autonomic nervous system (redirected from Sympathetic fibers)

system /sys·tem/ (sis´tim)

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. a school or method of practice based on a specific set of principles.

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alimentary system  digestive s.

auditory system  the series of structures by which sounds are received from the environment and conveyed as signals to the central nervous system; it consists of the outer, middle, and inner ear and the tracts in the auditory pathways.

autonomic nervous system  the portion of the nervous system concerned with regulation of activity of cardiac muscle, smooth muscle, and glands, usually restricted to the sympathetic and parasympathetic nervous systems.

Bethesda System  a classification of cervical and vaginal cytology used in cytopathologic diagnosis.

cardiovascular system  the heart and blood vessels, by which blood is pumped and circulated through the body.

CD system  [c luster d esignation] a system for classifying cell surface markers expressed by lymphocytes based on a computer analysis grouping similar monoclonal antibodies raised against human leukocyte antigens.

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  (CNS) the brain and spinal cord.

centrencephalic system  the neurons in the central core of the brain stem from the thalamus to the medulla oblongata, connecting the two hemispheres.

chromaffin system  the chromaffin cells of the body considered collectively.

circulatory system  channels through which nutrient fluids of the body flow; often restricted to the vessels conveying blood.

colloid system , colloidal system see colloid (2).

conduction system of heart  a system of specialized muscle fibers that generate and transmit cardiac impulses and coordinate contractions, comprising the sinoatrial and atrioventricular nodes, bundle of His and its bundle branches, and subendocardial branches of Purkinje fibers.

digestive system  the organs concerned with ingestion, digestion, and absorption of food or nutritional elements.

endocrine system  the glands and other structures that elaborate and secrete hormones that are released directly into the circulatory system, influencing metabolism and other body processes; included are the pituitary, thyroid, parathyroid, and adrenal glands, pineal body, gonads, pancreas, and paraganglia.

enteric nervous system  the enteric plexus, sometimes considered separately from the autonomic nervous system because it has independent local reflex activity.

extrapyramidal system  a functional, rather than anatomical, unit comprising the nuclei and fibers (excluding those of the pyramidal tract) involved in motor activities; they control and coordinate especially the postural, static, supporting, and locomotor mechanisms. It includes the corpus striatum, subthalamic nucleus, substantia nigra, and red nucleus, along with their interconnections with the reticular formation, cerebellum, and cerebrum.

genitourinary system  urogenital s.

haversian system  a haversian canal and its concentrically arranged lamellae, constituting the basic unit of structure in compact bone (osteon).

heterogeneous system  a system or structure made up of mechanically separable parts, as an emulsion or a suspension.

His-Purkinje system  a portion of the conducting system of the heart, usually referring specifically to the segment beginning with the bundle of His and ending at the terminus of the Purkinje fiber network within the ventricles.

homogeneous system  a system or structure made up of parts which cannot be mechanically separated, as a solution.

hypophysioportal system , hypothalamo-hypophysial portal system the venules connecting the capillaries (gomitoli) in the median eminence of the hypothalamus with the sinusoidal capillaries of the adenohypophysis.

immune system  a complex system of cellular and molecular components having the primary functions of distinguishing self from not self and of defense against foreign organisms or substances.

International System of Units  see SI unit, under unit.

keratinizing system  the cells composing the bulk of the epithelium of the epidermis, which are of ectodermal origin and undergo keratinization and form the dead superficial layers of the skin.

limbic system  a group of brain structures (including the hippocampus, gyrus fornicatus, and amygdala) common to all mammals; it is associated with olfaction, autonomic functions, and certain aspects of emotion and behavior.

locomotor system  the structures in a living organism responsible for locomotion, in humans consisting of the muscles, joints, and ligaments of the lower limbs as well as the arteries and nerves that supply them.

lymphatic system  the lymphatic vessels and lymphoid tissue, considered collectively.

