelin or the myelin sheath. Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the nodes of Ranvier. In the peripheral nervous system, the myelin is produced by Schwann cells. The cytoplasm, nucleus, and outer cell membrane of the Schwann cell form a tight covering around the myelin and around the axon itself at the nodes of Ranvier. This covering is the [glossary term:] neurilemma, which plays an important role in the regeneration of nerve fibers. In the CNS, oligodendrocytes produce myelin, but there is no neurilemma, which is why fibers within the CNS do not regenerate. Functionally, neurons are classified as afferent, efferent, or interneurons (association neurons) according to the direction in which they transmit impulses relative to the central nervous system. Afferent, or sensory, neurons carry impulses from peripheral sense receptors to the CNS. They usually have long dendrites and relatively short axons. Efferent, or motor, neurons transmit impulses from the CNS to effector organs such as muscles and glands. Efferent neurons usually have short dendrites and long axons. Interneurons, or association neurons, are located entirely within the CNS in which they form the connecting link between the afferent and efferent neurons. They have short dendrites and may have either a short or long axon. 

Neuroglia

Neuroglia cells do not conduct nerve impulses, but instead, they support, nourish, and protect the neurons. They are far more numerous than neurons and, unlike neurons, are capable of mitosis.

Tumors

Schwannomas are benign tumors of the peripheral nervous system which commonly occur in their sporadic, solitary form in otherwise normal individuals. Rarely, individuals develop multiple schwannomas arising from one or many elements of the peripheral nervous system. Commonly called a Morton's Neuroma, this problem is a fairly common benign nerve growth and begins when the outer coating of a nerve in your foot thickens. This thickening is caused by irritation of branches of the medial and lateral plantar nerves that results when two bones repeatedly rub together.

The Central Nervous System

The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault, and the spinal cord is in the vertebral canal of the vertebral column. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum.

The Peripheral Nervous System

The organs of the peripheral nervous system are the nerves and ganglia. Nerves are bundles of nerve fibers, much like muscles are bundles of muscle fibers. Cranial nerves and spinal nerves extend from the CNS to peripheral organs such as muscles and glands. Ganglia are collections, or small knots, of nerve cell bodies outside the CNS.

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (motor) division. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action.

The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis. Through its receptors, the nervous system keeps us in touch with our environment, both external and internal.

