| parasympathetic nervous system | <anatomy, neurology> One of the two divisions of the vertebrate autonomic nervous sytem. Parasympathetic nerves emerge cranially as pre ganglionic fibres from oculomotor, facial, glossopharyngeal and vagus and from the sacral region of the spinal cord. most neurons are cholinergic and responses are mediated by muscarinic receptors. The parasympathetic system innervates, for example: salivary glands, thoracic and abdominal viscera, bladder and genitalia. Compare:. Sympathetic nervous system. (18 Nov 1997) |
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| visceral nervous system | <anatomy> Neurons that are not under conscious control, comprising two antagonistic components, the sympathetic and parasympathetic nervous systems. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: 1. The sympathetic nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure. 2. The parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. (03 Jul 1999) |
| central nervous system | <anatomy, neurology> Pertaining to the brain, cranial nerves and spinal cord. It does not include muscles or peripheral nerves. In invertebrates, the central nervous system is composed of the segmental ganglia of the ventral nerve cord together with the fused ganglia or brain at the anterior end. Acronym: CNS (12 Jan 1998) |
| central nervous system agents | A class of drugs producing both physiological and psychological effects through a variety of mechanisms. They can be divided into "specific" agents, e.g., affecting an identifiable molecular mechanism unique to target cells bearing receptors for that agent, and "non-specific" agents, those producing effects on different target cells and acting by diverse molecular mechanisms. Those with non-specific mechanisms are generally further classed according to whether they produce behavioural depression or stimulation. Those with specific mechanisms are classed by locus of action or specific therapeutic use. (12 Dec 1998) |
| central nervous system depressants | A very loosely defined group of drugs that tend to reduce the activity of the central nervous system. The major groups included here are ethyl alcohol, anaesthetics, hypnotics and sedatives, narcotics, and tranquillising agents (antipsychotics and antianxiety agents). (12 Dec 1998) |
| central nervous system infections | Diseases of the central nervous sytem collectively, caused by pathogenic organisms. (12 Dec 1998) |
| central nervous system neoplasms | Neoplasms located in the brain, spinal cord, or meninges. (12 Dec 1998) |
| central nervous system stimulants | A loosely defined group of drugs that tend to increase behavioural alertness, agitation, or excitation. They work by a variety of mechanisms, but usually not by direct excitation of neurons. The many drugs that have such actions as side effects to their main therapeutic use are not included here. (12 Dec 1998) |
| peripheral nervous system | One of the two major divisions of the nervous system. Nerves in the PNS connect the central nervous system (CNS) with sensory organs, other organs, muscles, bloodvessels and glands. (22 May 1997) |
| peripheral nervous system agents | Drugs that act principally at one or more sites within the peripheral neuroeffector systems, the autonomic system, and motor nerve-skeletal system. (12 Dec 1998) |
| peripheral nervous system diseases | Diseases of the peripheral nervous system, including disorders of the peripheral autonomic system, the cranial nerves, and the spinal nerves and roots, but not including neuromuscular and spinal cord diseases. (12 Dec 1998) |
| metameric nervous system | That part of the nervous system which innervates body structures developed in ontogeny from the segmentally arranged somites or, in the head region, branchial arches. The term implies reference to the neural mechanisms intrinsic to the spinal cord and brainstem (represented by the sensory nuclei, motoneuronal cell groups, and their associated interneurons in the reticular formation); by strict definition it should exclude the autonomic nervous system. (05 Mar 2000) |
| coeliac (nervous) plexus | The most substantial, superior portion of the abdominal aortic plexus lying anterior to the aorta at the level of origin of the coeliac trunk (vertebral level T-12); the coeliac ganglia lie within the plexus; it is formed by contributions from the greater splanchnic and vagus (especially the posterior or right vagus) nerves and communicating branches to and from the superior mesenteric and renal plexuses and ganglia; most sympathetic, parasympathetic and visceral afferent fibres serving the abdominal viscera pass through this plexus. Synonym: plexus coeliacus, solar plexus. (05 Mar 2000) |
| Henle's nervous layer | The layers of the retina from the outer plexiform to the nerve fibre layer inclusive. Synonym: Henle's nervous layer. (05 Mar 2000) |
| high pressure nervous syndrome | <syndrome> A syndrome of tremors, nausea, dizziness, and decreased motor and mental performance which develops in those who dive deeply (c. 1000 ft) usually breathing a mixture of oxygen and helium. Nitrogen is not a factor as it is in inert gas narcosis. (12 Dec 1998) |