lymphoid system  the lymphoid tissue of the body, collectively; it consists of (a) a central component, including the bone marrow, thymus, and an unidentified portion called bursal equivalent tissue; and (b) a peripheral component consisting of lymph nodes, spleen, and gut-associated lymphoid tissue (tonsils, Peyer's patches).

lymphoreticular system  the tissues of the lymphoid and reticuloendothelial systems considered together as one system.

masticatory system  the bony and soft structures of the face and mouth involved in mastication, and the vessels and nerves supplying them.

metric system  a decimal system of weights and measures based on the meter.

mononuclear phagocyte system  (MPS) the set of cells consisting of macrophages and their precursors (blood monocytes and their precursor cells in bone marrow). The term has been proposed to replace reticuloendothelial system, which does not include all macrophages and does include other unrelated cell types.

muscular system  the muscles of the body considered collectively; generally restricted to the voluntary, skeletal muscles.

nervous system  the organ system which, along with the endocrine system, correlates the adjustments and reactions of the organism to its internal and external environment, comprising the central and peripheral nervous systems.

parasympathetic nervous system  the craniosacral portion of the autonomic nervous system, its preganglionic fibers traveling with cranial nerves III, VII, IX, X, and XI, and with the second to fourth sacral ventral roots; it innervates the heart, smooth muscle and glands of the head and neck, and thoracic, abdominal, and pelvic viscera.

peripheral nervous system  all elements of the nervous system (nerves and ganglia) outside the brain and spinal cord.

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 and liver.

Purkinje system  a portion of the conducting system of the heart, usually referring specifically to the Purkinje network.

respiratory system  respiratory tract; the tubular and cavernous organs that allow atmospheric air to reach the membranes across which gases are exchanged with the blood.

reticular activating system  the system of cells of the reticular formation of the medulla oblongata that receive collaterals from the ascending sensory pathways and project to higher centers; they control the overall degree of central nervous system activity, including wakefulness, attentiveness, and sleep; abbreviated RAS.

reticuloendothelial system  (RES) a group of cells having the ability to take up and sequester inert particles and vital dyes, including macrophages and macrophage precursors, specialized endothelial cells lining the sinusoids of the liver, spleen, and bone marrow, and reticular cells of lymphatic tissue (macrophages) and bone marrow (fibroblasts). See also mononuclear phagocyte s.

SI system  see under unit.

stomatognathic system  structures of the mouth and jaws, considered collectively, as they subserve the functions of mastication, deglutition, respiration, and speech.

sympathetic nervous system  (SNS) the thoracolumbar part of the autonomic nervous system, the preganglionic fibers of which arise from cell bodies in the thoracic and first three lumbar segments of the spinal cord; postganglionic fibers are distributed to the heart, smooth muscle, and glands of the entire body.

urinary system  the organs and passageways concerned with the production and excretion of urine, including the kidneys, ureters, urinary bladder, and urethra.

urogenital system  the urinary system considered together with the organs of reproduction.

vascular system  circulatory s.

visual system  the series of structures by which visual sensations are received from the environment and conveyed as signals to the central nervous system; it consists of the photoreceptors in the retina and the afferent fibers in the optic nerve, chiasm, and tract.

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autonomic nervous system

n.

The part of the nervous system that regulates involuntary action, as of the intestines, smooth muscle, heart, and glands, and that is divided into two physiologically and anatomically distinct, mutually antagonistic systems, the sympathetic nervous system and the parasympathetic nervous system.

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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.

Mentioned in: Anxiety, Biofeedback, Dizziness, Guided Imagery, Shy-Drager Syndrome, Spinal Cord Injury

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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.

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

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

Autonomic nervous system.