Glossary

  • Abscess - noun symptom consisting of a localized collection of pus surrounded by inflamed tissue
  • Acromegaly - noun enlargement of bones of hands and feet and face; often accompanied by headache and muscle pain and emotional disturbances; caused by overproduction of growth hormone by the anterior pituitary gland (due to a tumor)
  • ACTH - noun a hormone produced by the anterior pituitary gland that stimulates the adrenal cortex
  • Acyclovir - noun an oral antiviral drug (trade name Zovirax) used to treat genital herpes; does not cure the disease but relieves the symptoms
  • Alcoholism - noun habitual intoxication; prolonged and excessive intake of alcoholic drinks leading to a breakdown in health and an addiction to alcohol such that abrupt deprivation leads to severe withdrawal symptoms; an intense persistent desire to drink alcoholic beverages to excess
  • Alzheimer's disease - noun a progressive form of presenile dementia that is similar to senile dementia except that it usually starts in the 40s or 50s; first symptoms are impaired memory which is followed by impaired thought and speech and finally complete helplessness
  • Amnesia - noun partial or total loss of memory
  • Amyotrophic lateral sclerosis - noun thickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord; results in progressive muscle atrophy that starts in the limbs
  • Anencephaly - noun a defect in brain development resulting in small or missing brain hemispheres
  • Apraxia - noun inability to make purposeful movements
  • Astereognosis - noun a loss of the ability to recognize objects by handling them
  • Ataxia - noun inability to coordinate voluntary muscle movements; unsteady movements and staggering gait
  • Athetosis - noun a continuous succession of slow, writhing, involuntary movements of the hands and feet and other body parts
  • atonia - noun lack of normal muscular tension or tonus
  • Aura - noun an indication of radiant light drawn around the head of a saint; a sensation (as of a cold breeze or bright light) that precedes the onset of certain disorders such as a migraine attack or epileptic seizure; a distinctive but intangible quality surrounding a person or thing
  • Babinski sign - noun extension upward of the toes when the sole of the foot is stroked firmly on the outer side from the heel to the front; normal in infants under the age of two years but a sign of brain or spinal cord injury in older persons
  • Balance - noun a scale for weighing; depends on pull of gravity; equality between the totals of the credit and debit sides of an account; the difference between the totals of the credit and debit sides of an account; equality of distribution; a state of equilibrium; a wheel that regulates the rate of movement in a machine; especially a wheel oscillating against the hairspring of a timepiece to regulate its beat; a weight that balances another weight; (mathematics) an attribute of a shape or relation; exact reflection of form on opposite sides of a dividing line or plane; harmonious arrangement or relation of parts or elements within a whole (as in a design); the seventh sign of the zodiac; the sun is in this sign from about September 23 to October 22; (astrology) a person who is born while the sun is in Libra; something left after other parts have been taken away; verb compute credits and debits of an account; bring into balance or equilibrium; be in equilibrium; hold or carry in equilibrium
  • basal - adj. of primary importance; serving as or forming a base; especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem
  • biopsy - noun examination of tissues or liquids from the living body to determine the existence or cause of a disease
  • Botulism - noun food poisoning from ingesting botulin; not infectious; affects the CNS; can be fatal if not treated promptly
  • brain - noun that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord; mental ability; the brain of certain animals used as meat; that which is responsible for one's thoughts and feelings; the seat of the faculty of reason; someone who has exceptional intellectual ability and originality; verb kill by smashing someone's skull; hit on the head
  • Brainstem - noun the part of the brain continuous with the spinal cord and comprising the medulla oblongata and pons and midbrain and parts of the hypothalamus
  • Broca's aphasia - noun aphasia in which expression by speech or writing is severely impaired
  • bulbar - adj. involving the medulla oblongata
  • Carpal tunnel syndrome - noun a painful disorder caused by compression of a nerve in the carpal tunnel; characterized by discomfort and weakness in the hands and fingers and by sensations of tingling, burning or numbness
  • cerebellar - adj. relating to or associated with the cerebellum
  • Cerebellum - noun a major division of the vertebrate brain; situated above the medulla oblongata and beneath the cerebrum in humans
  • Cerebral - adj. involving intelligence rather than emotions or instinct; of or relating to the cerebrum or brain
  • Cerebral death - noun death when respiration and other reflexes are absent; consciousness is gone; organs can be removed for transplantation before the heartbeat stops
  • Cerebral palsy - noun a loss or deficiency of motor control with involuntary spasms caused by permanent brain damage present at birth
  • Cerebrospinal fluid - noun clear liquid produced in the ventricles of the brain; fills and protects cavities in the brain and spinal cord
