Biological Rhythms

Made by @agreyr

Biological rhythms

Repeating, predictable fluctuations over time; almost all biological functions have a rhythm

Ultradian rhythm

Any biological process that repeats more than once in a day (activity, feeding, some hormone release)

Infradian rhythm

Any biological process that repeats less than once in a day (menstrual cycle, breeding cycle in some animals, seasonal patterns of depression, hibernation)

Circadian (daily) rhythm

Any biological process that cycles through changes in approximately 24 hours (hormone levels, body temp, etc.)

Generated by an endogenous (internal) clock

Adapt to the light-to-dark cycles of the day based on Zeitgebers

Diurnal

Awake during the day, sleep at night (humans & primates)

Nocturnal

Active during dark periods (most other mammals)

Zeitgebers

Environmental cues that control the timing of circadian rhythms

Can be manipulated in laboratory settings; presumed to work via mechanisms in the suprachiasmatic nucleus of the hypothalamus (SCN)

Most obvious one is the circadian sleep-wake cycle

Free-running circadian cycle

In an environment devoid of Zeitgebers, humans and animals still maintain the circadian rhythms, approximately 25 hours in humans; they do not have to be learned

Phase shift

Shift in activity caused by a stimulus (night shift workers)

Entertainment

The process of shifting (jet lag)