How the Physiology of Sleep Impacts Our Health and Well-Being

Table of Contents

Last Updated on February 25, 2023 by Mike Robinson

What is the Physiology of Sleep?

The physiology of sleep is separated into two categories. The two types of sleep are very different from each other: rapid eye movement (REM) sleep, which is when you dream, and non–rapid eye movement (NREM) sleep. The changes between NREM and REM sleep seem to be controlled by how neurons in the brainstem restrict each other.

Specific neurons become more active when REM sleep is triggered, while others become almost silent. Because these neurons switch between being active and not being active, NREM and REM sleep cycles happen during the sleep period.

Theories About Sleep

Bremmer’s passive theory of sleep, developed in 1935, was one of the earliest attempts to explain lucid dreaming. This theory stated that by bedtime, the excitatory regions of the brainstem would have become dormant after a day of use. Our sleeping would be comparable to charging a mobile phone battery.

But after several years we learned more about the physiology of sleep. Additional experiments were performed, the theory became obsolete, and we began to see a different vision. The theory that accompanies this process currently says that sleep occurs through active inhibition.

However, the brain does not sleep while you do it, and your work style changes to match the process. We still don’t know why humans sleep. As you read above, the dream is a priority need, and not sleeping can harm your health.

Because of physiology of sleep, the average person can’t go for more than two nights without sleep. It appears that disorders would gradually increase in severity and have serious consequences starting the third night without sleep. This would manifest as hallucinations and convulsions and affect areas like focus, memory, and mood.

The 4 Stages of Sleep

Non-REM (NREM) sleep has 3 stages, while REM sleep has only one.

NREM Phase

This stage is also known as “no-Rem,” meaning “non-rapid movement of the eye.” This stage is the first point of contact with the dream. It is the first dream state we enter, and it will occupy 75% of our dreams for most adults. The NREM stage has four phases that form the dream’s characteristics. These are as follows:

Stage 1- NREM-Phase 1

At this point, we are either very sleepy or completely unconscious. As the alpha rhythm diminishes, so does the awake state. There is still some tension in the muscles. There are no longer any detectable beta waves.

Stage 2- NREM-Phase II-III

The dream is light at this point, the Alpha rhythm is gradually fading, and muscle tone is still present even though we are asleep. We gradually become aware of the theta waves.

Stage- NREM-Phase IV

Phase four is the stage of deep sleep. The encephalographic rhythm is very low, and muscle tone is maintained or may be significantly lower. Delta waves appear in our brains.

This stage differs in that the muscular tone is gradually increased, and the brain waves change progressively depending on the relaxation of the body.

REM phase

The REM phase is the paradoxical dream phase. During this phase, the brain has an activity that resembles when we are awake. During this phase, rapid eye movements take place. What we dream of occurs during this phase.

No clear theory exists about why ocular movement occurs during the REM phase.

The Physiology of Sleep Cycles

Adults usually have about 8 hours of sleep per day. If the 8 hours are continuous, it will take about 4 or 5 cycles. Each cycle is a complete sleep phase (from stage I to REM phase) lasting between 90 and 120 minutes each.

The typical distribution is as follows:

Phase I: Approximately 1.5% of the total cycle would occur during this phase. This means that if the cycle lasts 100 minutes, only 1.5 minutes of the body would be in phase I.
Phase II: This phase represents approximately 25% of the total cycle. In a cycle of 100 minutes, 25 minutes would be the duration of Phase II.
Phases III and IV: These two phases would last 45% of the total cycle. In a 100-minute cycle, these phases would last approximately 45 minutes.
The REM phase during the cycle would have a duration of 25% of the total cycle. So in a cycle of 100 minutes, only 25 minutes correspond to REM sleep.

How Much Do People Sleep?

The amount of sleep throughout the day differs according to age, daily activity, and health. Babies spend most of their time sleeping, though as they get older, their waking periods get longer and longer. It’s interesting to learn that babies have a higher proportion of REM sleep than adults and that that proportion will decline during childhood until it reaches a normal level.

