autonomic nervous system

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autonomic

 [aw″to-nom´ik]
not subject to voluntary control.
autonomic dysreflexia an uninhibited and exaggerated reflex of the autonomic nervous system to stimulation; called also hyperreflexia. The response occurs in 85 per cent of all patients who have spinal cord injury above the level of the sixth thoracic vertebra. It is potentially dangerous because of attendant vasoconstriction and immediate elevation of blood pressure, which in turn can bring about hemorrhagic retinal damage or stroke syndrome. Less serious effects include severe headache; changes in heart rate; sweating, flushing, and “goose bumps” or piloerection above the level of the spinal cord injury; and pallor below that level.
Patient Care. Circumstances that can trigger autonomic dysreflexia are often related to stimulation of the bladder, bowel, and skin of the patient. Examples are a distended bowel or bladder, pressure on the skin, or any of a number of noxious stimuli.

Once the symptoms of autonomic dysreflexia are manifest, emergency care is indicated. Efforts are made to lower the blood pressure by placing the patient in a sitting position or elevating the head and upper body to a 45-degree angle. The stimulus must be identified and removed as gently and quickly as possible. If fecal impaction is the cause, the rectum should be coated with an anesthetic ointment prior to attempted removal of the impaction; this prevents increasing the stimulus to autonomic dysreflexia. The physician is notified so that appropriate medical intervention can be initiated. Antihypertensive drugs are a last resort. As soon as the cause is identified and removed, the dysreflexia will disappear. Patients who experience repeated attacks may require surgery to sever the nerves responsible for the exaggerated response to stimulation.
autonomic nervous system the branch of the nervous system that works without conscious control. The voluntary nervous system governs the striated or skeletal muscles, whereas the autonomic nervous system governs the glands, cardiac muscle, and smooth muscles such as those of the digestive system, respiratory system, and skin. The autonomic nervous system is divided into two subsidiary systems, the sympathetic nervous system and the parasympathetic nervous system. See Plate 14.

system

 [sis´tem]
1. a set or series of interconnected or interdependent parts or entities (objects, organs, or organisms) that act together in a common purpose or produce results impossible by action of one alone.
2. an organized set of principles or ideas. adj., adj systemat´ic, system´ic.

The parts of a system can be referred to as its elements or components; the environment of the system is defined as all of the factors that affect the system and are affected by it. A living system is capable of taking in matter, energy, and information from its environment (input), processing them in some way, and returning matter, energy, and information to its environment as output.

An open system is one in which there is an exchange of matter, energy, and information with the environment; in a closed system there is no such exchange. A living system cannot survive without this exchange, but in order to survive it must maintain pattern and organization in the midst of constant change. Control of self-regulation of an open system is achieved by dynamic interactions among its elements or components. The result of self-regulation is referred to as the steady state; that is, a state of equilibrium. homeostasis is an assemblage of organic regulations that act to maintain steady states of a living organism.

