Food, water, air, and shelter--- the basic necessities of human life Yet, humans wouldn’t last very long without sleep, as well. Just like how a set amount of calories and cups of water are needed each day, a certain amount of sleep is required to maintain a healthy and happy schedule. .
For those no longer willing to stare at their ceiling for hours every night or those who let their alarms ring for hours past their set time, this is the sign to confront these burdening issues. Understanding how sleep works may drive a person one step closer to achieving their ideal slumber
Parts of the brain associated with sleep:
Sleep is a result of many brain functions and processes. Several locations of the brain have a role to play and their synchronization is what allows for these tiny chemical reactions to result in the bigger picture of sleep.
Hypothalamus:
This vital structure situated near the base of the brain contains groups of nerve cells that correspond to sleep. A large cluster of thousands of cells called the suprachiasmatic nucleus (SCN) is sent signals from the eyes entailing light exposure.
This ties into the circadian rhythm cycle which functions as the main mechanism for sleep to start and end, as well as sets the stage for the other parts of the brain to perform their tasks. The circadian rhythm acts as a biological clock--- following the amount of light exposure--- and sends signals to the brain to sleep and night and wake in the morning
Brain stem:
Located at the base of the brain, the brain stem communicates with the hypothalamus to control the body’s transition between sleep and wake. This process is catalyzed by proto-sleep cells produced in both the hypothalamus and brainstem which reduce the activity of nerve cells by inhibiting nerve transmissions. These cells also serve to relax muscles during REM sleep.
Thalamus and Cerebral Cortex:
The cerebral cortex stores and processes information from our surroundings and is most active during the day. Behaving as an intermediate between our environmental stimuli and our brain, the thalamus connects the flow of information from our senses to our cerebral cortex.
For most of our sleep, we are not connected to the outside world and the thalamus remains inactive. However, during REM sleep, the thalamus becomes active and is often what fuels our dreams.
Pineal Gland:
After receiving signals from the SCN, the pineal gland directs the production of melatonin which invokes sleep after a decrease in light exposure. Those who cannot process light exposure due to compromised eyesight or damaged hypothalamus can take melatonin as a drug to induce sleepiness.
Basal forebrain:
This part of the brain releases the chemical, adenosine, from both the basal forebrain and most likely other regions of the brain which increases sleep drive. The consumption of caffeine blocks the adenosine neurotransmitters causing prolonged periods of activeness instead of sleepiness.
Amygdala:
This structure is heavily involved in processing emotions and becomes increasingly active during REM sleep as emotions tend to be present in dreams.
Now that all the players in this prevalent process of sleep have been revealed, it's time to understand the rules of the game itself.
Two types of sleep:
Non-REM sleep is the pathway in which we are able to fall asleep. During the stages of NREM sleep, we are able to go from fully functioning and active to lying unconscious in a deep slumber. Circadian rhythms are the main mechanisms for NREM.
The Three Main Stages of NREM Sleep:
NREM Stage 1:
In this brief period lasting only a few minutes, a person transitions from eyes wide open to eyes covered with both their eyelids and blanket.
As one is settling into sleep, their heartbeat and breathing slow and muscles begin to relax and there is light eye movement behind the eyelids.
Sleep in this stage is known to be the lightest as one could easily be woken up and transition back into their daily functions. In fact, one who exits this stage may not have even been aware of their temporary state of dormancy.
NREM Stage 2:
This stage is known to cover the largest portion of the sleep cycle, although it is not the deepest sleep, as one could still be easily awoken with a tap or call.
One’s heartbeat and breathing slows down further and all eye movement has ceased. Furthermore, one’s body temperature decreases and heat is released, paving the way for a more comfortable sleep
NREM Stage 3:
At this point, the body enters the final stage in NREM sleep ---the deepest and heaviest sleep in the cycle. Heartbeat and breathing have completely slowed and muscles are fully relaxed.
Many bodily functions that contribute to one’s health occur during this stage. Large bouts of cell division take place for growth, tissue repair, and cellular regeneration to ensure the body is fresh and functional during the day. Additionally, our body produces T-cells or white blood cells to strengthen the immune system
Finally we enter REM sleep or, in its full form, Rapid Eye Movement sleep. There are two parts to REM sleep with a few key differences. Phasic REM sleep yields the namesake of this section of the sleep cycle as its main characteristic is periodic bursts of rapid eye movements and muscle twitching. Tonic REM, however, does not have any eye movement, and the heart rate is decreased.
Breathing and heart rate increases and approaches our vital sign statistics during the day. Although our muscles are significantly more relaxed or paralyzed, twitching may occur throughout REM sleep. Areas of the brain become increasingly active as this is the portion of sleep in which dreams occur, which are primarily drawn from emotion and the senses.
The cycle between Non-REM, and REM sleep continues throughout the night, restarting about every 90 minutes. On an average day, the cycle may repeat four or five times in total.
Sleep is regulated by homeostasis which ensures the body receives its necessary amount of sleep and adjusts the deepness or intensity depending on how much is needed.
How the body reacts to sleep
It is common knowledge that sleep has many health benefits and is necessary for growth. However, many of the changes our bodies undergo while we sleep seem to fly over most of our heads.
Other than the fluctuations in breathing, heart rate, temperature, and eye movement, there are many other changes that occur as well.
We enter a fasting state
In physiological terms, fasting refers to the metabolic status of someone who has not eaten for a while, such as a few hours, after digestion. Excess carbohydrates from meals are stored as glycogen in the liver and are released when our blood sugar level drops during our “fast”. Therefore we do not feel hungry when we sleep as glycogen is being released to keep our blood sugar level stable
Hormones are released
Hormones from the thyroid which influence metabolism and growth are dispatched in higher quantities during sleep. The “Stress” hormone cortisol is decreased during sleep and rises back up when one is closer to waking. The opposite is true for melatonin, a hormone highly involved in the sleep cycle
Our brain is given time to organize
During sleep, the glymphatic system (or waste-removing cycle) detoxifies our neurons and clears out waste or debris. As a result, our heads are clearer when we wake up.
Memory is also affected as short-term memories are sorted into long-term and irrelevant information is deleted as well. The unclogging of our neurons also results in increased effectiveness in the amygdala, striatum, hippocampus, insula, and medial prefrontal cortex. These correspond to learning, decision-making, problem-solving, creativity, concentration, and emotion.
Reasons for sleep disorders
Sleep disorders are caused by a multitude of reasons and can have a wide range of effects. However, the main link between all of them is that they impact one’s daily life just as much as their sleep.
Sleep disturbances may be tied to physical or chemical components. People whose SCN or retinas are damaged may have an erratic sleep schedule because their brains cannot process light exposure and their sleep-wake cycle is affected.
However, more commonly, environmental and psychological factors play into the lack of sleep.. These include pulling all-nighters for work or school which ignores one’s bodily cues for sleep for the sake of staying up late, the consumption of drugs thatintercept certain neurotransmitters meant to induce sleep, or confusing one’s biological clock by sleeping more while the world is light and staying active when it is dark.
Sleep disorders--- sullied by the stigma surrounding the word “disorder are actually quite common. ”. Hypersomnia and insomnia both deprive one of their necessary vitality to function during the day and improve/maintain good health.
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