Circadian rhythm

A daily cycle of activity observed in many living organisms. The "'circadian rhythm"' refers to the 24-hour cycle of biological processes that regulate numerous physiological activities in living creatures, including humans. These internal clocks, which are controlled by external elements such as light and temperature, regulate several aspects of an organism's behavior, physiology, and metabolism, including sleep-wake cycles, body temperature, hormone synthesis, and digestion.

Origin and Function

The term "circadian" is derived from the Latin words "circa" (around) and "diem" (day) and reflects the 24-hour cycle of these circadian rhythms. Circadian rhythms are endogenously created, or internally driven, but can also be altered by external stimuli, such as light, which assist synchronize the rhythm with the environment. This is referred to as "'entrainment"'.

The primary purpose of circadian rhythms is to optimize the physiological activities of an organism according to the time of day. For instance, in humans, the circadian rhythm helps prepare the body for nighttime sleep and daytime activity. It controls tiredness and alertness by regulating the release of hormones such as melatonin and cortisol.

The Role of the Suprachiasmatic Nucleus

In animals, the suprachiasmatic nucleus (SCN) of the hypothalamus functions as the primary pacemaker of circadian rhythms. Around 20,000 neurons get direct input from the retina, enabling the SCN to detect changes in light and synchronize the circadian cycle accordingly.

The SCN transmits messages to various regions of the brain and body, including the pineal gland, which regulates the production of melatonin, the hormone that controls sleep. When the SCN detects darkness, it sends a signal to the pineal gland to produce more melatonin, which induces sleepiness. In contrast, melatonin production reduces when light is detected, increasing wakefulness.

Circadian Rhythm Disorders

Many sleep and health issues can result from disruptions to the circadian cycle. The following are frequent circadian rhythm disorders:

• Delayed sleep phase disorder (DSPD): A disorder defined by difficulties falling asleep and waking up at customary times, resulting in a later-than-desired shift in sleep pattern.
• The opposite of DSPD, "'Advanced sleep phase disorder"' (ASPD) is characterized by a sleep pattern that is changed earlier than expected, with patients falling asleep and waking up earlier than normal hours.
• Jet lag is a transitory circadian rhythm problem caused by rapid travel across many time zones, with symptoms including exhaustion, sleeplessness, and gastrointestinal difficulties.
• Shift work sleep disorder: A circadian rhythm disturbance encountered by those who work nocturnal hours or rotating shifts, resulting in difficulty with sleep, alertness, and general health.

Importance of Keeping a Healthy Circadian Rhythm

Keeping a healthy circadian rhythm is essential for health and wellness as a whole. Many health conditions, including sleep disorders, obesity, diabetes, cardiovascular disease, and mood disorders, such as depression and anxiety, have been associated to circadian rhythm disturbances.

Practices that can help support a healthy circadian rhythm include:

• Keeping a regular sleep routine
• Experiencing natural light during the day
• Evening exposure to artificial light, especially blue light from screens, should be limited.
• Developing a soothing nighttime routine
• Caffeine and alcohol should be avoided close to bedtime.
• Developing an environment conducive to sleep that is cold, dark, and silent

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