A system can be divided hierarchically into subsystems, which can be further subdivided into sub-subsystems and components. A system and its environment could be considered as a unified whole for purposes of study, or a subsystem could be studied as a system. For example, the collection of glands in the endocrine system can be thought of as a system, each endocrine gland could be viewed as a system, or even specific cells of a single gland could be studied as a system. It is also possible to think of the human body as a living system and the endocrine system as a subsystem. The division of a system into a subsystem and its environment is dependent on the perspective chosen by the person studying a particular phenomenon.
Systems, subsystems, and suprasystems. Within the environment there are suprasystems, such as human society, and systems within the suprasystem, such as the educational and industrial systems and the health care delivery system. Within the health care delivery system are subsystems, such as the patient, family members, the nurse, the physician, and allied health care professionals and paraprofessionals.
alimentary system digestive system.
apothecaries' system see apothecaries' system.
autonomic nervous system see autonomic nervous system.
avoirdupois system see avoirdupois system.
behavioral system in the behavioral system model of nursing, the patterned, repetitive, and purposeful behaviors of an individual.
cardiovascular system the heart and blood vessels, by which blood is pumped and circulated through the body; see also circulatory system.
CD system (cluster designation) a system for classifying cell-surface markers expressed by lymphocytes based on a computer analysis of monoclonal antibodies against hla antigens, with antibodies having similar specificity characteristics being grouped together and assigned a number (CD1, CD2, CD3, etc.); these CD numbers are also applied to the specific antigens recognized by the various groups of monoclonal antibodies. See also CD antigen.
centimeter-gram-second system (CGS) (cgs) a system of measurements in which the units are based on the centimeter as the unit of length, the gram as the unit of mass, and the second as the unit of time.
central nervous system see central nervous system.
centrencephalic system the neurons in the central core of the brainstem from the thalamus to the medulla oblongata, connecting the cerebral hemispheres.
circulatory system see circulatory system.
client system in the general systems framework and theory of goal attainment, the composite of physiological, psychological, sociocultural, and developmental variables that make up the total person.
colloid system (colloidal system) colloid (def. 3).
conduction system (conductive system (of heart)) the system of atypical cardiac muscle fibers, comprising the sinoatrial and atrioventricular nodes, internodal tracts, atrioventricular bundle, bundle branch, and terminal ramifications into the Purkinje network.
digestive system see digestive system.
Emergency Medical Services (EMS) system a comprehensive program designed to provide services to the patient in the prehospital setting. The system is activated when a call is made to the EMS operator, who then dispatches an ambulance to the patient. The patient receives critical interventions and is stabilized at the scene. A communication system allows the health care workers at the scene to contact a trauma center for information regarding further treatment and disposition of the patient, followed by transportation of the patient to the most appropriate facility for treatment.
endocrine system the system of ductless glands and other structures that produce internal secretions (hormones) that are released directly into the circulatory system, influencing metabolism and other body processes; see endocrine glands.
environmental control system environmental control unit.
expert system a set of computer programs designed to serve as an aid in decision making.
extrapyramidal system see extrapyramidal system.
gateway system a software interface between an online searcher and one or more search systems, facilitating the use of the system by searchers who are unfamiliar with it, or with online retrieval in general.
genitourinary system the organs concerned with production and excretion of urine, together with the reproductive organs. (See Plates.) Called also urogenital system.
haversian system a haversian canal and its concentrically arranged lamellae, constituting the basic unit of structure in compact bone (osteon).
Haversian system: Structures of compact and spongy bone with the central haversian canal surrounded by the lamellae. From Applegate, 2000.
health care system see health care system.
heterogeneous system a system or structure made up of mechanically separable parts, as an emulsion or suspension.
His-Purkinje system the intraventricular conduction system from the bundle of His to the distal Purkinje fibers, which carries the impulse to the ventricles.
Home Health Care Classification system see home health care classification system.
homogeneous system a system or structure made up of parts that cannot be mechanically separated, as a solution.
hypophyseoportal system (hypophysioportal system) (hypothalamo-hypophysial portal system) the venules connecting the hypothalamus with the sinusoidal capillaries of the anterior lobe of the pituitary gland; they carry releasing substances to the pituitary.
immune system see immune system.
interpersonal system in the general systems framework and theory of goal attainment, two or more individuals interacting in a given situation.
