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While We Sleep, Our Mind Goes on an Amazing Journey

Stage Two Sleep

We spend about half our sleeping time in stage 2. It can last up to 50 minutes during the first 90-minute sleep cycle, and less during subsequent cycles. 

During this time the brain consolidates the information that has been collected during the waking hours. It makes connections you might not make otherwise. It also curates which memories to keep and which to delete.

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While We Sleep, Our Mind Goes on an Amazing Journey

While We Sleep, Our Mind Goes on an Amazing Journey

https://www.nationalgeographic.com/magazine/2018/08/science-of-sleep/

nationalgeographic.com

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Key Ideas

Our sleep-wake pattern

Our molecular clock inside our cells aims to keep us in sync with the sun

When we disregard this circadian rhythm, we are at a greater risk for illnesses such as diabetes, heart disease, and dementia.

The lifestyle imbalance

Thomas Edison said that sleep is "a bad habit." Like Edison, we seem to think of sleep as an adversary and try to fight it at every turn. The average American sleeps less than the recommended seven hours per night, mostly due to electric lights, television, computers, and smartphones. 

However, we are ignoring the intricate journey we're designed to take when we sleep.

Stage One Sleep

When we fall asleep, the nearly 86 billion neurons in our brain starts to fire evenly and rhythmically. Our sensory receptors become muffled at the same time.

The first stage of shallow sleep lasts for about 5 minutes.

Stage Two Sleep

We spend about half our sleeping time in stage 2. It can last up to 50 minutes during the first 90-minute sleep cycle, and less during subsequent cycles. 

During this time the brain consolidates the information that has been collected during the waking hours. It makes connections you might not make otherwise. It also curates which memories to keep and which to delete.

Stage Three Sleep

Some scientists consider stage 3 and 4 to be one stage.  Your body rests during these stages to help cells recover. Your cells produce the most growth hormone here to mend your bones and muscles.

While all this is happening, your muscles are fully relaxed. Mental activity is limited, including dreaming. 

Stage Four Sleep

We can remain in stage 4 - similar to a coma or brain death - for only about 30 minutes before the brain wakes up and falls back to sleep again. 

Even healthy sleepers wake several times a night, but might not be aware of it.

REM

Rapid Eye Movement or REM follows after the four stages of NREM (non-REM) sleep and occupies about one-fifth of total rest time in adults.

During REM, all vivid dreaming takes place. Our internal temperature is at its lowest. Our heart rate increases and our breathing is irregular. Generally, our muscles are immobilized, and we are incapable of physical response, except for our eyes and ears. However, our brain is fully active.

Sleep more essential than food

Sleep is essential for maintaining a healthy immune system, body temperature and blood pressure. The lack of sleep prevents us from regulating our moods well or recovering promptly from injuries.
Sleep reduces the risk of developing dementia. Our neurons deflate by 60 percent while we sleep, widening the spaces between them to receive metabolic waste. During sleep, spinal fluid wash this waste away.

Sleep deprivation facts

  • More than 80 million American adults suffer from chronic sleep deprivation.
  • Fatigue contributes to more than a million auto accidents each year.
  • About one-third of us will suffer from some form of sleep disorder.
  • People with Kleine-Levin syndrome will sleep nearly nonstop for a week or two and return to regular cycles without any side effects.
  • 4 % of US adults take sleeping pills in any given month.

Effects of too little sleep

  • The prefrontal cortex, the place in the brain that controls decision-making and problem-solving, is the first to suffer from not enough sleep.  It causes you to be more irritable, moody and irrational.
  • Sleeping less than six hours a night increases the risk of depression, psychosis, and stroke.
  • Lack of sleep is tied to obesity. The stomach and other organs overproduce ghrelin, the hunger hormone, which causes overeating.

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One of the areas of the brain that’s most active during dreaming is the amygdala - the part of the brain associated with the survival instinct and the fight-or-flight response.

One theory suggests dreams may be the brain’s way of getting you ready to deal with a threat. Fortunately, the brainstem sends out nerve signals during REM sleep that relax your muscles. That way you don’t try to run or punch in your sleep.

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One theory for why we dream is that it helps facilitate our creative tendencies. 

Without the logic filter, you might normally use in your waking life that can restrict your creative flow, your thoughts and ideas have no restrictions when you’re sleeping.

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About 80% of our sleeping is of the SWS variety, identified by slow brain waves, relaxed muscles and deep breathing.

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Dreaming accounts for 20% of our sleeping time.

The length of dreams can vary from a few seconds to almost an hour. During REM sleep, the brain is highly active. The muscles are paralyzed, and the heart rate increases. Breathing can become erratic. 

Sleep quantity

Although eight hours is the common mention, optimum sleep can vary from person to person and from age to age.

One review that worked through 320 research articles concluded 7 - 9 hours of sleep are enough for adults. According to experts, too little or too much sleep can both have a negative impact on your health.

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Snoring isn’t harmful

Although snoring may be harmless for most people, it can be a symptom of a life-threatening sleep disorder called sleep apnea, especially if it is accompanied by severe daytime sleepiness. 

You can "cheat" on sleep

Sleep experts say most adults need between seven and nine hours of sleep each night for optimum performance, health, and safety. 

The resulting sleep deprivation has been linked to health problems such as obesity and high blood pressure, negative mood and behavior, decreased productivity, and safety issues in the home, on the job, and on the road.

Turning up the radio

... opening the window, or turning on the air conditioner are effective ways to stay awake when driving.

These "aids" are ineffective and can be dangerous to the person who is driving while feeling drowsy or sleepy. 

It's best to pull off the road in a safe rest area and take a nap for 15-45 minutes. Caffeinated beverages can help overcome drowsiness for a short period of time. 

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