Is it sleep simply turning off the brain and going into a deep coma?
Sleep is lot more complex than what you think. In fact it is state of being probably just as
important as being awake. There are some that have said that sleep is a waste of time, and
they try to sleep as little as possible. Well, the consequence is detrimental. These people
tend to be chronically tired and mentally not focused. They also tend to get sick more often
and in the long run their health suffers. “I’m so tired!” When you hear these words you can
almost bet that it’s because of improper sleep. But, what is it that we really do while we
sleep?
Sleep is a complex and vital part of our daily routine. Sleep is not simply “turning down” the
brain and resting. It is rather a complex set of behavior with neurochemical basis. With the
setting of the sun and changes in our environment that come with it, certain messages are
sent to our brain. Within our brain, just behind our eyes, lie set of nerve cells
(suprachiasmic nucleus) that act as our internal clock. These group of cells has intrinsic
rhythm that acts as our “clock” and function as mediator of our circadian rhythm. These cells
are under direct influence of light, especially the sun. After sun sets, there are series of
neurochemical changes that take place including rise in melatonin level which eventually leads
us to sleep.
There are also temperature changes in our body that follow circadian pattern. Our body
temperature is lowest during deepest part of sleep. As our body starts to “warm up” we
wake up in the morning. Body temperature continues to rise during the day with a slight dip
in the midafternoon (“afternoon dip”). When temperature falls we generally tend to feel
sleepy. This is why we feel sleepy after lunch, and it is not because of heavy meal. Our
level of alertness seems to follow our temperature curve. Our body temperature peeks after
dinner, and it now starts to cool down. This is when we get sleepy. It is interesting to know
that our internal clock, the suprachiasmic nucleus, sits just above the hypothalamus, the
master controller of our metabolism.
As we fall asleep, an interesting phenomenon occurs. We all recognize that that our muscles
relax as we fall asleep. If you see someone sleepy, their facial muscles begin to relax even
before there are fully asleep. The eyes get “heavy” as we have difficulty keeping them open.
The head starts to nod if we happen to be sitting up. If you observe carefully as one falls
asleep there is sudden relaxation of the whole body as he/she enters sleep. Our upper
airway also relaxes along with chest wall muscles. This results in change in breathing pattern
and we slightly under breath during sleep. Some of us start to snore with relaxation of the
airways, and in individuals with sleep apnea their upper airway collapses as they start having
apneic episodes.
Sleep is organized into non-REM and REM sleep. These two sleep states appear to be
distinctly different as wake is to sleep. Non-REM is divided into stages one through four.
Stage 3 and 4 is known as delta sleep or slow wave sleep. Non-REM is thought to be
more of brain resting as there is decrease in energy consumption by the brain. We generally
start our sleep with light sleep entering into slow wave sleep. Most young kids have increased
amount of slow wave sleep compared to adults. In kids it is during the first stage of slow
wave sleep that growth hormone is released by the brain. Increased level of exercise has
shown increased slow wave sleep, and it is thought that this stage of sleep has some kind
of restorative function. During the night brain cycles between non-REM and REM sleep at
approximately 90 minutes cycles. As night progresses REM phase become longer. About 25%
of our sleep is spent in REM sleep.
REM, as you know, stands for rapid eye movement. REM is also referred to as active sleep
or paradoxical sleep. Interestingly in REM our brain is highly turned on and utilizes more
energy than when we are awake. REM is thought to be a primitive type of sleep and it is
the first sleep seen in developing brain. Because brain is highly “turned on” other interesting
phenomenon occurs. Our brain literally paralyzes our body to prevent it from moving. There
are series of changes that occur in the brain stem resulting in near complete paralysis that
occur at the level of the spinal cord. In fact, our spinal reflexes such as knee jerk reflex is
absent during REM. If you ever awoken and was paralyzed for few seconds and could not
move even though you’re awake, this is where brain delayed turning off part of REM
mechanism. Most people have experienced this feeling and occasional episodes are thought to
be normal. REM is also associated with dream state and when people are awakened during
REM they usually will have a vivid dream recall.
The question was what happens when we sleep. Well, we are not sure. But we know what
happens when sleep is partially deprived. Most obvious change we notice is that the person
is tired and lacks energy. There is also an obvious lack of concentration. Even if you are not
tired studies have shown that with minimal decrease in sleep time, day time performance
suffers. There is also strong evidence that your metabolism will be disturbed. Various
hormones that are released by the brain to control wake and sleep also appear to control
hunger and satiety and vice versa. Chronic sleep deprivation has been shown to slow your
metabolism leading to weight gain as well as fatigue. Your immune function also appears to
be directly tied to sleep pattern. Lack of proper sleep will compromise overall immune system
leading to illness. Severe sleep deprivation studies done in animals often result in animal
dying with overwhelming infections. In fact most optimal way to improve your immune function
is to optimize sleep.
There are strong psychological effects from lack of sleep. Other than being tired, sleepy
person tends to be cranky and short tempered. Chronic sleep loss is associated with fatigue
and depressed mood. Divorce rate among couples with sleep problem is much higher than the
average. Most treatable cause of attention deficit disorder is in fact sleep deprivation, most
common being sleep apnea.
We know sleep has various important functions, but we still try to get by on less sleep and
more caffeine. There is really no substitute especially for growing kids and young adults.
Setting a regular sleep pattern is basis of good sleep hygiene.