lay health system a system comprising an informal referral network and sources of treatment outside the formal biomedical sources of health care; it includes individual consultation and information-seeking through significant others and peers concerning health behaviors, symptoms, and evaluation of treatment before, during, and after consultation with health care professionals.
legal system in the omaha system, anything connected with law or its administration; it includes legal aid, attorney, courts, or Child Protective Services (CPS), and many other agencies and officials.
limbic system a system of brain structures common to the brains of all mammals, comprising the phylogenetically old cortex (archipallium and paleopallium) and its primarily related nuclei. It is associated with olfaction, autonomic functions, and certain aspects of emotion and behavior.
lymphatic system see lymphatic system.
lymphoid system the lymphoid tissue of the body, collectively; it consists of primary (or central) lymphoid tissues, the bone marrow, and thymus, and secondary (or peripheral) tissues, the lymph nodes, spleen, and gut-associated lymphoid tissue (tonsils, Peyer's patches).
lymphoreticular system the lymphoid and reticuloendothelial systems considered together; see also lymphoreticular disorders.
metric system see metric system.
mononuclear phagocyte system the group of highly phagocytic cells that have a common origin from stem cells of the bone marrow and develop circulating monocytes and tissue macrophages, which develop from monocytes that have migrated to connective tissue of the liver (kupffer's cells), lung, spleen, and lymph nodes. The term has been proposed to replace reticuloendothelial system, which includes some cells of different origin and does not include all macrophages.
nervous system see nervous system.
nursing system in the self-care model of nursing, all the actions and interactions of nurses and patients in nursing practice situations; nursing systems fall into three categories: wholly compensatory, partly compensatory, and supportive-educative.
Omaha system see omaha system.
oxygen delivery system a device that delivers oxygen through the upper airways to the lungs at concentrations above that of ambient air. There are two general types: the fixed performance or high flow type, which can supply all of the needs of a patient for inspired gas at a given fractional inspired oxygen; and the variable performance or low flow type, which cannot supply all of the patient's needs for oxygen and delivers fractional inspired oxygen that varies with ventilatory demand.
parasympathetic nervous system see parasympathetic nervous system.
peripheral nervous system the portion of the nervous system consisting of the nerves and ganglia outside the brain and spinal cord.
personal system in the general systems framework and theory of goal attainment, the unified self, a complex whole that is rational, conscious, and feeling and that sets goals and decides on the means of achieving them.
pituitary portal system hypothalamo-hypophysial portal system.
portal system an arrangement by which blood collected from one set of capillaries passes through a large vessel or vessels and another set of capillaries before returning to the systemic circulation, as in the pituitary gland (the hypothalamo-hypophysial portal system) or the liver (the hepatic portal circulation).
renin-angiotensin-aldosterone system see renin-angiotensin-aldosterone system.
respiratory system the group of specialized organs whose specific function is to provide for the transfer of oxygen from the air to the blood and of waste carbon dioxide from the blood to the air. The organs of the system include the nose, the pharynx, the larynx, the trachea, the bronchi, and the lungs. See also respiration and Plates 7 and 8.
reticular activating system see reticular activating system.
reticuloendothelial system see reticuloendothelial system.
safety system see safety system.
SI system see SI units.
skeletal system see skeletal system.
social system in the general systems framework and theory of goal attainment, an organized boundary system of social roles, behaviors, and practices developed to maintain balance for growth, development, and performance, which involves an exchange of energy and information between the person and the environment for regulation and control of stressors.
support system in the omaha system, the circle of friends, family, and associates that provide love, care, and need gratification; it may include church, school, workplace, or other groupings.
sympathetic nervous system see sympathetic nervous system.
Unified Medical Language system see unified medical language system.
Unified Nursing Language system see unified nursing language system.
unit dose system a method of delivery of patient medications directly to the patient care unit. Following review by a nurse, a copy of the physician's original order is sent to the pharmacy, where the pharmacist reviews it again. The pharmacist then fills the order and delivers the medication to the patient care unit, usually in a 24-hour supply. Each patient has an individual supply of medications prepared and labeled by the pharmacist.
urinary system the system formed in the body by the kidneys, ureters, urinary bladder, and urethra, the organs concerned in the production and excretion of urine.
urogenital system genitourinary system.
vascular system circulatory system.
vasomotor system the part of the nervous system that controls the caliber of the blood vessels.

