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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.
See also: apparatus, classification.
See also: apparatus, classification.
See also: apparatus, classification.
People, hardware, software, applications and/or methods organised to accomplish a set of specific functions or objectives.
systemA defined collection of related structures and processes and the components required for their function. See ABO system, Admission-discharge-transfer system, Adrenergic system, Aldrete Recovery Room Scoring system, All-payer system, Allocation system, Alternate delivery system, Auditory system, Autonomic nervous system, Barotypic system, Bartenieff fundamentals system, Beta-Cath system, Bethesda system, BioLogic-HT™ system, BioZ system, Bonus system, Buddy system, Central nervous system, CHARS, CHESS system, Circulatory system, Clinical laboratory information management system, Closed system, Closed loop system, Community support system, Community water system, Computer-assisted diagnostic system, Computerized thermal imaging system, Conduction system, Consecutive water system, Cotswolds Staging system, DBx diagnostic system, Decision support system, Digestive system, Disease simulation system, Distribution system, Dual review system, Dynamic system, Early warning system, Eclipse system, Enterprise liability system, Er:YAG laser system, Executive information system, Expert system, Expression system, Extrapyramidal system, Feedback system, FIGO staging system, Fluoridated water system, Fountain™ system, Freehand system, Genitourinary system, Geographic information system, Gleason grading system, Global positioning system, Graham system, Groundwater system, Hamilton score system, Hepatic portal system, Hospital information system, HCPCS system, Humoral immune system, Immune, system, Incardia CABG system, Incardia valve system, Individual water system, Injury Surveillance system, Integrated delivery system, Kallikrein-kinin system, Laboratory information system, Lane system, Legacy system, Lewis system, Limbic system, Linear system, Lymphatic system, Lyophilized liposomal delivery system, Magnocellular system, Management information system, Medical anthrotonic system, Medication Event Monitoring system, Medipatch™ system, MICRO21 automated microscope system, MIDCAB™ system, Mirizzi system, Mission-critical system, MLR system, Model system, Mononuclear phagocytic system, Morter HealthSystem, Mossy fiber system, Mountain staging system, Multiaxial system, Multipayer system, Multiple chemical sensitivities system, NADPH oxidase system, National Health system, Natural-Hip system, Natural-Knee system, Naturally fluoridated water system, Nervous system, Neuroendocrine system, Noncommunity water system, Nonlinear system, Open protocol system, Nontransient system, Operating system, Opioid-mediated analgesia system, OSCAR system, PACS system, Papile system, Parvocellular system, Patient accounting system, Pedicle screw fixation system, Pluralistic system, Pneumatic tube system, Prognostic scoring system, Prospective payment system, Prostar system, Public water system, Pyramid system, Quartet™ system, Quinton® Synergy™ cardiac information management system, RAI staging system, Read classification system, Red system, r/LS system, Remote Automated Laboratory system, Renin-angiotensin-aldosterone system, Reproductive system, Respiratory system, Revelation™ hip system, Rh system, Rosenkranz™ pediatric retractor system, Rye Staging system, Sabolich socket system, SalEst™ system, School water system, Second messenger system, Sentinel™ 2010 implantable cardioverter-defibrillator system, Sharplan™ SilkTouch laser system, Side Branch Occlusion system, Silhouette laser system, Simal cervical stabilization system, Single-payer system, SkinLaser™ system, Skinlight erbium-YAG laser system, SomnoplastySM system, Sonic accelerated fracture healing system, Static system, Station system, Stress system, Subsystem, Svennerholm system, Sydney system, Sympathetic nervous system, Television rating system, Thermochemic HT™ system, Thermoflex™ system, Thoratec® VAD system, Tort system, Total hip system, Total knee system, Trusted system, Two-tiered system, Unified health care system, Vacuum system, Vestibular system, Voluntary Resident Tracking system, Walter Reed Staging system, Withhold system.
Synonym(s): systema [TA] .
systemA group of related organs that act together to perform a common function. Body systems include the digestive system, the respiratory system, the cardiovascular system, the urinary system and the reproductive system.
