Circadian rhythm

Main thing

Circadian rhythm is our body's natural clock that tells us when to sleep and when to be awake. It works on a 24-hour cycle. This rhythm affects our sleep, mood, and even our body temperature. It responds to light, which helps set the clock every day. The nervous and endocrine systems are key players in this process.

1. Morning Light Exposure: Light hits our eyes and signals the brain's suprachiasmatic nucleus (SCN), part of the nervous system.

2. Cortisol and Body Temperature Rise: The adrenal glands release cortisol, and our body temperature increases, making us alert. As the day progresses, cortisol levels begin to decline.

3. Afternoon Energy Dip: Energy levels dip temporarily in the afternoon.

4. Evening Melatonin Release and Temperature Drop: The pineal gland releases melatonin, and our body temperature decreases, preparing us for sleep. As we approach bedtime, melatonin levels increase, inducing sleepiness, while cortisol levels drop, allowing us to wind down.

Example: On a cloudy day with little sunlight, our body might not receive enough light to properly regulate our circadian rhythm. This can lead to feeling sleepy or lethargic throughout the day, as the lack of light affects the release of cortisol and melatonin.

Terms

• Nervous System - A network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body. Example: The nervous system uses light to help set our circadian rhythm.

• Endocrine System - The collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things. Example: The endocrine system releases hormones like cortisol and melatonin that affect our circadian rhythm.

• Melatonin - A hormone released by the pineal gland that makes us feel sleepy. Example: Our body releases more melatonin in the dark, helping us to sleep.

• Cortisol - A hormone released by the adrenal glands that helps us wake up and feel alert. Example: Our body releases cortisol in the morning, which helps us start the day.

An analogy

Think of the circadian rhythm like an internal clock that runs in the background of a computer. Just as the computer clock schedules tasks for specific times, our circadian rhythm schedules our body's activities, like when to wake up or go to sleep.

Example: Just as a computer might start a backup at 2 AM, our body starts to release sleep hormones when it's time to sleep.

A main misconception

Many people think that if they get enough sleep at any time of the day, it's just as good as sleeping at night. However, our circadian rhythm aligns with daylight and darkness, so sleeping at the right time is crucial for our health.

Example: Sleeping during the day and being awake at night can disrupt our natural rhythm and lead to health issues.

The history

1. 4th century BC - Theophrastus mentions a plant that sleeps at night, an early observation of circadian rhythms.

2. 18th century - Jean-Jacques d'Ortous de Mairan studies plants and their daily cycles, furthering understanding of circadian rhythms.

3. 20th century - Scientists identify the suprachiasmatic nucleus in the brain as the location of the circadian clock.

4. 21st century - Research expands into how circadian rhythms affect health, leading to new treatments for sleep disorders.

"Life is a series of natural and spontaneous changes. Don't resist them; that only creates sorrow. Let reality be reality. Let things flow naturally forward in whatever way they like." - Lao Tzu, an ancient Chinese philosopher and writer, known for his wisdom on natural harmony and change.

Three cases how to use it right now

1. Improving Sleep: To improve sleep quality, see the sun as early as possible, avoid screens before bedtime, and keep bright lights to a minimum in the evening.

2. Managing Jet Lag: Adjusting light exposure based on the time zone we're traveling to can help reset our circadian rhythm and reduce jet lag.

3. Shift Work: Workers can use light therapy to adjust their circadian rhythm to better match their work schedules, improving alertness and reducing health risks.

Interesting facts

• Plants, animals, and even bacteria have circadian rhythms.

• The term "circadian" comes from Latin words meaning "about a day."

• Disrupting the circadian rhythm can increase the risk of chronic diseases.

• The Nobel Prize in Physiology or Medicine 2017 was awarded for discoveries related to the molecular mechanisms controlling the circadian rhythm.

• Circadian rhythms can influence the effectiveness of medications.