Biological clocks

Biological Clocks

A biological clock is an innate mechanism that controls the physiological activities of an organism which change predictably throughout the day. These clocks are influenced by environmental cues, such as sunlight and temperature, to adjust an organism's internal environment to its external environment. Biological clocks exist in nearly all life forms, including animals, plants, fungi, and cyanobacteria.

Overview

Biological clocks are endogenous, self-sustained oscillations that organize the timing of biological systems to optimize physiological and behavioral performance. They are responsible for coordinating the timing of sleep and feeding patterns, hormone production, cell regeneration, and other biological activities.

Types of Biological Clocks

There are three types of biological clocks: circadian rhythms, ultradian rhythms, and infradian rhythms.

Circadian rhythms are the most well-known type of biological clock. These rhythms have a cycle length of about 24 hours. The term "circadian" comes from the Latin circa, meaning "around", and diem, meaning "day".

Ultradian rhythms have a cycle length shorter than 24 hours. Examples of ultradian rhythms include the 90-minute REM sleep cycle and the 3-hour cycle of growth hormone production.

Infradian rhythms have a cycle length longer than 24 hours, such as the human menstrual cycle.

Biological Clocks in Humans

In humans, the biological clock is located in the suprachiasmatic nucleus (SCN), a group of cells in the hypothalamus. The SCN controls the production of melatonin, a hormone that makes you sleepy. When it gets dark, the SCN signals the brain to produce more melatonin.

Disruption of Biological Clocks

Disruption of the biological clock, such as through shift work, jet lag, or insomnia, can have negative effects on health. Studies have linked irregular sleep patterns with various health problems, including diabetes, obesity, and depression.

See Also

• Chronobiology
• Circadian rhythm sleep disorder
• Jet lag
• Shift work sleep disorder