Mechanisms of Sleep and Wakefulness: Three Systems—Melatonin | Orexin | Homeostatic Regulation

Don't you wish you could sleep soundly?

Here, we discuss tips for a good night's sleep.

What is the mechanism behind sleep and wakefulness?

1. The Mechanism of Melatonin

~Melatonin regulates sleep rhythm~

We have a small "pineal gland" in our brains,
from which a hormone called "melatonin" is secreted.

When its blood concentration is measured, it rapidly increases around 8-10 PM, regulating our body's internal clock.
In other words, it plays a role in keeping the body in an active state during the day and a resting state at night.

"Melatonin"... Adjusts the human body's rhythm to a 24-hour cycle

Humans live on Earth in a 24-hour cycle, don't they?

If a person were to live for several weeks in a dark cave without a clock, their rhythm would not be 24 hours but 25 hours. This phenomenon is called free run.
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In fact, melatonin adjusts and aligns it to 24 hours.

Case Study

Sleep-wake cycle shifts from 24 hours to 25 hours

A patient I previously treated had a 25-hour sleep-wake rhythm.
Please refer to the two figures below.

Figure 1 shows a 24-hour sleep rhythm, but Figure 2 shows a 25-hour sleep rhythm, indicating that the sleep-wake rhythm shifts by one hour each day.
This is a condition called "non-24-hour sleep-wake syndrome," which is a bit technical.

2. The Mechanism of Orexin

~Orexin awakens the brain sharply~

In the lower part of the cerebrum, there is an important region called the hypothalamus.

It serves as the center for appetite, body temperature, sleep, and the autonomic nervous system.

From here, a hormone called "orexin" is secreted, which is deeply involved in the functions of sleep and wakefulness.

To use a movie analogy, it's like a situation where instructions from the organization are delivered to 007 via a tape recorder.

The instructions disappear quickly, but 007, having received them, becomes sharp and alert, working with a multi-faceted mind.

​If no instructions come, he might fall asleep due to lack of stimulation.

There are three major factors that stimulate orexin.

① The stimulus of hunger due to nutritional status

② The stimulus of morning indicated by the body clock

③ The stimulus of heightened emotion due to psychological state

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When these stimuli are received, orexin secretion increases, maintaining a state of wakefulness.

As shown in the figure below, it maintains a good balance like a balancing doll.

Conversely, when orexin secretion decreases, it leads to wakefulness → sleep.

Related to this, there is something everyone experiences daily.

If you eat too much delicious food, sleepiness often sets in afterwards. This can be attributed to orexin.

When blood glucose levels rise due to carbohydrates in food, the glucose concentration in cerebrospinal fluid also increases.

This temporarily weakens the activity of neurons that activate orexin, causing sleepiness.

3. Another Sleep-Wake System

~Actually, three systems regulate~

So far, regarding sleep and wakefulness, we have discussed:

​① Melatonin, related to the body clock

② Orexin, an arousal regulator

.

Additionally,

③ The homeostatic regulatory system

is also involved.

While it may sound a bit complex, "GABAergic neurons" that control the sleep center are at work.

Please see the diagram showing the relationship between the three.

In this way, when sleep and wakefulness switch, these hormones maintain a balance and guide us.
It can be said that they lead us to a good night's sleep, as if inducing good dreams.

Brahms's "Sandmännchen" (The Little Sandman) has been known as a lullaby.
Since ancient times, it has been believed that when a sleep fairy sprinkles sand into children's eyes, they are led to a good night's sleep.
May you be embraced by healing music and have good dreams.

4. To Get Good Sleep

~Both hormones cooperate for a good rhythm~

The fact that you can be active during the day and sleep soundly at night in your daily life is thanks to these mechanisms.

However, in modern society, too many stresses weigh down on us, and many people suffer from sleep disorders.

Ideally, we would maintain proper eating, exercise, and sleep as part of a regular lifestyle, but in reality, it's not that simple.
If necessary, related medications are also available and can be utilized.

However, for working healthily in both mind and body, it is best to utilize music as medicine, or "sound medicine."

Tap the jacket photo to easily preview on YouTube

This is a healing album designed to promote metabolism and beautiful sleep.
The natural reverberations from live piano recordings in a concert hall create a blissful and soothing space.

Utilize "sound medicine" for a healthy daily life.

Hiroshi Bando

Doctor of Medicine
Councilor, Japan Society of Anti-Aging Medicine
Branch Manager (Shikoku), Japanese Society of Integrative Medicine
Part-time Lecturer, Tokushima University

Graduated from Tokushima University, obtained ECFMG certification, and completed clinical training in family medicine in the USA. Specializes in anti-aging, carbohydrate restriction, music therapy, sports medicine, etc. Participated in the National Sports Festival as an ice skater (1999-2003). Chairman of the 9th Annual Meeting of the Japanese Society for Music Therapy (2009). Silver Medal at the 3rd European International Piano Competition (EIPIC) in Japan (2012). Chairman of the Annual Meeting of the Japan Primary Care Association (2017).
Editor-in-Chief of 4 international English medical journals (2024). Authored over 30 books, over 2,000 publications, and over 500 English papers. Representative of "New Elderly Association" Tokushima chapter.

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Official website: https://pianomed.org/