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autonomic,

n See autonomic nervous system.

autonomic drugs,

n agents that act on the autonomic nervous system.

autonomic dysreflexia/hyperreflexia

n an emergent, typically life-threatening, medical condition resulting from a dramatic increase in blood pressure occurring in individuals with traumatic lesions at or above T6. Symptoms may include a throbbing headache, blushing, chills, sweating, stuffy nose, and fidgetiness.

autonomic nervous system (ANS),

n a subdivision of the efferent peripheral nervous system that regulates involuntary vital function, including the activity of the cardiac muscle, the smooth muscle, and the glands. Has two parts: the sympathetic nervous system, which accelerates heart rate, constricts blood vessels, and raises blood pressure; and the parasympathetic nervous system, which slows heart rate, increases intestinal peristalsis and gland activity, and relaxes sphincters. See also peripheral nervous system.

autonomic nervous system, fibers of, in pulp,

n.pl the nerve fibers of the sympathetic autonomic system that enter the pulp tissue and function in regulating blood flow.

autonomic symptoms,

n the indications of pathology or trauma, including paleness, sweating, blushing, dilation of pupils, irregular cardiac rhythm, and lack of bladder control.

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system,

n a set or series of organs or parts that unite in a common function.

system, acid-base buffer,

n the system by which a virtually constant pH level of the blood and body fluids is maintained. The base and acid electrolytes associated with normal metabolism are continuously introduced into the bloodstream. Notwithstanding the marked amounts of base or acid or both introduced into the bloodstream during exercise, rest, hunger, or the ingestion of fluid and solid foods, the pH level of the blood remains rather constant between 7.3 and 7.5. Four means by which this relatively narrow but constant pH level is maintained are: the buffer system of the blood, tissue and cell fluids, and mineral salts of the bone matrix; excretion and retention of carbon dioxide by the lungs; excretion of an acid or alkaline urine; and the formation or excretion of ammonia and organic compounds.

system, apothecaries'

n a nondecimal system of weights and measures traditionally used by druggists. See also system, avoirdupois.

system, autonomic nervous,

n See autonomic nervous system (ANS).

system, avoirdupois

n a commercial nondecimal system of weights and measures. See also system, apothecaries'.

system, central nervous (CNS),

n the brain and spinal cord, including their nerves and end organs; controls all voluntary acts.

system, circulatory,

n the heart and blood vessels. Three major groups of blood vessels are defined: arteries, capillaries, and veins. The system transports metabolites to and from the tissue cells.

system, computer,

n an assembly of procedures, processes, methods, routines, techniques, and equipment united by some form of regulated interaction to form an organized whole. It is an approach to a complex problem.

system, flowchart,

n a pictorial diagram illustrating the flow of information into, through, and out of a system of programs.

system, hematopoietic

n a term used to describe collectively the blood, bone marrow, lymph nodes, spleen, and reticuloendothelial cells.

system, masticatory,

n the organs and structures primarily functioning in mastication: the jaws, teeth, and their supporting structures; temporomandibular articulation; mandibular musculature; tongue; lips; cheeks; and oral mucosa and their nerve supplies.

system, metric,

n a decimal system of weights and measures almost universally used in scientific and professional work, including the writing of prescriptions. The individual units are based on an international set of standards, notably the meter, liter, and kilogram. In dentistry, measurement is done by the metric system.

system, musculoskeletal,

n the system of body structures that provides the energy and movement necessary for the functions of life. The muscles, bones, and connective tissues of the body are grouped together into one system, and they are intimately connected in their individual and combined functions. E.g., for muscle to accomplish its ultimate purpose of movement by contraction, bone, leverage, and connective tissue are required to transmit the force that the contraction generates. In the oral cavity and its related structures the musculoskeletal tissues fulfill the mechanical and structural requirements for movement of the mandible and some related visceral functions, such as respiration and digestion.

