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Renascent

renascent (rî-nàs¹ent, -nâ¹sent) To be born again; coming again into being; showing renewed growth or vigor.2

[from Latin renâscêns, renâscent-, to be born again.]

 

 

Respiration

respiration (rès´pe-râ¹shen), process by which an organism exchanges gases with its environment. The term commonly refers to the overall process by which oxygen is taken from the air and transported to the cells for the OXIDATION of organic molecules, while the products of oxidation, carbon dioxide and water, are returned to the environment. In single-celled organisms, gas exchange occurs directly. The cells lose their high concentration of carbon dioxide to the environment by simple diffusion, while the environment provides its higher concentration of oxygen to the cells, also by diffusion. In complex animals, where internal cells are distant from the external environment, respiratory systems facilitate the passage of gases to and from internal tissues. In plants, gas exchange occurs in the stomates, respiratory organs found mostly in leaves. In human beings and other vertebrates, gas exchange takes place in the LUNGS. In breathing—the mechanical procedure for getting air to and from the lungs—muscles enlarge the chest cavity to force air in and reduce it to expel air. Actual gas exchange in the lungs occurs in cup-shaped air sacs called alveoli. Organisms that utilize respiration to obtain energy are aerobic, or oxygen-dependent. Organisms able to live in the absence of oxygen are called anaerobic; they obtain energy from fuel molecules solely by FERMENTATION or GLYCOLYSIS. In biochemistry, respiration refers to the series of biochemical oxidations in which organic molecules—such as carbohydrates, amino acids, and fatty acids—are converted to carbon dioxide and water. The chemical energy thus obtained is trapped and stored for later use by the cells in ADENOSINE TRIPHOSPHATE (ATP). 1

 

 

Rheumatoid arthritis

rheumatoid arthritis noun A chronic disease marked by stiffness and inflammation of the joints, weakness, loss of mobility, and deformity.2

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Serotonin

se·ro·to·nin (sèr´e-to¹nîn, sîr´-) noun An organic compound, C10H12N2O, formed from tryptophan and found in animal and human tissue, especially the brain, blood serum, and gastric mucous membranes, and active in vasoconstriction, stimulation of the smooth muscles, transmission of impulses between nerve cells, and regulation of cyclic body processes. [SERO- + TON(E) + -IN.] 2

 

 

Steroid

steroid, any of class of LIPIDS having a molecular structure based on four joined carbon rings with hydrogen molecules attached. Steroids differ from one another only in the additional atoms attached to the central structure. Many steroids are biologically active HORMONES. The class includes the sex hormones TESTOSTERONE, ESTROGEN, and PROGESTERONE, corticosteroids such as CORTISONE, several forms of vitamin D, CHOLESTEROL, and the BILE acids. Steroids are used in oral contraceptives and in the treatment of ARTHRITIS, ADDISON'S DISEASE, and certain skin ailments. ANABOLIC STEROIDS have been abused by bodybuilders and athletes in an attempt to increase muscle mass and strength. Steroids are found in plants and invertebrates as well as in vertebrates.1

 

Substantia nigra

substantia ni·gra (nì¹gre, nîg¹re) noun A layer of large, pigmented nerve cells in the mesencephalon that produce dopamine and whose destruction is associated with Parkinson's disease. [New Latin : Latin substantia, substance + Latin nigra, feminine of niger, black.] 2