autonomic (visceral motor) division of nervous system

[TA]
that part of the nervous system that represents the motor innervation of smooth muscle, cardiac muscle, and gland cells. It consists of two physiologically and anatomically distinct, mutually antagonistic components: the sympathetic and parasympathetic parts. In both these parts, the pathway of innervation consists of a synaptic sequence of two motor neurons, one of which lies in the spinal cord or brainstem as the presynaptic (also called preganglionic or B fiber) neuron, the thin but myelinated axon of which emerges with an outgoing spinal or cranial nerve and synapses with one or more of the postsynaptic (postganglionic or, more strictly, ganglionic) neurons composing the autonomic ganglia; the unmyelinated postsynaptic fibers in turn innervate the smooth muscle, cardiac muscle, or gland cells. The presynaptic neurons of the sympathetic part lie in the intermediolateral cell column of the thoracic and upper two lumbar segments of the spinal gray matter; those of the parasympathetic part compose the visceral motor (visceral efferent) nuclei of the brainstem as well as the lateral column of the second to fourth sacral segments of the spinal cord. The ganglia of the sympathetic part are the paravertebral ganglia of the sympathetic trunk and the lumbar and sacral prevertebral or collateral ganglia; those of the parasympathetic part lie either near the organ to be innervated or as intramural ganglia within the organ itself except in the head, where there are four discrete parasympathetic ganglia (ciliary, otic, pterygopalatine, and submandibular). Impulse transmission from presynaptic to postsynaptic neuron is mediated by acetylcholine in both the sympathetic and parasympathetic parts; transmission from the postsynaptic fiber to the visceral effector tissues is classically said to be by acetylcholine in the parasympathetic part and by noradrenalin in the sympathetic part; recent evidence suggests the existence of further noncholinergic, nonadrenergic classes of postsynaptic fibers.

autonomic nervous system

n.
The part of the vertebrate nervous system that regulates involuntary action, as of the intestines, heart, and glands, and that is divided into the sympathetic nervous system and the parasympathetic nervous system.

autonomic nervous system

the part of the nervous system that regulates involuntary body functions, including the activity of the cardiac muscle, smooth muscles, and glands. It has two divisions: The sympathetic nervous system accelerates heart rate, constricts blood vessels, and raises blood pressure; the parasympathetic nervous system slows heart rate, increases intestinal peristalsis and gland activity, and relaxes sphincters.

au·to·no·mic di·vi·sion of ner·vous sys·tem

(aw'tō-nom'ik di-vizh'ŭn nĕr'vŭs sis'tĕm)
That part of the nervous system that represents the motor innervation of smooth muscle, cardiac muscle, and gland cells. It consists of two physiologically and anatomically distinct, mutually antagonistic components: the sympathetic and parasympathetic parts. In both of these parts the pathway of innervation consists of a synaptic sequence of two motor neurons, one of which lies in the spinal cord or brainstem as the presynaptic (preganglionic) neuron, the thin but myelinated axon of which (preganglionic [presynaptic] or B fiber) emerges with an outgoing spinal or cranial nerve and synapses with one or more of the postsynaptic (postganglionic or, more strictly, ganglionic) neurons comprising the autonomic ganglia; theunmyelinated postsynaptic fibers in turn innervate the smooth muscle, cardiac muscle, or gland cells. The presynaptic neurons of the sympathetic part lie in the intermediolateral cell column of the thoracic and upper two lumbar segments of the spinal gray matter; those of the parasympathetic part comprise the visceral motor (visceral efferent) nuclei of the brainstem as well as the lateral column of the second to fourth sacral segments of the spinal cord. The ganglia of the sympathetic part are the paravertebral ganglia of the sympathetic trunk and the lumbar and sacral prevertebral or collateral ganglia; those of the parasympathetic part lie either near the organ to be innervated or as intramural ganglia within the organ itself except in the head, where there are four discrete parasympathetic ganglia (ciliary, otic, pterygopalatine, and submandibular). Impulse transmission from presynaptic to postsynaptic neuron is mediated by acetylcholine in both the sympathetic and parasympathetic parts; transmission from the postsynaptic fiber to the visceral effector tissues is classically said to be by acetylcholine in the parasympathetic part and by noradrenalin in the sympathetic part; recent evidence suggests the existence of further noncholinergic, nonadrenergic classes of postsynaptic fibers.
Synonym(s): divisio autonomica systematis nervosi peripherici [TA] , autonomic nervous system.

