Physiology, Circadian Rhythm

Excerpt

The regulation of sleep is processed by the homeostatic physiology of the circadian rhythm, the sleep/wake cycle. Circadian rhythm is the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to light changes in our environment. Our physiology and behavior are shaped by the Earth’s rotation around its axis. This biological circadian system has evolved to help humans adapt to changes in our environment and anticipate changes in radiation, temperature, and food availability. Without this endogenous circadian clock, Homo sapiens would not be able to optimize energy expenditure and the internal physiology of the body.