Its most important function is to foster the daily alternation of sleep and wakefulness. The biological clock is housed in a pair of tiny bilateral brain areas called the suprachiasmatic nuclei . The major role of the biological clock in the regulation of sleep and wakefulness is to provide an internal and very powerful wake-up signal to the rest of the brain. We call this signal clock-dependent alerting . CDA fosters consolidated periods of peak alertness, high energy, and optimal mental performance at specific times during the day.
Sleep is regulated homeostatically.
Most people think that a heavy meal, a warm room, a comfortable bed, a boring lecture, an alcoholic beverage will cause sleepiness. None of these things cause sleepiness. Rather, they unmask sleepiness. If you do not have a sizable sleep debt, you will never get sleepy in the daytime. The onset of drowsiness is the moment when staying awake requires a conscious effort, usually an effort to keep the eyes open.