Vocabulary Pages 788-790 & 865-878

feedback – a primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation.

positive feedback – a physiological control mechanism in which a change in some variable triggers mechanisms that amplify the change.

thermoregulation – maintenance of body temperature within a range that enables cells to function efficiently.

conduction – direct transfer of thermal motion (heat) between molecules of the environment and those of the body surface.

convection – transfer of heat by the movement of air or liquid past the surface of a body.

radiation – emission of electromagnetic waves produced by all objects warmer than absolute zero.

evaporation – loss of heat from the surface of a liquid that is losing some molecules as gas.

ectotherm – creature that warms the body by absorbing heat from its surroundings.

endotherm – creature that derives most or all body heat from its own metabolism.

vasodialation – an increase in the diameter of superficial blood vessels (cools body).

vasoconstriction – a decrease in the diameter of superficial blood vessels (warms body).

countercurrent heat exchanger – a system of veins and arteries which are close together that transfer heat from one to another.

nonshivering thermogenesis – hormonal triggering of heat production.

brown fat – fat behind the neck in some mammals for rapid heat production.

acclimatization – adjustment to a new range of environmental temperatures over a period of days or weeks.

stress-induced proteins – proteins that synthesize heat-shock proteins when “shocked” by a rapid change in temperature.

heat-shock proteins – molecules that help maintain integrity of other cells threatened by extremities in environment.

hibernation – long term time in which the body’s temperature is lowered as an adaptation to winter cold and food scarcity.

estivation – slow metabolism and inactivity that enables animals to survive long periods of time with little food in great heat.

transport epithelium – layer(s) of epithelial cells that regulate solute movements.

ammonia – soluble waste molecules that easily pass through cell membranes.

urea – mildly toxic and slightly soluble waste molecules.

uric acid – very toxic and insoluble, complex waste molecules.

osmolarity – osmotic pressure (total solute concentration expressed as molarity).

osmoconformer – animal with equal osmolarity as its environment.

osmoregulator – animal that must adjust its inner osmolarity to match that of the environment.

stenohaline – animals that cannot tolerate substantial changes in external osmolarity.

euryhaline – animals that survive large fluctuations in external osmolarity.

anhydrobiosis – adaptation in which the organism survives in a dormant state when its habitat dries up.