Human Circadian Rhythm Biological Sleep Clock Poster

A circadian rhythm is an endogenously driven roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed, in plants, animals, fungi and cyanobacteria (see bacterial circadian rhythms). The term "circadian" comes from the Latin circa, meaning "around", and diem or dies, meaning "day". The formal study of biological temporal rhythms such as daily, tidal, weekly, seasonal, and annual rhythms is called chronobiology. Although circadian rhythms are endogenous ("built-in", self-sustained), they are adjusted (entrained) to the environment by external cues called zeitgebers, the primary one of which is daylight. Image reproduction rights can be found in the link near the bottom of this description. Sign up to Mr. Rebates for FREE and save 12% on any zazzle order in addition to a $5.00 sign up bonus All Rights Reserved; without: prejudice, recourse or notice (U.C.C. 1-308) Image Reproduction Rights: http://commons.wikimedia.org/wiki/File:Biological_clock_human.svg sleep "biological clock" "circadian rhythm" "human biological clock" diagram chart circadian chronobiology zeitgebers "circadian biological clock" "human circadian biological clock" "sleep pattern" sleeping "human sleep" "sleep chart" "sleep diagram" biology "human biology" "biology chart" "biology diagram"