Chapter 13 Flashcards
diurnal animal
organism that is active chiefly during daylight
circadian rhythm
Day–night rhythm.
metabolic syndrome
combination of medical disorders, including obesity and insulin abnormalities, that collectively increase the risk of developing cardiovascular disease and diabetes.
biological clock
neural system that times behavior.
biorhythm
inherent timing mechanism that controls or initiates various biological processes.
what processes cycle daily?
Not only does human waking and sleep behavior cycle daily, so also do pulse rate, blood pressure, body temperature, rate of cell division, blood-cell count, alertness, urine composition, metabolic rate, sexual drive, feeding behavior, and responsiveness to medications. The activity of nearly every cell in our bodies, including gene expression, also has a daily rhythm.
What do biological clocks help with?
allows an animal to anticipate events in advance and prepare for them both physiologically and cognitively. And unless external factors get in the way, a biological clock regulates feeding times, sleeping times, and metabolic activity so that they are appropriate to day–night cycles. Biological clocks also regulate gene expression in every cell in the body so that cells function in harmony.
period
time required to complete a cycle of activity.
circannual
yearly; migratory cycles of birds
circadian
Daily; human sleep–wake cycle
ultradian
Less than a day; human eating cycles
infradian
more than a day; human menstrual cycle
do humans have an endogenous biological clock?
yes, it governs sleep-wake behavior
given no external cues, will people stay on a 24 hour cycle?
more or less, but may range from 25-27
free-running rhythm
Rhythm of the body’s own devising in the absence of all external cues.
Zeitgeber
environmental event that entrains biological rhythms: a “time giver.”
entrain
Determine or modify the period of a biorhythm.
rule of thumb to explain the period of free-running rhythms in light or dark
animals expand and contract their sleep periods as the sleep-related period expands or contracts.
when are Zeitgebers effective?
both sunrise and sunset
how many times per day can clocks be adjusted?
morning light sets the biological clock by advancing it, and evening darkness sets the clock by retarding it.
light pollution
exposure to artifical light that changes activity patterns and so distrupts circadian rhythms.
jet lag
fatigue and disorientation resulting from rapid travel through time zones and exposure to a changed light–dark cycle.
problems associated with light pollution
a great deal of inconsistent behavior associated with accidents, daytime fatigue, alterations in emotional states, and obesity and diabetes.
suprachiasmatic nucleus (sCn)
master biological clock, located in the hypothalmus just above the optic chiasm.