At HRC, we are constantly exploring the holistic power of plants and the mind, body, and skin. In this issue, we will introduce basic information on sleep.
We sleep to rest our bodies and minds. Even if we try to go a few days without sleep, after a few days we reach our limit. This is because sleep is essential for us humans and animals to survive. Sleep deprivation causes abnormalities in homeostasis and the immune system, resulting in poor physical condition, memory impairment, and difficulty concentrating.
Conversely, sleep can be expected to improve memory, concentration, and intellectual ability. The phenomena of increased memorization and dramatic improvement in sports and musical instruments can also be attributed to sleep.
When you fall asleep, you first enter a phase called “non-REM sleep” and then “REM sleep,” and these two types of sleep are repeated during sleep. This is called the “sleep cycle.
Non-REM sleep is important for brain and body rest; sympathetic function decreases and parasympathetic function increases. In contrast, during REM sleep, the brain is active, and both sympathetic and parasympathetic nervous systems fluctuate greatly. During REM sleep, the brain is active and both sympathetic and parasympathetic nerves fluctuate greatly.
Many physiologically active substances are involved in the regulation of sleep and waking, and the following is a list of typical brain substances.
・Melatonin, serotonin
Melatonin is the hormone best known for leading to sleep. Its secretion is inhibited by light entering the eyes, so it is less secreted during the day and more at night, leading to drowsiness. It is synthesized from a hormone called serotonin, but serotonin works in the opposite direction, promoting waking.
・orexin
Most of us are active continuously during the day and go to sleep at night. One of the important substances for maintaining this daytime wakefulness is a nerve substance called orexin. When orexin is not working, we become sleepy even in important or tense situations when we should be.
Many other substances, including acetylcholine and cortisol, are also involved in sleep. Many other substances, including acetylcholine and cortisol, are also involved in sleep. Figure 1.
The mechanism that generates the daily rhythm of waking up in the morning and going to sleep at night is called circadian rhythm, which is regulated by the above-mentioned hormones such as serotonin, melatonin, and orexin. On the other hand, some hormones are secreted in accordance with this circadian rhythm. Growth hormone (GH) is secreted in large amounts during sleep, especially during non-REM sleep1). This substance is considered important in the skin at various stages of skin formation, and a link between low GH levels and skin aging has been suggested2).
In other words, a good, deep sleep is expected to help maintain healthy skin.