Saturday, May 26, 2012

Why Do We Sleep

Why do we sleep? Scientists have developed many theories why we need sleep. Our bodies seem to regulate sleep the same why it regulates our eating habits and breathing. Sleep is good for the body and plays an important part in our health. We feel better after a good night’s sleep because sleep makes us more alert and energized to get through the day. Sleep like eating and breathing is another life sustaining activity and without enough sleep we function poorly. Looking at sleep patterns in other animals to see if there are similarities or differences that might tell us something about sleep’s role researchers have suggested the possible theories.

One of the initial theories called the adaptive or evolutionary theory proposes that lack of activity at night served as a survival function by keep the body safe in times when it was for the most part exposed to dangerous elements; like being killed by a predator. This behavioral approach could have evolved to become what we now identify as sleep. Some argue saying it would have been safer to stay awake in times of trouble to react (fight or flight). They see no advantage to being asleep if safety is vital. You could counter with the fact that instead of running or fighting off your enemy you could hide and stay very still and sleep just might be the result.

Another theory suggests that the primary function of sleep was to conserve energy when food supplies were least abundant. Although this is less apparent today when there are plenty of food sources, at one time we needed to reserve our energy when we had to hunt for our next meal. Energy metabolism is reduced during sleep because a person’s body temperature and need for food decreases during sleep. Some scientists believe sleep is a primary function to help us conserve energy and considers this concept part of the inactive theory. While other scientists argue that the purpose of sleep may not be restorative. In fact, they argue that the very question “why do we sleep?” is mistaken, and that the real question should be “why are we awake?” If you are safe and warm and fed, it is a waste of energy to be awake and moving around (and possibly getting into trouble). Far better, this argument goes, is to be awake only when you have to and sleep when it suits you.

[caption id="attachment_1803" align="alignright" width="260" caption="Brain Plasticity"][/caption]

We have known for a while that sleep restores what is lost in our mind and body while we are awake. Sleep repairs and rejuvenates our muscle growth, tissues, protein synthesis and releases our growth hormone. Without sleep we lose all immune function and in a matter of weeks, we die. Sleep also is important to cognitive function. When we are conscious neurons in our brain produce adenosine, a by-product of the cells’ activities. This build-up is thought to be one factor that leads to the awareness of feeling tired. As long as we are awake, adenosine accumulates and while we sleep it is dispelled from our brain, therefore when we wake up we feel more alert.

Recently the most compelling theory why we need sleep is based on the changes in structure and organization of the brain. This theory known as brain plasticity or neuroplasticity refers to the susceptibility to physiological changes of the nervous system, due to changes in behavior, environment, neural processes, or parts of the body other than the nervous system. Sleep plays a critical role in brain development for infants and young children. Infants spend as much as 13 -14 hours per day asleep. Half of that time is spent in REM sleep, the sleep cycle where dreams occur. Sleep and brain plasticity is associated with adults as well and is seen when sleep deprivations causes low performance levels.

Although these theories are unproven scientist continue to make efforts in finding out what happens while we sleep and what controls our sleep/wake cycles that help us live a long healthy life.

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