autonomic nervous system

,

ANS

Enlarge picture
AUTONOMIC NERVOUS SYSTEM
The parts of the nervous system that control unconscious, involuntary, and visceral body functions. The autonomic nervous system reflexively balances the body's smooth muscle tone, blood pressure, temperature, fluid composition, state of digestion, metabolic activity, and sexual activation. In the central nervous system (CNS), the activities of the autonomic nervous system (ANS) are coordinated in the brainstem (especially in the nucleus of the tractus solitarius) and in the hypothalamus. In the peripheral nervous system (PNS), the ANS comprises the visceral motor axons, the visceral sensory axons, and the enteric nervous system (a neural net within the walls of the gastrointestinal tract). Compared to peripheral somatic axons, the peripheral autonomic axons tend to be small (less than 3 µm in diameter), slowly conducting, and sparsely myelinated. The autonomic motor circuits also differ from somatic motor pathways. Peripheral somatic motor pathways, i.e., the circuitry sending signals to skeletal muscles, are only one axon long; axons of somatic motor neurons in the spinal cord and brainstem synapse directly on the effector cell, a muscle cell. In contrast, peripheral autonomic motor pathways are two axons long. First, an axon (a preganglionic axon) of a visceral motor neuron in the spinal cord or brainstem synapses on a neuron in a peripheral ganglion. Second, the axon (a postganglionic axon) of the ganglion neuron synapses on the effector cell, a smooth muscle cell, a cardiac muscle cell, or a secretory cell.

This autonomic motor circuitry is further subdivided into two parallel subsystems; the sympathetic and the parasympathetic. The subsystems differ in two major ways: 1. In the sympathetic system, the central (preganglionic) neurons are located only in the thoracic and lumbar segments of the spinal cord; in the parasympathetic system, the central neurons are located only in the brainstem and in a short segment of the caudal end of the spinal cord. 2. In the sympathetic system, norepinephrine is the characteristic neurotransmitter of the postganglionic axons; in the parasympathetic system, acetylcholine is the characteristic neurotransmitter of the postganglionic axons. In both the sympathetic and parasympathetic systems, the characteristic neurotransmitter of the preganglionic axons is acetylcholine.Besides their characteristic neurotransmitters, autonomic nerves influence surrounding tissues through the release of other active chemicals including ATP, nitric oxide, and a range of peptides, e.g., substance P and vasoactive intestinal peptide. As a result of their different final transmitters, the effects of the two subsystems differ. Sympathetic stimulation readies an animal for interaction with the outside world and prepares the animal for "fight or flight"; e.g., activation of sympathetic axons increases heart rate and decreases gastrointestinal peristalsis. On the other hand, parasympathetic stimulation relaxes and quiets an animal; e.g., activation of parasympathetic axons decreases heart rate and increases gastrointestinal peristalsis. The accompanying table compares the effects of sympathetic and parasympathetic stimulation on specific tissues. See: parasympathetic nervous system; sympathetic nervous system; illustrationtable

Pathology

The ANS is distributed throughout the body, and autonomic dysfunction can produce a wide range of symptoms, such as bladder malfunction, blood pressure abnormalities, breathing difficulty, gastrointestinal motility problems, heart arrhythmias, impotence, nasal congestion, sweating disorders, syncope, and visual symptoms. Drugs that act on or mimic autonomic neurotransmitters are commonly used to alleviate these symptoms as well as other conditions, such as glaucoma, heart failure, shock, and thyroid storm. To assess the overall functioning of the ANS, physicians often begin with simple measurements of the reflexive responses of the cardiovascular system; specifically, they measure the changes of blood pressure and heart rate as a person stands from sitting and exercises.

