“Sleep is time for the general body and brain to shut down and rest.” Is it True or False? The answer is False. Sleep is an active process. No organ or regulatory system ‘shuts down.’ There is only a slight decrease in metabolic rate. On the other hand some brain activity increases during sleep and specific hormones, such as growth hormone and melatonin secretion increase during sleep. We spend about 1/3 of our lives sleeping.
During sleep, the growth and restoration of the nervous, skeletal and muscular systems take place. Adequate sleep is essential for the normal functioning of the endocrine and immune systems and is absolutely important for maintaining mood, memory, and cognition (intellectual activity such as thinking, reasoning, remembering). Hence, the importance of sleep for our health cannot be ignored.
In fact, disturbances in sleep are associated with a wide range of serious health problems including obesity, diabetes, hypertension, depression, and sleeping tablets are among the most widely prescribed medicines in the world. Lack of sleep has been implicated in major industrial disasters and car and workplace accidents.
What makes us sleep at night and wake up each morning:
Certain brain areas, hormones and brain chemicals (neurotransmitters) help to maintain the sleep-wakefulness cycle in our body.
Brain areas responsible for sleep-wakefulness:
A few small areas of the brain are responsible for keeping us awake or asleep of which – the suprachiasmatic nucleus or SCN is very important. The SCN is also responsible for maintaining the Circadian Rhythm or the ‘Biological Clock’. Some brain areas promote wakefulness while others promote sleep. The areas that promote wakefulness inhibit those that promote sleep and vice versa.
What happens when the Circadian Rhythm is disrupted:
When we attempt to stay awake against the schedule dictated by our biological clock, our mental and physical performance is greatly diminished. The result is excessive sleepiness or poor sleep, loss of concentration, reduced alertness, slowed reflexes, nausea, irritability and poor performance in work. Conditions that can cause disruption of circadian rhythms include shift work, jet lag, and sleep disorders.
Neurotransmitters and Hormones Responsible for maintaining the Sleep-Wakefulness pattern:
The neurotransmitter adenosine and hormone melatonin play significant roles in maintaining the sleep-wakefulness pattern. Adenosine induces sleep by inhibiting wake-promoting neurons and interestingly, caffeine inhibits the action of adenosine and therefore maintains wakefulness. On the other hand, melatonin prepares the body for sleep and while one sleeps, melatonin prepares the body for sleep and while one sleeps, melatonin goes to work.
Sometimes it is referred to as the body’s ‘trash collector’ because it goes to every cell in the body and cleans out the free radicals and other toxins that are harmful to our body. Melatonin is perhaps the most powerful anti-oxidant of our body.
Electro-en-cephalogram or EEG of sleep
EEG is the brain activity recorded in the laboratory with the help of electrodes placed on the scalp. Sleep has been divided into stages according to EEG records of activities in the brain during sleep and eye movements.
The Stages of Sleep
There are 5 stages of sleep during a normal night. Stages 1-4 or non-rapid eye movement sleep (non-REM/NREM) and rapid eye movement sleep (REM). During non-REM sleep, all the restorative functions of sleep occur. During REM sleep, memories and thoughts from the day are processed and we dream. Stages progress cyclically from 1-4, then REM, then restarts back at stage 1. One complete cycle takes about 90-110 minutes. Non-REM sleep is also called ‘Quiet Sleep’ and REM sleep is called ‘Dreaming Sleep’.
Stage 1: Drowsiness
This is the stage of drowsiness when one passes on from wakefulness to light sleep. Body temperature begins to drop, muscles relax, and eyes often move slowly from side to side. People in this stage of sleep lose awareness of their surroundings, but they are easily jarred awake.
Stage 2: Light Sleep
This is the first stage of true sleep lasts about 10 to 25 minutes. One spends about half the night in the stage 2 sleep. During this stage, the eyes are still and heart rate and breathing are slower than when awake.
Stage 3: Deep Sleep
The brain becomes less responsive to external stimulation, making it difficult to wake the sleeper. Breathing becomes more regular. Blood pressure falls, and pulse rate slows. Blood flow is directed less toward the brain, which cools measurably. Most restorative functions of the body take place in stage 3 of sleep. There is no eye or muscle movement and this is the stage when sleepwalking, bedwetting occurs.
Stage 4: REM Sleep
During this stage, the brain becomes extremely active thinking and dreaming. There is an increase in heart rate, blood pressure, breathing rate and body temperature. Eyes jerk rapidly but limb muscles are temporarily paralyzed. Men may experience an erection during REM sleep. Most dreams occur during this stage and if awoken, most people remember their dreams. Studies have found that REM sleep facilitates learning and memory.
What are dreams made of?
We have all wondered sometime or the other whether our dreams serve any purpose or what does it mean. There are several views regarding this:
The Freudian view:
Sigmund Freud, in the year 1900 proposed that dreams are meaningful representations of the unconscious mind in which we reveal our hidden conflicts, desires, and fears, in a somewhat disguised form, while the Sceptics argue that dreams are merely aimless and chaotic images formed by the neurotransmitters in the brain. On the other hand, the Combined views as expressed by some researchers have intertwined the psychological and neurochemical approaches. One scientist, for example, observed that patients who sustained injuries and lesions in the front part of the brain, no longer dreamed. This suggests that dreaming involves areas in front of the brain that are connected to urges, impulses, and appetites. Other research suggests that dreaming plays a role in helping consolidate the day’s memories, attaching associations and emotions and helping to retain important events.
However, complicated all these views seem we do like to pursue our dreams, don’t we?
Even though all of us would like to enjoy a good night’s sleep there are many of us who, unfortunately, cannot live up to their dreams because they rarely get a chance to dream. Sleep disorders include a range of problems from insomnia to narcolepsy and is gradually affecting more and more people on this planet, every day.
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