What is the biological clock?
The body's internal clock regulates daily rhythms. These rhythms include physical, behavioral, and mental changes that occur over a 24-hour period and primarily respond to light and darkness in the organism's environment.
The master biological clock is located in the brain and consists of thousands of neurons that help synchronize bodily functions and activities. This means regulating bodily activities at specific times, such as 24-hour body functions such as sleep and wakefulness, as well as functions that last longer than 24 hours, such as the menstrual cycle in women. What functions does the biological clock control over a 24-hour period?
In addition to controlling sleep and wakefulness, the body's internal clock controls other 24-hour functions such as:
Body temperature.
Immune system.
Hunger time.
Why do people have different sleep and wake times?
Many people notice that there is a natural variation in their sleep and wake times throughout the day. Sleep is regulated by two systems:
The first is sleep/wake homeostasis.
The second is the circadian biological clock.
The sleep/wake homeostasis system alerts the body to the need for sleep if it remains awake for a long period of time. It also helps maintain adequate sleep throughout the night to compensate for the hours of wakefulness.
How does the circadian clock control sleep and wakefulness?
The circadian clock is controlled by a part of the brain called the suprachiasmatic nucleus (SCN), a group of neurons in the hypothalamus that responds to light and dark signals.
Light travels to the SCN via the optic nerve of the eye, signaling to the internal clock that it is time to wake up. The SCN also transmits signals to other parts of the brain that control hormones, body temperature, and other functions that play a role in making us feel sleepy or alert. For example, in the morning, with exposure to light, the suprachiasmatic nucleus sends signals such as:
Raising body temperature.
Producing hormones such as cortisol.
Delaying the release of hormones such as melatonin, which is associated with the onset of sleep and is produced at nightfall. Melatonin levels rise in the evening and remain elevated throughout the night, promoting sleep.