  • cervical - adj. relating to or associated with the neck; of or relating to the cervix of the uterus
  • Chorea - noun any of several degenerative nervous disorders characterized by spasmodic movements of the body and limbs; chorea in dogs
  • chromosome - noun a threadlike body in the cell nucleus that carries the genes in a linear order
  • chronic - adj. being long-lasting and recurrent or characterized by long suffering
  • CJD - noun rare (usually fatal) brain disease (usually in middle age) caused by an unidentified slow virus; characterized by progressive dementia and gradual loss of muscle control
  • classification - noun restriction imposed by the government on documents or weapons that are available only to certain authorized people; the basic cognitive process of arranging into classes or categories; a group of people or things arranged by class or category; the act of distributing things into classes or categories of the same type
  • Cognition - noun the psychological result of perception and learning and reasoning
  • Coma - noun a state of deep and often prolonged unconsciousness; usually the result of disease or injury; (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed; a usually terminal tuft of hairs especially on a seed
  • Computed tomography - noun a method of examining body organs by scanning them with X rays and using a computer to construct a series of cross-sectional scans along a single axis
  • Concussion - noun any violent blow; injury to the brain caused by a blow; usually resulting in loss of consciousness
  • Confusion - noun a mistake that results from taking one thing to be another; an act causing a disorderly combination of elements with identities lost and distinctions blended; a mental state characterized by a lack of clear and orderly thought and behavior; a feeling of embarrassment that leaves you confused; disorder resulting from a failure to behave predictably
  • convulsive - adj. affected by involuntary jerky muscular contractions; resembling a spasm; resembling a convulsion in being sudden and violent
  • cortical - adj. of or relating to a cortex
  • CT - noun a method of examining body organs by scanning them with X rays and using a computer to construct a series of cross-sectional scans along a single axis; a New England state; one of the original 13 colonies
  • Cushing's disease - noun a glandular disorder caused by excessive ACTH resulting in greater than normal functioning of the adrenal gland; characterized by obesity
  • cyanocobalamin - noun a B vitamin that is used to treat pernicious anemia
  • deficiency - noun lack of an adequate quantity or number; the state of needing something that is absent or unavailable
  • Delirium - noun a usually brief state of excitement and mental confusion often accompanied by hallucinations; state of violent mental agitation
  • Dementia - noun mental deterioration of organic or functional origin
  • Demyelination - noun loss of the myelin covering of some nerve fibers resulting in their impaired function
  • Dermatomyositis - noun myositis characterized by weakness of limb and neck muscles and much muscle pain and selling accompanied by skin rash affecting cheeks and eyelids and neck and chest and limbs; progression and severity vary among individuals
  • Differential diagnosis - noun a systematic method of diagnosing a disorder (e.g., headache) that lacks unique symptoms or signs
  • Dizziness - noun a reeling sensation; a feeling that you are about to fall
  • DM - noun a metric unit of length equal to one tenth of a meter; diabetes caused by a relative or absolute deficiency of insulin and characterized by polyuria
  • dorsal - adj. belonging to or on or near the back or upper surface of an animal or organ or part; facing away from the axis of an organ or organism
  • Down syndrome - noun a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation
  • Drunkenness - noun a temporary state resulting from excessive consumption of alcohol; the act of drinking alcoholic beverages to excess; habitual intoxication; prolonged and excessive intake of alcoholic drinks leading to a breakdown in health and an addiction to alcohol such that abrupt deprivation leads to severe withdrawal symptoms
  • dysfunction - noun (medicine) any disturbance in the function of an organ or body part
  • dysfunctional - adj. (of a trait or condition) failing to serve an adjustive purpose; impaired in function; especially of a bodily system or organ
  • EEG - noun a graphical record of electrical activity of the brain; produced by an electroencephalograph
  • Electroencephalogram - noun a graphical record of electrical activity of the brain; produced by an electroencephalograph
  • Electromyogram - noun a graphical record of electric currents associated with muscle contractions
  • embolism - noun occlusion of a blood vessel by an embolus (a loose clot or air bubble or other particle); an insertion into a calendar
  • EMG - noun a graphical record of electric currents associated with muscle contractions
  • Encephalitis - noun inflammation of the brain usually caused by a virus; symptoms include headache and neck pain and drowsiness and nausea and fever (`phrenitis' is no longer in scientific use)
  • Epilepsy - noun a disorder of the central nervous system characterized by loss of consciousness and convulsions
  • episodic - adj. limited in duration to a single episode; occurring or appearing at usually irregular intervals; of writing or narration; divided into or composed of episodes