Tissue:Effects:
Sympathetic StimulationParasympathetic Stimulation
adipose tissuelipolysis
adrenal cortex
secretion (corticoids)increase
adrenal medulla
secretion (adrenaline)increase
arteries
abdominal organsconstriction
coronarydilation
skin and mucosaconstriction
bladder
wall (detrusor) musclerelaxationcontraction
sphinctercontractionrelaxation
gall bladder
wall musclerelaxationcontraction
ductdilationconstriction
heart
AV node (conduction velocity)increasedecrease
SA node (rate)increasedecrease
atrial muscle (contractility)increasedecrease
ventricular muscle (contractility)increase
intestine
wall muscle (tone and motility)decreaseincrease
secretiondecreaseincrease
rectal sphincter musclecontractionrelaxation
kidney
secretion (renin)increase
lacrimal gland
secretion (tears)increase
liver
metabolismglycogenolysis, gluconeogenesisglycogen synthesis
bile secretiondecreaseincrease
lung
airwaysdilationconstriction
secretion (airway glands)increase
nasopharynx
secretion (mucosal glands)increase
pancreas
secretion (enzymes and insulin)decreaseincrease
secretion (glucagon)increase
pineal gland
melatonin synthesisstimulation
pupildilationconstriction
reproductive tract
musclescontractions
blood vesselsconstrictiondilation, erection
salivary gland
secretiondecreaseincrease
skeletal muscleincrease contractility, glycogenolysis
skin
pilomotor musclecontraction
secretion (sweat)increase
spleen
capsulecontraction
stomach
wall muscle (tone and motility)decreaseincrease
secretiondecreaseincrease
uterus
pregnantcontraction
nonpregnantrelaxation

autonomic nervous system

The part of the nervous system controlling involuntary functions, such as the heart beat, the secretion of glands and the contraction of blood vessels. It is subdivided into the SYMPATHETIC and the PARASYMPATHETIC divisions which are, in general, antagonistic and in balance. The term autonomic derives from the Greek autos , self, and nomos , a law.

autonomic nervous system

the part of the nervous system that controls the involuntary activities of the body There are two main parts:
  1. The sympathetic nervous system., in which complexes of SYNAPSES form ganglia alongside the vertebrae, and the preganglionic fibres from the central nervous system are therefore short; the fibres are ADRENERGIC. (b) The parasympathetic nervous system, in which the ganglia are embedded in the wall of the effector so that the preganglionic fibres are long and the postganglionic fibres short; these are CHOLINERGIC.

sympathetic system inhibits peristalsis stimulates contraction in sphincters of bladder and anus inhibits bladder contraction stimulates pacemaker, speeding up heart stimulates arterial constriction inhibits contraction of bronchioles, causing dilation inhibits contraction of iris muscle, causing dilated pupil parasympathetic system stimulates peristalis inhibits contraction in sphincters of bladder and anus stimulates bladder contraction inhibits pacemaker, slowing down heart inhibits arterial constriction, causing dilation stimulates contraction of bronchioles stimulates contraction of iris muscle, causing reduced pupil.

The sympathetic and parasympathetic systems innervate the same end organs, but the effects produced by the two systems generally oppose one another, for example:

Autonomic nervous system (ANS)

The part of the nervous system that supplies nerve endings in the blood vessels, heart, intestines, glands, and smooth muscles, and governs their involuntary functioning. The autonomic nervous system is responsible for the biochemical changes involved in experiences of anxiety.

autonomic nervous system

; ANS the involuntary nervous system regulating systemic function and blood flow; under overall hypothalamic control and inputting to homeostatic mechanisms; divided into sympathetic and parasympathetic divisions

autonomic nervous system (·tō·nˑ·mik nerˑ·vs siˑ·stm),

n involuntary nervous system con-sisting of the sympathetic and the parasympathetic subsystems.
Enlarge picture
Autonomic nervous system.

au·to·nom·ic

(aw'tō-nom'ik)
Relating to the autonomic nervous system.

autonomic

not subject to voluntary control.