autonomic nervous system (ANS) A part of the nervous system involved in the regulation of the internal environment (homeostasis) which is achieved mostly by controlling cardiovascular, digestive, respiratory and reproductive functions of the body, as well as salivation, perspiration, pupil size, urinary and genital systems. Most of these activities are involuntary, although, for example, breathing can be partly voluntary. Sensory information from the visceral sensory neurons (afferent) located in the peripheral nervous system (PNS), such as monitoring the composition of the blood and stomach, is conveyed to the central nervous system (CNS), especially the hypothalamus and medulla oblongata, where it is integrated. Motor neurons (efferent) of the ANS consist of a set of two neurons: the first with its cell body in the CNS project to an autonomic ganglion (preganglionic neuron) and a second motor neuron (postganglionic neuron) outside the CNS, innervates visceral effectors (target organs). The efferent part of the ANS has two principal divisions: sympathetic and parasympathetic. Many organs receive autonomic fibres from both divisions. The preganglionic sympathetic neurons have their cell bodies in the lateral horn and the first two or three lumbar segments of the spinal cord, while the parasympathetic preganglionic neurons are found in the brainstem and their axons leave the brain via the third, seventh, ninth and tenth cranial nerves. Sympathetic postganglionic neurons project to sympathetic ganglia from which axons project to the eyes, lacrimal glands, salivary glands, respiratory, cardiovascular, digestive, urinary and reproductive systems. Parasympathetic postganglionic neurons are located in or near the target organs. They also innervate the eyes, lacrimal glands, salivary glands, respiratory, cardiovascular, digestive systems, urinary and reproductive systems. Examples: sympathetic stimulation causes pupil dilatation and relaxation of the ciliary muscle, while parasympathetic stimulation causes pupil constriction, accommodation and lacrimal secretion.The
sympathetic nervous system dominates in stressful situations causing a 'fight or flight' response, while the parasympathetic nervous system primarily regulates those activities that conserve and restore energy. Acetylcholine is the neurotransmitter for sympathetic and parasympathetic preganglionic neurons and for postganglionic parasympathetic neurons, which act on muscarinic receptors, while noradrenaline (norepinephrine) is the neurotransmitter for all postganglionic sympathetic neurons (except for the sweat glands) which act on adrenergic receptors. See acetylcholine; adrenergic receptors.
boxing system A method of measurement of the eyesize of spectacle frames. It is based on a rectangle with its horizontal and vertical length tangential to the edges of the lens. The horizontal lens size is equal to the horizontal length of the rectangle. Syn. box system of lens measurement; boxing method. See boxing centre; standard optical position centre.
catadioptric system An optical system employing both reflecting and refracting components as used, for example, in a lighthouse. This design makes long focal length more compact and mirrors, unlike lenses or prisms, are free of chromatic aberration. See catadioptric image.
central nervous system (CNS) The largest part of the nervous system, comprising the brain and the spinal cord. The brain is encased and protected by the skull and the spinal cord by the vertebrae, as well as the meninges and the blood-brain barrier that protects against blood-borne toxins. The central nervous system processes and integrates sensory information received from the peripheral nervous system and issues appropriate motor responses.
centred optical system See optical system.
compound optical system An optical system consisting of more than one lens (e.g. the eyepiece of a telescope).
immune system A complex system that protects the body against infection, disease and malignant cells by producing the immune response. The system includes skin and mucous secretions, white blood cells (leukocytes), lymphocytes (B cells and T cells), killer T cells, complement system (proteins in the blood) and antibodies. Disorders of the immune system can cause disease: they include immunodeficiencies due to aging, alcoholism, malnutrition, etc., immune responses against its own cells (autoimmunity), or damaging effects caused by the immune system (hypersensitivity). See autoimmune disease; hypersensitivity.
magnocellular visual system That part of the visual pathway from the photoreceptors in the retina to layer 4Cα (and to a lesser extent in layer 6) of the visual cortex and then projected to area V5, which is mainly responsible for transmitting information about movement, depth perception and high contrast targets. Action potentials are transmitted faster in this pathway because of the large diameter axons of these neurons than in the parvocellular pathway. Syn. dorsal stream; parietal pathway; transient visual system; 'where' system. See M cell; dyslexia; lateral geniculate bodies; two visual systems theory.
optical system A collection of lenses, prisms, mirrors, etc. which act together to produce an image of an external object. If the axes of all the components coincide, the system is called a centred optical system.
parvocellular visual system That part of the visual pathway from the photoreceptors in the retina to layer 4Cβ, (and to a lesser extent in layers 4A and 6) of the primary visual cortex and then projected to area V4, which is mainly responsible for transmitting information about visual acuity, form vision, colour vision and low contrast targets. Syn. sustained visual system; ventral stream; 'what' system. See visual association areas; ganglion cell; P cell; lateral geniculate bodies; two visual systems theory.
peripheral nervous system (PNS) The part of the nervous system which consists of the nerves and neurons that are outside the brain and spinal cord. It comprises the cranial nerves, spinal nerves and the autonomic nervous system. The primary role of the peripheral nervous system is to transmit sensory information about the external and internal milieus to the central nervous system and to transmit motor commands to the effectors such as muscles and glands. Note: some authors do not consider the autonomic nervous system as part of the peripheral nervous system. It is, however, a separate entity, which is part central and part peripheral.
'what' system See parvocellular visual system.
'where' system See magnocellular visual system.
Patient discussion about system
Q. Is fibromyalgia related to Central Nervous System? Is fibromyalgia related to Central Nervous System? Among men and women who is more prone to the symptoms of fibromyalgia?
"Little research has been conducted that measures the prevalence of fibromyalgia, and estimates vary widely as to the proportion of male versus female patients. A 1999 epidemiology study conducted in London found a female to male ratio of roughly three to one. However, a 2001 review of the research literature in Current Rheumatology Reports stated the ratio was nine to one."
Q. on what systems does ADHD effects?
Q. on what system in the body does a Fibromyalgia effects?