  • Essential tremor - noun tremor of unknown cause (usually of the hands and head) that develops in older people; often mistaken for Parkinsonism but is not life-threatening and can usually be kept under control
  • evaluation - noun act of ascertaining or fixing the value or worth of; an appraisal of the value of something
  • excitatory - adj. (of drugs e.g.) able to excite or stimulate
  • fetal - adj. of or relating to a fetus
  • Fetal alcohol syndrome - noun a medical condition in which body deformation or facial development or mental ability of a fetus is impaired because the mother drank alcohol while pregnant
  • fMRI - noun a form of magnetic resonance imaging of the brain that registers blood flow to functioning areas of the brain
  • focal - adj. having or localized centrally at a focus; of or relating to a focus
  • Focal seizure - noun transitory disturbance in motor or sensory function resulting from abnormal cortical activity
  • gait - noun a person's manner of walking; a horse's manner of moving; the rate of moving (especially walking or running)
  • Glioma - noun a tumor of the brain consisting of neuroglia
  • glutamate - noun a salt or ester of glutamic acid
  • Hematoma - noun a localized swelling filled with blood
  • hemorrhage - noun flow of blood from a ruptured blood vessels; verb lose blood from one's body
  • Horner's syndrome - noun a pattern of symptoms occurring as a result of damage to nerves in the cervical region of the spine (drooping eyelids and constricted pupils and absence of facial sweating)
  • Hyponatremia - noun abnormally low level of sodium in the blood; associated with dehydration
  • I - noun the 9th letter of the Roman alphabet; a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)
  • Index - noun the finger next to the thumb; an alphabetical listing of names and topics along with page numbers where they are discussed; a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time; a numerical scale used to compare variables with one another or with some reference number; a mathematical notation indicating the number of times a quantity is multiplied by itself; verb adjust through indexation; provide with an index; list in an index
  • Index - noun the finger next to the thumb; an alphabetical listing of names and topics along with page numbers where they are discussed; a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of time; a numerical scale used to compare variables with one another or with some reference number; a mathematical notation indicating the number of times a quantity is multiplied by itself; verb adjust through indexation; provide with an index; list in an index
  • Insomnia - noun an inability to sleep; chronic sleeplessness
  • Intelligence - noun the operation of gathering information about an enemy; the ability to comprehend; to understand and profit from experience; secret information about an enemy (or potential enemy); a unit responsible for gathering and interpreting information about an enemy; new information about specific and timely events
  • ischemia - noun local anemia in a given body part sometimes resulting from vasoconstriction or thrombosis or embolism
  • ischemic - adj. relating to or affected by ischemia
  • Language - noun the mental faculty or power of vocal communication; a systematic means of communicating by the use of sounds or conventional symbols; the cognitive processes involved in producing and understanding linguistic communication; a system of words used to name things in a particular discipline; the text of a popular song or musical-comedy number; (language) communication by word of mouth
  • Levodopa - noun the levorotatory form of dopa (trade names Bendopa and Brocadopa and Larodopa); as a drug it is used to treat Parkinson's disease
  • LP - noun a long-playing phonograph record; designed to be played at 33.3 rpm
  • Lumbar puncture - noun removal by centesis of fluid from the subarachnoid space of the lumbar region of the spinal cord for diagnostic or therapeutic purposes
  • Malformation - noun something abnormal or anomalous; an affliction in which some part of the body is misshapen or malformed
  • management - noun the act of managing something; those in charge of running a business
  • Medulla - noun the inner part of an organ or structure in plant or animal; lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata); a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers
  • Memory - noun an electronic memory device; the power of retaining and recalling past experience; the cognitive processes whereby past experience is remembered; something that is remembered; the area of cognitive psychology that studies memory processes
  • Meningioma - noun a tumor arising in the meninges which surround the brain and spinal cord; usually slow growing and sometimes malignant
  • mental - adj. affected by a disorder of the mind; involving the mind or an intellectual process; of or relating to the chin- or liplike structure in insects and certain mollusks; of or relating to the mind; of or relating to the chin or median part of the lower jaw
  • Metabolic - adj. undergoing metamorphosis; of or relating to metabolism
  • MG - noun one thousandth (1/1,000) gram; a light silver-white ductile bivalent metallic element; in pure form it burns with brilliant white flame; occurs naturally only in combination (as in magnesite and dolomite and carnallite and spinel and olivine)
