system /sys·tem/ (sis´tim)
Sympathetic nervous system
sympathetic nervous system.
sympathetic [sim″pah-thet´ik]
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. a school or method of practice based on a specific set of principles.
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.
| sympathetic nervous system n. The part of the autonomic nervous system originating in the thoracic and lumbar regions of the spinal cord that in general inhibits or opposes the physiological effects of the parasympathetic nervous system, as in tending to reduce digestive secretions or speed up the heart. |
Sympathetic nervous system
The part of the autonomic nervous system that is concerned especially with preparing the body to react to situations of stress or emergency; it contains chiefly adrenergic fibers and tends to depress secretion, decrease the tone and contractility of smooth muscle, and increase heart rate.
sympathetic nervous system.
sympathetic [sim″pah-thet´ik]
1. pertaining to or caused by sympathy.
2. pertaining to the sympathetic nervous system.
sympathetic nervous system 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. (See also Plate 14.)
sympathetic stress reaction alarm reaction.
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.
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.
sympathetic (sim´p
thet´ik),adj pertaining to the sympathetic nervous system.
sympathetic nervous system,
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,
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.
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.
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.
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.
venopressor mechanisms.
sympathetic
pertaining to the sympathetic nervous system.
acute sympathetic blockade
trauma to the cervical spinal cord may be associated with bradycardia and hypotension.
sympathetic chain
the sympathetic trunk whose ganglia suggest a chain of beads.
sympathetic cholinergic vasodilator fibers
a system of efferent dilator nerves distributed only to skeletal muscles; the existence of the system has been verified only in cats and dogs; in other species where it is not present vasodilation is achieved only by relaxation of vasoconstrictor tone.
sympathetic nerves
1. see sympathetic trunk (below).
2. any nerve of the sympathetic nervous system.
sympathetic nervous system
the part of the autonomic nervous system whose preganglionic fibers arise from cell bodies in the thoracic and lumbar segments of the spinal cord; postganglionic fibers are distributed to the heart, smooth muscle, and glands of the entire body.
sympathetic outflow
the preganglionic fibers from the nerve cells in the thoracolumbar cord.
sympathetic regurgitation
see neurotic regurgitation.
sympathetic trunk
two long ganglionated nerve strands, one on each side of the vertebral column, extending from the base of the skull to the coccyx.
sympathetic trunk ganglia
ganglia situated segmentally along the paired sympathetic trunks beside the vertebral bodies.
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