| renin-angiotensin system | <physiology> A system consisting of renin, angiotensin-converting enzyme, and angiotensin II. Renin, an enzyme produced in the kidney, acts on angiotensinogen, an alpha-2 globulin produced by the liver, forming angiotensin I. The converting enzyme contained in the lung acts on angiotensin I in the plasma converting it to angiotensin II, the most powerful directly pressor substance known. It causes contraction of the arteriolar smooth muscle and has other indirect actions mediated through the adrenal cortex. (25 Jun 1999) |
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| centimeter-gram-second system | The scientific system of expressing the fundamental physical units of length, mass, and time, and those units derived from them, in centimeters, grams, and seconds; currently being replaced by the International System of Units based on the meter, kilogram, and second. (05 Mar 2000) |
| reproductive system | In women, the organs that are directly involved in producing eggs and in conceiving and carrying babies. (12 Dec 1998) |
| pedal system | Efferent fibres connecting the forebrain with more caudal structures. (05 Mar 2000) |
| 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) |
| glycogen debranching enzyme system | 1,4-alpha-d-glucan-1,4-alpha-d-glucan 4-alpha-d-glucosyltransferase/dextrin 6 alpha-d-glucanohydrolase. An enzyme system having both 4-alpha-glucanotransferase (ec 2.4.1.25) and amylo-1,6-glucosidase (ec 3.2.1.33) activities. As a transferase it transfers a segment of a 1,4-alpha-d-glucan to a new 4-position in an acceptor, which may be glucose or another 1,4-alpha-d-glucan. As a glucosidase it catalyses the endohydrolysis of 1,6-alpha-d-glucoside linkages at points of branching in chains of 1,4-linked alpha-d-glucose residues. Amylo-1,6-glucosidase activity is deficient in glycogen storage disease type III. (12 Dec 1998) |
| respiratory system | The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs. (12 Dec 1998) |
| respiratory system abnormalities | Congenital structural abnormalities of the respiratory system. (12 Dec 1998) |
| respiratory system agents | Drugs used for their effects on the respiratory system. (12 Dec 1998) |
| reticular activating system | <physiology> A physiological term denoting that part of the brainstem reticular formation that plays a central role in the organism's bodily and behavorial alertness. It extends as a diffusely organised neural apparatus through the central region of the brainstem into the subthalamus and the intralaminar nuclei of the thalamus; by its ascending connections it affects the function of the cerebral cortex in the sense of behavioural responsiveness; its descending (reticulospinal) connections transmit its activating influence upon bodily posture and reflex mechanisms (e.g., muscle tonus), in part by way of the gamma motor neurons. See: reticular formation. Synonym: non-specific system. (05 Mar 2000) |