- 1. A collection of axons establishing a conduction route for nerve impulses from one group of nerve cells to another group or to an effector organ composed of muscle or gland cells. 2. Any sequence of chemical reactions leading from one compound to another; if taking place in living tissue, usually referred to as a biochemical p.- 4-aminobutyrate p. the p. that ultimately converts 4-aminobutyrate to succinate; succinate is then converted to α-ketoglutarate, via the tricarboxylic acid cycle, which is then acted upon by glutamate dehydrogenase; glutamate is then decarboxylated to reform 4-aminobutyrate; an important p. for those cells that make this neuroactive molecule. SYN: GABA p..- auditory p. neural paths and connections within the central nervous system, beginning at the organ of Corti hair cells, continuing along the eighth nerve, and terminating at the auditory cortex.- critical p. outline or diagram that documents the process of diagnosis or treatment deemed appropriate for a condition based on practice guidelines.- Embden-Meyerhof p. the anaerobic glycolytic p. by which d-glucose (most notably in muscle) is converted to lactic acid. Cf.:glycolysis. SYN: Embden-Meyerhof-Parnas p..- Entner-Douderoff p. a degradative p. for carbohydrates in certain microorganisms ( E.G., Pseudomonas sp.) that lack hexokinase, phosphofructokinase, and glyceraldehyde-3-phosphate dehydrogenase.- GABA p. SYN: 4-aminobutyrate p..- lacrimal p. [TA] a space between the closed lids and the eyeball through which the tears flow to the punctum lacrimale. SYN: rivus lacrimalis [TA], Ferrein canal.- mercapturic acid p. a glutathione-dependent p. for the detoxification of a number of compounds, including arene oxides; an S-substituted glutathione is formed and ultimately converted to a mercapturic acid (an S-substituted N-acetylated l-cysteine), which is excreted; the leukotrienes are believed to be degraded through this p..- pentose phosphate p. a secondary p. for the oxidation of d-glucose (not occurring in skeletal muscle), generating reducing power (NADPH) in the cytoplasm outside the mitochondria and synthesizing pentoses and a few other sugars. It also provides a means of converting pentoses and certain other sugars into intermediates of the glycolytic p.. It proceeds from d-glucose 6-phosphate to d-ribulose and d-ribose phosphates, thence (with d-xylulose 5-phosphate) to d-sedoheptulose 7-phosphate and d-glyceraldehyde 3-phosphate; carbon dioxide is released in the gluconate-ribulose step. In plants, it participates in the formation of d-glucose from carbon dioxide in the dark reactions of photosynthesis. This p. is defective in certain inherited diseases, e.g., glucose-6-phosphate dehydrogenase deficiency. SYN: Dickens shunt, hexose monophosphate p., hexose monophosphate shunt, pentose monophosphate shunt, pentose phosphate cycle, phosphogluconate p., Warburg-Dickens-Horecker shunt, Warburg-Lipmann-Dickens-Horecker shunt.- sorbitol p. a p. responsible for d-fructose formation from sorbitol; increases in activity as the glucose concentration rises in diabetes. SYN: polyol p..- ubiquitin-protease p. p. in which a small protein cofactor, ubiquitin, couples with protein substrate to catalyze proteolytic destruction by proteases; this p. is highly selective and tightly regulated and is responsible for protein degradation seen in muscle-wasting diseases.- visual p. neural paths and connections within the central nervous system, beginning with the retina and terminating in the occipital cortex.
* * *path·way 'path-.wā, 'pȧth- n1) a line of communication over interconnecting neurons extending from one organ or center to another also a network of interconnecting neurons along which a nerve impulse travels2) the sequence of usu. enzyme-catalyzed reactions by which one substance is converted into another <metabolic \pathways>
* * *path·way (pathґwa) 1. a course, especially one followed in the attainment of a specific end. Called also path. 2. the nerve structures through which an impulse passes between groups of nerve cells or between the central nervous system and an organ or muscle; see also tract. 3. metabolic p.
Medical dictionary. 2011.