Sleeping requirements for adults are lower than for infants. In adults, the need to sleep is less than in infants. An adult can sleep between 5 and 9 hours and perform well throughout the day. Although it is best to sleep between 7 and 8 hours a day to have good health and high quality of life,

The quantity of sleep is affected by various life events and circumstances. For instance, we will require more sleep during periods of intense intellectual activity than during periods of high stress.

Older people have less need for sleep, and their rest periods are shorter. They usually wake up during the night, and the percentage of phase IV sleep is low. However, the REM phase seems invariable throughout life regarding its duration in the sleep cycle.

Our Biological Clocks

A huge part of the human physiology of sleep is the circadian rhythm, which is a biological clock that controls the sleep cycle. Day and night, each has its own individual 24-hour cycles. Every 25 hours or so, your body goes through a cycle of sleep and wakefulness known as the circadian rhythm. This information is intriguing because it suggests that human beings are susceptible to the pull of recurring patterns.

One of our biological clocks is located in the brain. This wristwatch regulates the duration of both non-REM and REM sleep. A biological system must respond to external stimuli to maintain a regular circadian rhythm. Of these external stimuli, light and the time to wake up are the most important and influential.

The time we go to bed is also important, and while we can establish a routine that forces us to get into bed at a specific time, we typically cannot control the precise moment we fall asleep.

What if a person is isolated from these stimuli, meaning he doesn’t notice changes in light, temperature, or activities? That person would also follow a normal biological sleep rhythm. The human body will follow the needed rhythm without outside help.

What Are Dreams?

When we talk about the physiology of sleep or the act of sleeping, we refer to a natural and physiological state in which a person is less alert and aware because they are resting. And while the subject’s outward calmness may indicate an inner state of tranquility, this impression is entirely false; a sleeper’s body does not stop and functions as intricately as when we are awake.

Each stage or phase of sleep is accompanied by changes to the body, just as the dream consists of varying degrees of intensity or depth.

Because the brain is constantly active and moving, it does not rest when we dream as the rest of our bodies. While we sleep, we also have what is commonly called “dreams,” which are strange experiences.

As you just read, dreams happen during the REM phase. Because of this, many experts think that dreams cause the movement of the eyes. Dreams are colorful and move around like a movie. You sometimes dream during the deep sleep phase. The only difference is that these dreams are more vague.

The part of our brain called the reticular system, connected to the cerebral cortex and the frontal lobes, becomes active during rapid eye movement (REM) sleep. When awake, these regions are also stimulated. Because of the activation of these structures, we experience the sensation of actually living the dream we are having. What we feel in our dreams is real.

In addition, the amygdala and cingulate cortex, two key limbic system components, are highly active in sleep. Since this system is in charge of our emotions, it stands to reason that we would experience these emotions while dreaming.

During sleep, the prefrontal cortex, which is responsible for mental reasoning, is inhibited, so this can give us relevant information about the little logic that our dreams often have.

Your nightly sleep is a natural process, and I hope this article has taught you something you didn’t already know. I’ll wrap up this article by leaving you with six bits of information about dreams you probably didn’t know.

6 Surprising Facts About Dreams

Blind people also dream. People who are blind from birth can dream just like those who can see. The difference is that a blind person’s dreams involve other senses, like sound and smell.
Women dream of sex the same amount as men do. Like men, women dream about having sex. The circumstances, quantity, and frequency are equal. Perhaps the only difference is what is said.
Not everyone dreams in color; only about 12% of people have black-and-white dreams. This information is intriguing because it is believed that before the invention of television, people used to dream in black and white and that it was only after this invention that we began to dream in color.
The animals also dream. If you have an animal companion, you have undoubtedly noticed that occasionally, while sleeping, it moves as if performing an action. Animals have dreams just like people do. They have the same brain waves when they dream as we do.
Your body reacts to your dreams as if they were real experiences. When we dream, our experience at that precise moment is recorded as a real experience.
We only dream of the faces we already know. When you dream, your brain does not create new faces. The faces of the people that appear in our dreams are those of people we have previously met. Even though we might not recognize the face or know the person, it is unquestionably a part of our memory.