1.8 Processes Related to Homeostasis

Acclimatization

Environmentally induced improvement in functioning of a physiological system with no change in genetic endowment

Adaptation

A biological characteristic that favors survival in a particular environment; (neural) decrease in action potential frequency in a neuron despite constant stimulus

Circadian Rhythm

Occuring in an approximately 24 hour cycle

Entrainment

Adjustment of biological rhythm to environmental cues

Free-Running Rhythm

Cyclical activity driven by biological clock in absence of environmental cues

Melatonin

An amine derived from tryptophan produced in the pineal gland and that plays a role in circadian rhythms

Negative Balance

Loss of substance from body exceeds gain, and total amount in body decreases; also used for physical parameters such as body temperature and energy

Pacemaker

Neurons that set rhythm of biological clocks independent of external cues; any neuron or muscle cell that has an inherent autorhythmicity and determines activity pattern of other cell

Pineal Gland

Part of the epithalamus of the brain; produces melatonin involved in circadian rhythms

Pool

The readily available quantity of a substance in the body; often equals amounts in extracellular fluid

Positive Balance

Gain of substance exceeds loss, and amount of that substance in body increases

Stable Balance

Net loss of substance from body equals net gain, and amount of substance in body neither increases nor decreases

Total-Body Balance

The balance of any substance in the body; depends upon the net gain or net loss of the substance in the body and may be negative, positive, or stable