"Currently, more than 300 million people in China have sleep disorders " news has attracted widespread attention. In our impression, almost all creatures with long brains have to sleep. It seems to be a necessity for all mammals and most other animals.
▲Flamingos have at least one brain hemisphere awake
But among these creatures that need to sleep, some animals have mastered a "super power"-the ability of the brain hemisphere to sleep .
Generally, birds and aquatic mammals, as well as certain lizards, have this ability—that is, one hemisphere sleeps while the other hemisphere stays awake.
When only half of the brain is sleeping, only the opposite eye will be closed; that is, when the right hemisphere of the brain is asleep, the left eye will be closed, and vice versa.
▲Asleep polar bear
There are two basic types of mammalian sleep: rapid eye movement sleep (REM) and non-rapid eye movement sleep (NREM) (with three different stages) ). Generally, carnivores have the highest daily sleep requirements, omnivores have the lowest sleep requirements, and herbivores have the lowest sleep requirements. Humans sleep less than many other omnivores, but sleep abnormally little or less than other mammals.
In a normal night, people will cycle through all stages of "non-rapid eye movement sleep" and "rapid eye movement sleep" many times.
The first stage of non-rapid eye movement sleep is the transition from waking to sleep. In just a few minutes, the heartbeat, breathing, and eye movements will slow down, and the muscles will occasionally twitch and relax. brain wave relaxes from the active state when awake.
The second stage of non-rapid eye movement sleep is light sleep before entering deeper sleep. Heartbeat and breathing are slower,The muscles relax further. Body temperature began to drop and eye movements stopped. Brain wave activity slows down, but is characterized by short bursts of electrical activity.
The third stage of non-rapid eye movement sleep is deep sleep that makes people feel refreshed when they wake up. During sleep, heartbeat and breathing will drop to a minimum. The muscles are extremely relaxed, in the most difficult state to be awakened, and the brain waves become slower.
REM sleep first occurs about 90 minutes after falling asleep. Your eyes move quickly to the left and right behind the closed eyelids. The brainwave activity of mixed frequencies becomes closer to that of waking. Breathing becomes faster and uneven, and heart rate and blood pressure rise to levels close to waking up.
Most of people’s dreams occur in REM sleep. Because the arm and leg muscles are temporarily paralyzed, it is guaranteed that the body will not follow dream activities. With age, people's sleep time in REM sleep will decrease.
Therefore, in the stage of rapid eye movement sleep, it can improve learning ability and consolidate memory, and release stress and emotions.
During sleep, the brain organizes and re-orders memory and cognition, while the human brain is highly active during REM sleep. It is precisely because of the re-arrangement and combination of various fragments that people have strange dreams.
During a good sleep, the brain can perform deep learning permutation and combination to classify all items and timelines, so that people's memory is clearer.
At the same time, REM sleep paralyzes the muscles so that the body will not follow the dream. Dreams that we want may carry our backlog of various emotions and messy thoughts, and they will be completely released in the dream. During REM sleep, dopamine, which causes excitement, is also eliminated, which reduces the influence of recalling people’s emotions.
During sleep, it also promotes protein synthesis, cell renewal, growth hormone release and immune function repair and so on. At the same time, sleep is also conducive to the brain's elimination of metabolic waste, allowing the brain to operate more efficiently.
US University of Rochester, a study by showed thatThe brain metabolites that accumulate in the gaps between brain tissues are eliminated during sleep. This may be another important role of sleep.
▲ cerebrospinal fluid circulatory system
Studies have shown that in an anesthetized brain, these tissue gaps can occupy nearly 20% of the total volume. Because the lymphatic system in the brain is not well developed, the interstitial spaces act as the "scavengers" of the brain. The metabolites of the brain are washed away by the cerebrospinal fluid flowing through the interstitial space: the cerebrospinal fluid filtered by the blood is pumped from the choroid plexus of the ventricle into the brain, and penetrates into the interstitial spaces of the brain, and is finally pumped back to the cerebrospinal periphery of the brain. Membrane intravascular.
Researchers estimate that the interstitial space in the waking mouse brain accounts for 14% of the total brain volume, which increases by more than 60% under natural sleep or anesthesia, and already accounts for 23% of the brain volume. Although it does not seem to increase much on the surface, such an increase is enough to have an important impact on the flow of cerebrospinal fluid and the substances it carries.
The author found that when mice are awake, the circulation of cerebrospinal fluid is limited to the surface of the brain, but under natural sleep or anesthesia, it can penetrate deep into the brain tissue-the cerebrospinal fluid flows into the tissue when awake The amount of gap is only 5% of sleep.
As the cerebrospinal fluid flowing through the interstitial spaces during sleep increases significantly, this increases the efficiency of the brain to remove metabolites. β- amyloid is one of the metabolites. Studies have shown that this protein accumulates when a person is awake, and its accumulation is related to the onset of Alzheimer's disease. By injecting radioactive beta amyloid or other inert tracers into the cerebral cortex, it was found that they were cleared from the brains of mice twice as fast in sleep as they did when they were awake.
▲Neurotransmitter
In addition, during sleep, the release of the inhibitory neurotransmitter GABA is usually increased. If there is insufficient sleep,GABA will accumulate in the neuron and will be released in large quantities in the waking state. Increased GABA release during wakefulness usually causes damage to concentration, so lack of sleep often makes people lose their attention. It should be noted that especially to avoid driving in this situation.
Casual summary
It is conceivable that lack of sleep will reduce learning ability and memory, make excessive negative emotions backlog, damage the speed of cell repair, and may even increase Alzheimer’s disease (commonly known as dementia) Disease) risk.
So, if you see this, hurry up and sleep!
#睡日科普# #睡# #There are more than 300 million people in China with sleep disorders#
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