  • migraine - noun a severe recurring vascular headache; occurs more frequently in women than men
  • MRI - noun the use of nuclear magnetic resonance of protons to produce proton density images
  • MS - noun a form of address for a woman; the form of a literary work submitted for publication; a master's degree in science; a state in the Deep South on the gulf of Mexico; one of the Confederate States during the American Civil War; a chronic progressive nervous disorder involving loss of myelin sheath around certain nerve fibers
  • Multiple sclerosis - noun a chronic progressive nervous disorder involving loss of myelin sheath around certain nerve fibers
  • muscle - noun authority or power or force (especially when used in a coercive way); animal tissue consisting predominantly of contractile cells; one of the contractile organs of the body; possessing muscular strength; a bully employed as a thug or bodyguard; verb make one's way by force
  • Muscular dystrophy - noun any of several hereditary diseases of the muscular system characterized by weakness and wasting of skeletal muscles
  • myasthenia gravis - noun a chronic progressive disease characterized by chronic fatigue and muscular weakness (especially in the face and neck); caused by a deficiency of acetylcholine at the neuromuscular junctions
  • Myasthenia gravis - noun a chronic progressive disease characterized by chronic fatigue and muscular weakness (especially in the face and neck); caused by a deficiency of acetylcholine at the neuromuscular junctions
  • Myelin - noun a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers
  • myoclonus - noun a clonic spasm of a muscle or muscle group
  • Narcolepsy - noun a sleep disorder characterized by sudden and uncontrollable episodes of deep sleep
  • necrotic - adj. relating to or affected by necrosis
  • normal - adj. conforming with or constituting a norm or standard or level or type or social norm; not abnormal; being approximately average or within certain limits in e.g. intelligence and development; in accordance with scientific laws; forming a right angle; noun something regarded as a normative example
  • NP - noun a registered nurse who has received special training and can perform many of the duties of a physician; a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium
  • NREM - noun a recurring sleep state during which rapid eye movements do not occur and dreaming does not occur; accounts for about 75% of normal sleep time
  • Nystagmus - noun involuntary movements of the eyeballs; its presence or absence is used to diagnose a variety of neurological and visual disorders
  • Pain - noun a somatic sensation of acute discomfort; emotional distress; a fundamental feeling that people try to avoid; a bothersome annoying person; a symptom of some physical hurt or disorder; something or someone that causes trouble; a source of unhappiness; verb cause emotional anguish or make miserable; cause bodily suffering to and make sick or indisposed
  • Paraparesis - noun a slight paralysis or weakness of both legs
  • Paresthesia - noun abnormal skin sensations (as tingling or tickling or itching or burning) usually associated with peripheral nerve damage
  • Parkinson's disease - noun a degenerative disorder of the central nervous system characterized by tremor and impaired muscular coordination
  • PD - noun a silver-white metallic element of the platinum group that resembles platinum; occurs in some copper and nickel ores; does not tarnish at ordinary temperatures and is used (alloyed with gold) in jewelry
  • pediatric - adj. of or relating to the medical care of children
  • Phenylketonuria - noun a genetic disorder of metabolism; lack of the enzyme needed to turn phenylalanine into tyrosine results in an accumulation of phenylalanine in the body fluids which causes various degrees of mental deficiency
  • PKU - noun a genetic disorder of metabolism; lack of the enzyme needed to turn phenylalanine into tyrosine results in an accumulation of phenylalanine in the body fluids which causes various degrees of mental deficiency
  • Pons - noun a band of nerve fibers linking the medulla oblongata and the cerebellum with the midbrain; United States coloratura soprano (born in France) (1904-1976)
  • primary - adj. not derived from or reducible to something else; basic; of first rank or importance or value; direct and immediate rather than secondhand; of primary importance; most important element; of or being the essential or basic part; noun a preliminary election where delegates or nominees are chosen; one of the main flight feathers projecting along the outer edge of a bird's wing; coil forming the part of an electrical circuit such that changing current in it induces a current in a neighboring circuit
  • Prion - noun (microbiology) an infectious protein particle similar to a virus but lacking nucleic acid; thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system
  • protein - noun any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes
  • Rapid eye movement sleep - noun a recurring sleep state during which dreaming occurs; a state of rapidly shifting eye movements during sleep
  • segmental - adj. divided or organized into speech segments or isolable speech sounds; having the body divided into successive metameres or segments, as in earthworms or lobsters
  • Seizure - noun the taking possession of something by legal process; a sudden occurrence (or recurrence) of a disease; the act of forcibly dispossessing an owner of property; the act of taking of a person by force
