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How do natural circadian rhythms help the body prepare for sleep 

Circadian rhythms direct a wide variety of functions from daily fluctuations in wakefulness to body temperature, metabolism, and the release of hormones. They control your timing of sleep and cause you to be sleepy at night and your tendency to wake in the morning without an alarm. Your body’s biological clock, which is based on a roughly 24-hour day, controls most circadian rhythms. Circadian rhythms synchronise with environmental cues (light, temperature) about the actual time of day, but they continue even in the absence of cues. These rhythms are internally generated patterns that follow a roughly 24-hour cycle and are influenced by external cues of which light is the most potent. Photoreceptors in our eyes receive the light signals and set in train the timing of our body clocks.

Here’s how circadian rhythms aid in preparing the body for sleep:

Sleep-wake cycle: One of the primary functions of circadian rhythms is to regulate the sleep-wake cycle. The circadian clock signals the brain and body when it’s time to sleep and wake up. As evening approaches and darkness sets in, the body’s internal clock triggers the release of the hormone melatonin, which promotes drowsiness and signals that it’s time for sleep.

Body temperature regulation: Circadian rhythms also influence body temperature regulation. Typically, body temperature decreases slightly in the evening, signaling to the body that it’s time to wind down and prepare for sleep. The drop in temperature helps facilitate the onset of sleep and maintains a stable sleep state throughout the night.

Hormone production: Circadian rhythms affect the production and release of various hormones involved in sleep regulation. For example, cortisol, known as the “stress hormone,” follows a diurnal pattern, with higher levels in the morning and lower levels at night. This helps promote alertness during the day and gradually decreases to facilitate sleep onset.

Neurotransmitter balance: Circadian rhythms also impact the balance of neurotransmitters in the brain, which are chemical messengers that regulate brain function. The levels of neurotransmitters such as serotonin, dopamine, and norepinephrine fluctuate throughout the day and play a role in promoting wakefulness or sleep. As evening approaches, the balance shifts towards increasing the release of sleep-promoting neurotransmitters, preparing the body for sleep.

Sleep-related behaviours: Circadian rhythms influence a range of sleep-related behaviors, such as timing and duration of sleep. These rhythms help synchronise our sleep patterns with the external environment, ensuring that we sleep during the night when it’s dark and wake up in the morning when it’s light. The timing and consistency of sleep contribute to maintaining a healthy circadian rhythm.

Even losing just 1 hour of sleep over a few days can have an effect. It can lead to a decrease in performance, mood, and thinking. Getting regular, adequate amounts of sleep is important. It can help you feel awake and refreshed during the day. It can also help you feel relaxed and sleepy at night. This helps make you ready for a long, restful night of sleep.

By aligning our sleep patterns with the natural circadian rhythm, we can optimise our sleep quality and wake up feeling refreshed. Disruptions to the circadian rhythm, such as irregular sleep schedules or exposure to artificial light at night, can negatively affect the body’s ability to prepare for sleep and result in sleep difficulties.