Introduction:
- Our sleep patterns, the ebb and flow of our daily rest, are not random but meticulously choreographed by a biological maestro known as the circadian rhythm.
- In this post, we’ll unveil the fascinating world of our internal body clock and how it influences when we sleep and wake.
- Get ready to discover the science behind those mysterious sleep patterns and how you can harness this knowledge for better sleep.
Section 1: The Body’s Biological Clock
- The term circadian comes from the Latin phrase “circa diem,” which means “around a day.” Circadian rhythms exist in all types of organisms. Circadian rhythm is the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to light changes in our environment. Our physiology and behaviour are shaped by the Earth’s rotation around its axis.
- Circadian rhythms are physical, mental, and behavioural changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark and affect most living things, including animals, plants, and microbes. Chronobiology is the study of circadian rhythms.
Section 2: The Suprachiasmatic Nucleus (SCN)
- The mastermind behind our circadian rhythm, is the Suprachiasmatic Nucleus (SCN), a small but powerful cluster of neurons in the hypothalamus responsible for circadian rhythm. The suprachiasmatic nucleus (SCN) is a bilateral structure located in the anterior part of the hypothalamus. It is the central pacemaker of the circadian timing system and regulates most circadian rhythms in the body.
- The SCN receives two types of input: photic and non-photic. The photic input comes from intrinsically photosensitive retinal ganglion cells (ipRGCs), which project through the retina-thalamic tract via glutamatergic synapses to neurons in the SCN. This helps to synchronize the circadian clock. It also sends signals and responses modulated by the SCN are numerous and include rhythms in sleep/wake cycles, locomotor, gnawing and general activity, temperature, ingestive behaviour, and rhythms of hormonal and peptide secretions.
Section 3: The Role of Light and Dark
- In the mechanism called entrainment, light serves as a signal for the SCN, to match the period and the phase to the environmental oscillator, the light/dark regime. Adjusting the period is necessary, as the endogenous rhythm, persisting in constant darkness, is close to but not exactly 24 hours. Melatonin secretion is stimulated by darkness and inhibited by light, and in coordination with the SCN, it is centrally involved in maintaining circadian rhythmicity and regulating sleep. The SCN regulates the timing of melatonin release, while melatonin feeds back to the SCN to decrease SCN neuronal firing.
- The brain then sends signals throughout the body. View Source to control organs and other systems in accordance with that time of day. When exposed to only natural light, a person’s circadian rhythm becomes closely synchronized with sunrise and sunset, staying awake during the day and sleeping when it’s dark. Visible light synchronizes the human biological clock in the suprachiasmatic nuclei of the hypothalamus to the solar 24-hour cycle. Short wavelengths, perceived as blue colour, are the strongest synchronizing agent for the circadian system that keeps most biological and psychological rhythms internally synchronized. Light can either advance (go to bed earlier) or delay (go to bed later) the circadian system depending on the timing of exposure. Under conditions of solar light exposure, light around dusk causes a delay in the clock, whereas light exposure around dawn will advance the clock.
Section 4: Synchronizing Sleep with the Stars
- Different systems of the body follow circadian rhythms that are synchronized with a biological clock in the brain. This internal clock is directly influenced by environmental cues, especially light, which is why circadian rhythms are tied to the cycle of day and night.
- They control many behavioural and physiological processes in our bodies and are strongly influenced by environmental factors such as light, noise, nutrition, sleep, temperature, and social cues. These environmental factors are fed into a complicated system of molecular feedback loops, which impact the circadian rhythm. Research suggests the ideal time to go to sleep is 10 pm, but you should focus more on having a consistent schedule and routine when it comes to hitting the hay.
Section 5: Disruptions and Modern Challenges
- Artificial light, late-night screen time, and irregular schedules can disrupt our circadian rhythm. Light exposure provides the primary time cue for the central clock in the suprachiasmatic nuclei (SCN) of the hypothalamus and suppresses melatonin synthesis by the pineal gland. Artificial light exposure at night can therefore disrupt the SCN clock and melatonin rhythm. Melatonin reduction results in daytime sleepiness and sleep disturbances.
- The cumulative long-term effects of sleep loss and sleep disorders have been associated with a wide range of deleterious health consequences including an increased risk of hypertension, diabetes, obesity, depression, heart attack, and stroke. A disruption to your body’s cycle of sleep and daytime wakefulness causes sleep disorders. Specific things may cause this to happen and it varies based on the type of sleep disorder you have. They may include A symptom of a medical condition like heart disease, asthma, pain or a nerve condition. Sleep loss can affect your mood, and your mood can affect how much and how well you sleep. Studies show people who are sleep-deprived report increases in negative moods (anger, frustration, irritability, sadness) and decreases in positive moods.
Section 6: Resetting the Clock
- Wake up every day at the same time: Keeping a regular sleep schedule will help reset your circadian rhythm. By going to sleep and waking up at the same time every day, your body will learn to adjust to the new rhythm. Avoid eating and physical activity later in the day. This is especially important in the two hours before going to bed.
- Reduce exposure to artificial light at night.
- Get outside in the morning.
- Ask your doctor about melatonin supplements.
- Research suggests that maintaining a consistent sleep schedule can help you get better quality rest (and more of it). The practice is also associated with healthier body composition (especially in elderly individuals) and a lower risk of heart disease. Keep a Regular Sleep Schedule
- Changing up your sleep routine on the weekends could negatively affect circadian rhythms over time as well as other factors affecting your well-being and longevity. And, it may make it that much harder to wake up early again on Monday morning!
Section 7: The Circadian Rhythm’s Influence Beyond Sleep
- Circadian rhythms affect multiple aspects of cognitive functions (mainly via arousal), particularly those needed for effort-intensive cognitive tasks, which require considerable top-down executive control. These include inhibitory control, working memory, task switching, and psychomotor vigilance. Circadian rhythms dictate multiple processes in the body, including alertness or sleepiness, appetite, and body temperature. The body’s internal clock is naturally aligned with the cycle of day and night. Circadian rhythms can be disrupted by travel, work, or an underlying issue.
- Scientists also study organisms with irregular circadian rhythms to identify which genetic components of biological clocks may be broken. Understanding what makes biological clocks tick may lead to treatments for jet lag, sleep disorders, obesity, mental health disorders, and other health problems. Research into circadian rhythms has revealed that there are certain peak times during the day or night when drugs are most effective. This has led to the development of guidelines with the timing of drug dosing for a range of medications e.g. antiepileptic drugs (Baraldo).
Conclusion:
- The 4 circadian rhythms are
- Diurnal (night and day) Circadian (24 hours) Ultradian (less than 24 hours) Infradian/Circalunar (1 month)
- To sum up the key takeaways: our sleep patterns are not arbitrary but are influenced by our circadian rhythm. The SCN controls the production of melatonin, a hormone that makes you sleepy. It receives information about incoming light from the optic nerves, which relays information from the eyes to the brain. When there is less light — for example, at night — the SCN tells the brain to make more melatonin so you get drowsy.
- Readers are advised to respect their body’s internal clock, maintain healthy sleep patterns, and make lifestyle choices that support circadian harmony for a more restful and energized life.
- You are reminded that by syncing with the stars, you can uncover the secret to better sleep and overall well-being.
Dr Jagatjit Singh Virk
@jagatjitvirk
