Dictionary

atrioventricular Pertaining to the upper chambers of the heart (atria) and the lower chambers of the heart (ventricles).

atrioventricular node The electrical relay station between the upper and lower chambers of the heart. Abbreviated AV node. Electrical signals from the atria must pass through the AV node to reach the ventricles. The AV node, which controls the heart rate, is one of the major elements in the cardiac conduction system. The AV node…

atrium An entry chamber. On both sides of the heart, the atrium is the chamber that leads to the ventricle.

atrophic vaginitis Thinning of the lining (endothelium) of the vagina due to decreased production of estrogen. Atrophic vaginitis may occur with menopause.

atrophy A wasting away or diminution. Muscle atrophy is a decrease in muscle mass, often due to extended immobility.

atropine A drug, made from the belladonna plant, that is administered via injection, eye drops, or in oral form to relax muscles by inhibiting nerve responses.

AST Aspartate aminotransferase.

asthenia Weakness. Lack of strength.

asthenic 1 Having a slender, light body. Ectomorphic. 2 Weak. Lacking in strength.

asthma A common lung disorder in which inflammation causes the bronchi to swell and narrow the airways, creating breathing difficulties that may range from mild to life-threatening. Symptoms include shortness of breath, cough, wheezing, and chest tightness. The diagnosis of asthma is based on evidence of wheezing and is confirmed with breathing tests. Many allergens…

asthma, exercise-induced Asthma triggered by vigorous physical activity. It primarily affects children and young adults because of their high levels of physical activity, but it can occur at any age. Exercise-induced asthma is initiated by the fall in airway temperature during rapid breathing followed by rapid reheating with lowered ventilation. The more heat that is…

asthma, thermally induced See asthma, exercise-induced.