system, neurohormonal,

n the system by which the hormone secretions of the endocrine glands function in part as the regulators of both visceral and somatic function and have intimate anatomic and functional relationships with the nervous system by the union of the pituitary gland and the hypothalamus of the cerebrum. The pituitary gland has a pars nervosa, which is an extension of the anterior part of the hypothalamus, and a pars intermedia, which is an epithelial evagination of the secretory tissue from the stomodeum of the embryo. From its position in the cranial structures in the sella turcica, the pituitary gland regulates, by its union with the nervous system, the whole endocrine system, with its many glands; these glands in turn partially regulate the viscera and somatic muscle organs.

system, occlusal (occlusal scheme),

n the form or design and arrangement of the occlusal and incisal units of a dentition or of the teeth on a denture. See also system, masticatory.

system, parasympathetic nervous,

n one of the motor divisions of the autonomic nervous system. It is described as the
craniosacral division and does not have the simplified structural apparatus of the strong sympathetic adrenal axis about which to function. It inhibits the heart, contracts the pupils, and, in emotional states, produces a vagus-insulin axis of activity. The several parts function rather independently. The ocular division relates to the midbrain, and the bulbar division relates to the hindbrain. The bulbar division supplies the facial, glossopharyngeal, and vagus nerves. It also supplies the secretory and vasodilator fibers of the salivary glands and mucous membranes of the oral cavity and pharynx. In conditions of very loud noise or unusual anxiety states, the parasympathetic system causes unaccounted-for spontaneous urination, excessive salivary and gastric juices, and either nausea or vomiting.

system, proaccelerin-accelerin,

n See factor V.

system, proconvertin-convertin,

n See factor VII.

system, stomatognathic,

n the combination of all the structures involved in speech and the reception, mastication, and deglutition of food. The system is composed of the teeth, jaws, muscles of mastication, epithelium, and temporomandibular joints and nerves that control these structures.

system, sympathetic nervous,

n one of the two opposing motor systems in the autonomic nervous system that mediate the activity of the viscera. (The other is the
parasympathetic system.) It is composed of 21 or 22 ganglia in chains on each side of the spinal cord. The fibers connect with the spinal cord through these ganglia. The actions are closely allied to the action of the medulla of the adrenal gland; thus a sympathetic-adrenal axis that functions as a unit to protect and regulate the body environment may be conceived. The sympathetic control is modified by the volitional somatic control of the patient. The volitional control, superimposed on the autonomic control, gives rise to great variations in motor patterns, as seen in the face in the presence of emotional changes, such as in the blushing of shame and pallor of fear.

system, vascular, closed tube,

n the type of vascular system, as in humans, in which the blood circulates through the vessels (or tubes) and is not dissipated into the tissues. The closed vascular tube system offers resistance to the pumping action of the heart because the pressures are cumulative with each pumping action. The elastic walls in the arterial vessels, particularly in the aorta, absorb the additional energy and release it slowly, thus creating the possibility of maintaining a fairly steady and safe pressure head throughout the vascular system. The high-pressure point at the height of cardiac contraction is the
systole, and the low point before the ventricular contraction is the
diastole.

system, vascular, open tube,

n in some vertebrates a vascular system with an open end that causes the blood fluid to dissipate into the tissues. This system starts with a maximal head pressure that diminishes until inertia in the blood is overcome. The blood is returned to the heart by muscle function, gravity, and diffusion. The blood pressure in this system fluctuates from a maximum at the heart to a minimum at the tissue cell.

system, venous,

n a system of interconnected blood vessels that returns blood to the heart from the tissue and capillary bed through progressively larger vessels. The following affect the return of blood to the heart: thoracic pressure, associated with respiration; gravity, associated with body posture; the valves, diameter of the lumen, and muscle structure of the veins; muscle contraction of the somatic structures; the pressures in the arteriole system and capillary bed; and the nervous and hormonal system controls that regulate cardiomuscular activity. The influences over the venous system circulation are collectively termed
venopressor mechanisms.

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autonomic

not subject to voluntary control.

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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.

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nervous

1. pertaining to a nerve or nerves.

2. unduly excitable.

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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.