  • serum - noun watery fluid of the blood that resembles plasma but contains fibrinogen
  • sheath - noun a protective covering for a knife or sword; an enveloping structure or covering enclosing an animal or plant organ or part; a dress suitable for formal occasions
  • skeletal - adj. of or relating to or forming or attached to a skeleton; very thin especially from disease or hunger or cold
  • Skeletal muscle - noun a muscle that is connected at either or both ends to a bone and so move parts of the skeleton; a muscle that is characterized by transverse stripes
  • skull - noun the bony skeleton of the head of vertebrates
  • Sleep - noun a natural and periodic state of rest during which consciousness of the world is suspended; a torpid state resembling deep sleep; a period of time spent sleeping; euphemisms for death (based on an analogy between lying in a bed and in a tomb); verb be asleep; be able to accommodate for sleeping
  • Smooth muscle - noun muscle tissue that does not appear striated under the microscope; has the form of thin layers or sheets; a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)
  • spastic - adj. suffering from spastic paralysis; relating to or characterized by spasm; affected by involuntary jerky muscular contractions; resembling a spasm; noun a person suffering from spastic paralysis
  • Spinal cord - noun a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain; a long tubelike structure extending from the base of the brain through the vertebral canal to the upper lumbar region
  • Status epilepticus - noun a condition in which there are continuing attacks of epilepsy without intervals of consciousness; can lead to brain damage and death
  • Stroke - noun a light touch with the hands; a single complete movement; (sports) the act of swinging or striking at a ball with a club or racket or bat or cue or hand; any one of the repeated movements of the limbs and body used for locomotion in swimming or rowing; a mark made by a writing implement (as in cursive writing); a light touch; the oarsman nearest the stern of the shell who sets the pace for the rest of the crew; a sudden loss of consciousness resulting when the rupture or occlusion of a blood vessel leads to oxygen lack in the brain; a punctuation mark (/) used to separate related items of information; the maximum movement available to a pivoted or reciprocating piece by a cam; verb treat gingerly or carefully; strike a ball with a smooth blow; row at a particular rate; touch lightly and with affection, with brushing motions
  • Stupor - noun marginal consciousness; the feeling of distress and disbelief that you have when something bad happens accidentally
  • subdural - adj. below the dura mater but above the arachnoid membrane of the meninges
  • Synapse - noun the junction between two neurons (axon-to-dendrite) or between a neuron and a muscle
  • syndrome - noun a complex of concurrent things; a pattern of symptoms indicative of some disease
  • Syndrome - noun a complex of concurrent things; a pattern of symptoms indicative of some disease
  • thrombosis - noun the formation or presence of a thrombus (a clot of coagulated blood attached at the site of its formation) in a blood vessel
  • TIA - noun brief episode in which the brain gets insufficient blood supply; symptoms depend on the site of the blockage
  • Transient ischemic attack - noun brief episode in which the brain gets insufficient blood supply; symptoms depend on the site of the blockage
  • trauma - noun an emotional wound or shock often having long-lasting effects; any physical damage to the body caused by violence or accident or fracture etc.
  • Tremor - noun an involuntary vibration (as if from illness or fear); a small earthquake; shaking or trembling (usually resulting from weakness or stress or disease); verb shake with seismic vibrations
  • Trisomy - noun chrosomal abnormality in which there is one more than the normal number of chromosomes in a cell
  • vascular - adj. of or relating to or having vessels that conduct and circulate fluids
  • Vertigo - noun a reeling sensation; a feeling that you are about to fall
  • Vestibular system - noun organs mediating the labyrinthine sense; concerned with equilibrium
  • Vitamin B - noun originally thought to be a single vitamin but now separated into several B vitamins
  • Wernicke's aphasia - noun aphasia characterized by fluent but meaningless speech and severe impairment of the ability understand spoken or written words
edit 

WikiMD Resources - Nervous system


Help WikiMD:Join WikiMD as an an editor and help improve the page Nervous system or others.
W8MD weight loss logo

Ad. Tired of being overweight?. W8MD's insurance Weight loss program can HELP*

Quick links: Medicine Portal | Encyclopedia‏‎‏‎ | Gray's Anatomy‏‎ | Topics‏‎ |‏‎ Diseases‏‎ | Drugs | Wellness | Obesity‏‎ | Metabolic syndrome | Weight loss*
Disclaimer: The entire contents of WIKIMD.ORG are for informational purposes only and do not render medical advice or professional services. If you have a medical emergency, you should CALL 911 immediately! Given the nature of the wiki, the information provided may not be accurate, misleading and or incorrect. Use the information on this wiki at your own risk! See full Disclaimer.
Link to this page: <a href="http://www.wikimd.org/wiki/Nervous_system">Nervous system</a>

  • Individual results may vary for weight loss from our sponsors.