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- A -
- Acetic Acid
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- acetic acid A clear, colorless organic acid, CH3COOH, with
a distinctive pungent odor 1
- Acetylcholine
- acetylcholine (e-sêt´l-ko¹lên´), organic compound containing
carbon, hydrogen, oxygen, and nitrogen, essential for the conduction of nerve impulses in
animals. It is found in highest concentrations on neuron surfaces and is liberated at
nerve cell endings. There is strong evidence that acetylcholine is the transmitter
substance that conducts impulses from one cell to another in the parasympathetic nervous
system, and from nerve cells to smooth muscle, skeletal muscle, and exocrine glands. 1
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- Adenosine Triphosphate or ATP
- adenosine triphosphate, (ATP), organic compound composed of
adenine, ribose, and three phosphate units. ATP serves as the major energy source within
cells, driving such biological processes as photosynthesis, muscle contraction, and
protein synthesis. It is broken down by hydrolysis (reaction with water) to yield
adenosine diphosphate (ADP), inorganic phosphorus, and energy. ADP can be further broken
down by hydrolysis to yield adenosine monophosphate (AMP), inorganic phosphorus, and
energy. Excess phosphorus yielded from these and subsequent reactions is used to produce
new ATP from AMP. 1
- Adrenaline or Epinephrine
- epinephrine (èp´e-nèf¹rîn) or adrenaline
(e-drèn¹e-lîn), hormone secreted by the medulla of the ADRENAL GLANDS. Strong emotions,
such as fear and anger, cause epinephrine to be released into the bloodstream, producing
an increase in heart rate, muscle strength, blood pressure, and sugar metabolism. This
reaction, often called the "fight or flight" response, prepares the body for
strenuous activity. In medicine, epinephrine is used chiefly as a stimulant in cardiac
arrest, as a vasoconstrictor in shock, and as a bronchodilator and antispasmodic in
bronchial asthma. See also CATECHOLAMINE.
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- Aldosterone
- al·dos·ter·one (àl-dòs¹te-ron´) noun A hormone
secreted by the adrenal cortex that regulates the salt and water balance in the body. This
is a steroid hormone. [ALD(EHYDE) + STER(OL) + -ONE.] 2
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- Alzheimer’s Disease
- Alzheimer’s disease (älts¹hì-merz), degenerative disease
of the brain cells producing loss of memory and general intellectual impairment. It
usually affects people over age 65, although it can appear earlier, especially in some
familial forms of the disease. As the disease progresses, a variety of symptoms may become
apparent, including confusion, irritability, and restlessness, as well as disorientation
and impaired judgment and concentration. The cause is unknown, although there appears to
be a genetic component; the excessive beta amyloid proteins and the traces of aluminum
found in the brains of victims are being studied as possible contributors. There is no
cure, but the drug tacrine provides temporary improvement for some patients. 1
Alz·heim·er’s disease (älts¹hì-merz, àlts¹-, ôlts¹-, ôlz¹hì-mers)
noun A disease marked by progressive loss of mental capacity resulting from degeneration
of the brain cells. [After Alois Alzheimer (1864-1915), German neurologist.] 2-
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- Amyotrophic Lateral Sclerosis
- amyotrophic lateral sclerosis, (ALS), degenerative disease that affects nerve
cells in the brain and spinal cord, preventing them from sending impulses to the muscles.
The muscles atrophy quickly, causing weakness, paralysis, and eventual death. About half
of the inherited cases are caused by a gene mutation on chromosome 21. Lou GEHRIG died of
the disease in 1941, bringing it national attention.1
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- Antioxidant
- antioxidant, substance that prevents or slows OXIDATION.
Antioxidants are used as FOOD ADDITIVES to retard spoilage and color changes. Studies show
that antioxidants in the body, such as vitamins E and C and beta-carotene (a vitamin A
precursor), can prevent cell damage and other changes caused by oxidation. Antioxidants
act by scavenging the oxygen free radicals (molecules with an unpaired electron, which
rapidly reacts with other molecules) that cause oxidation. 1
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Apoptosis or apoplex·y
- ap·o·plex·y (àp¹e-plèk´sê) noun 1. Sudden
impairment of neurological function, especially that resulting from a cerebral hemorrhage;
a stroke. 2. A sudden effusion of blood into an organ or tissue.
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- [Middle English apoplexie, from Old French, from Late Latin apoplêxia,
from Greek, from apoplêssein, to cripple by a stroke : apo-, intensive
prefix. See APO- + plêssein, plêk-, to strike.]2
- Arteriosclerosis
- arteriosclerosis (är-tîr´ê-o-skle-ro¹sîs), general term for
a condition characterized by thickening, hardening, and loss of elasticity of the walls of
the arteries. In its most common form, atherosclerosis, fatty deposits, e.g., CHOLESTEROL,
build up on the inner artery walls; in some cases calcium deposits also form. The blood
vessels narrow, and blood flow decreases; THROMBOSIS, HEART DISEASE, and STROKE may
result. Surgical treatment is sometimes effective, but there is no specific cure. A
low-cholesterol diet and control of predisposing factors, such as HYPERTENSION, smoking,
DIABETES, and obesity, are usually recommended.1
- ar·te·ri·o·scle·ro·sis (är-tîr´ê-o-skle-ro¹sîs) noun
- A chronic disease in which thickening, hardening, and loss of elasticity
of the arterial walls result in impaired blood circulation.
- — ar·te´ri·o·scle·rot¹ic (-ròt¹îk) adjective 2
- Arthritis
- arthritis (är-thrì¹tîs), inflammation of one or more joints of
the body, usually producing pain, redness, and stiffness. It disables more people than any
other chronic disorder. A common form is osteoarthritis, a degenerative disease of the
joints that commonly occurs with aging. Rheumatoid arthritis, an AUTOIMMUNE DISEASE of
unknown cause, is a progressive, crippling joint disorder most common in women between 25
and 50. Symptomatic treatment for arthritis includes use of heat, physical therapy, and
ASPIRIN or anti-inflammatory drugs such as IBUPROFEN; remission of symptoms can sometimes
be achieved with gold salts, penicillamine, and short-term CORTISONE. Orthopedic surgery,
including artificial joint implantation, may be done in severe cases.1
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- Axon
- ax·on (àk¹sòn´) noun The usually long process of a nerve fiber that
generally conducts impulses away from the body of the nerve cell.
- [Greek axon, axis.]
- — ax¹on·al (àk¹se-nel, àk-sòn¹el) adjective2
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