autonomic craniosacral outflow
the parasympathetic nervous system includes nerve fibers in the oculomotor, facial and glossopharyngeal and vagal cranial nerves. The sacral outflow includes autonomic fibers in the ventral nerve roots of the sacral nerves.
autonomic drug
drugs that have effects similar to those of the effector agents in the two systems are called sympathomimetic and parasympathomimetic drugs.
autonomic ganglionic blocking agent
nicotine and some synthetic compounds such as hexamethonium, pentamethonium and others specifically paralyze the nerve cells in autonomic ganglia thus neutralizing the sympathetic and parasympathic postganglionic fibers that emanate from that particular ganglion.
autonomic nervous system
see autonomic nervous system.
autonomic parasympathetic effects
include constriction of the pupil and the bronchioles, increased secretory activity of glands, increased tone and motility of the gut, relaxation of the sphincters.
autonomic reflex arc
comprises the afferent fibers from sensory end organs which pass into the spinal cord via the dorsal roots, ascend through the sensory columns in the spinal cord to the hypothalamus. Efferent fibers pass from there to subhypothalamic motor levels.
autonomic sympathetic effects
include the fight-or-flight reactions of dilatation of blood vessels to muscles, constriction of others, dilatation of pupils and bronchioles, and inhibition of glandular and plain muscle activity.
autonomic thoracolumbar outflow
the sympathetic nervous system consists of neurons in the intermediolateral gray column of the thoracic and lumbar segments of the spinal cord which leave the cord in the ventral branches of thoracic and lumbar nerves. Once outside the vertebral column the neurons leave the spinal nerve and join the paravertebral sympathetic trunk to enter ganglia from which postganglionic fibers go their separate ways to effector organs.

nervous

1. pertaining to a nerve or nerves.
2. unduly excitable.

nervous acetonemia
in contrast to the more common form of this disease of cattle, the wasting form, this one is manifested by delirious signs of circling, head pushing, leaning, straddling, forceful licking including themselves, salivation and incoordination. There is a strong acetonuria and odor on the breath.
autonomic nervous system
the branch of the nervous system that works without conscious control. The voluntary nervous system governs the striated or skeletal muscles, whereas the autonomic governs the glands, the cardiac muscle, and the smooth muscles, such as those of the digestive system, the respiratory system and the skin. The autonomic nervous system is divided into two subsidiary systems, the sympathetic system and the parasympathetic system.
It is also divided into central and peripheral sections. The core of the central section is the hypothalamus which receives afferent input from many other parts of the brain including the cerebral cortex. Its efferent output goes to many lower centers in the nervous system that have visceral control as their functions, e.g. the respiratory center in the medulla. The peripheral section consists of nonmedullated nerve fibers that leave the central nervous system in the craniosacral outflow (parasympathetic system) or the thoracolumbar outflow (sympathetic) system, and terminate in effector organs after passing through a ganglion, visible paravertebral ganglia in the sympathetic system, or ganglia embedded in the wall of the target organ in the parasympathetic system.
central nervous system
the portion of the nervous system consisting of the brain and spinal cord. See also nervous, brain, cerebral.
nervous dysfunction
can occur in any of four ways: (1) Excitation or irritation, an increase in the number of electrical stimuli or facilitation in their passage. (2) Release phenomena, from the damping, modifying effects of higher centers; includes spasticity, exaggerated tendon jerks. (3) paralysis, due to reduction or cessation of transmission of nerve impulses. (4) Nervous shock, a temporary cessation of activity in the nervous system as a whole in response to an insult applied to a part of it.
nervous excitation
see nervous dysfunction (above).
nervous paralysis
see nervous dysfunction (above).
peripheral nervous system
the portion of the nervous system consisting of the nerves and ganglia outside the brain and spinal cord.
nervous release phenomena
see nervous dysfunction (above).
nervous shock
see nervous dysfunction (above).
nervous system
the organ system that along with the endocrine system, correlates the adjustments and reactions of an organism to internal and environmental conditions, comprising the central, peripheral and autonomic nervous systems.