Well,why do we sleep?
The fact that sleep makes us feel better and that going without sleep,makes us feel worse,puts up the question in our minds,'why sleep is necessary?'
One way to think about the function of sleep is to compare it to another of our life - sustaining activity - eating. Hunger is a protective mechanism that has evolved to ensure that we consume the nutrients our bodies require to grow,repair tissues and function properly. Both eating and sleeping are regulated by powerful internal drives. Going without food produces the uncomfortable sensation of hunger,while going without sleep makes us feel overwhelmingly sleepy. And just as eating relieves hunger and ensures that we obtain the nutrients we need, sleeping relieves sleepiness and ensures that we obtain the sleep we need. Still, the question remains: Why do we need sleep at all? Is there a single primary function of sleep, or does sleep serve many functions?
A simple - counter argument to one theory is that it is always safer to remain conscious in order to be able to react to an emergency (even if lying still at night). There doesn't seem any advantage of being unconscious or asleep if safety is Paramount. The primary function of sleep is to reduce an individual's energy demand and expenditure during part of the day or night, especially at times,when it's least efficient to search for food. Research has shown that energy metabolism is significantly reduced during sleep (by as much as 10 percent in humans and even more in other species). For example, both body temperature and caloric demand decrease during sleep, as compared to wakefulness. Such evidence supports the proposition that one of the primary functions of sleep is to help organisms conserve their energy resources.
Rejuvenating aspects of sleep are specific to the brain and cognitive function. For example, while we are awake, neurons in the brain produce adenosine, a by-product of the cells' activities. The build-up of adenosine in the brain is thought to be one factor that leads to our perception of being tired. (Incidentally, this feeling is counteracted by the use of caffeine, which blocks the actions of adenosine in the brain and keeps us alert.) Scientists think that this build-up of adenosine during wakefulness may promote the "drive to sleep." As long as we are awake, adenosine accumulates and remains high. During sleep, the body has a chance to clear adenosine from the system, and, as a result, we feel more alert when we wake.
One way to think about the function of sleep is to compare it to another of our life - sustaining activity - eating. Hunger is a protective mechanism that has evolved to ensure that we consume the nutrients our bodies require to grow,repair tissues and function properly. Both eating and sleeping are regulated by powerful internal drives. Going without food produces the uncomfortable sensation of hunger,while going without sleep makes us feel overwhelmingly sleepy. And just as eating relieves hunger and ensures that we obtain the nutrients we need, sleeping relieves sleepiness and ensures that we obtain the sleep we need. Still, the question remains: Why do we need sleep at all? Is there a single primary function of sleep, or does sleep serve many functions?
A simple - counter argument to one theory is that it is always safer to remain conscious in order to be able to react to an emergency (even if lying still at night). There doesn't seem any advantage of being unconscious or asleep if safety is Paramount. The primary function of sleep is to reduce an individual's energy demand and expenditure during part of the day or night, especially at times,when it's least efficient to search for food. Research has shown that energy metabolism is significantly reduced during sleep (by as much as 10 percent in humans and even more in other species). For example, both body temperature and caloric demand decrease during sleep, as compared to wakefulness. Such evidence supports the proposition that one of the primary functions of sleep is to help organisms conserve their energy resources.
Rejuvenating aspects of sleep are specific to the brain and cognitive function. For example, while we are awake, neurons in the brain produce adenosine, a by-product of the cells' activities. The build-up of adenosine in the brain is thought to be one factor that leads to our perception of being tired. (Incidentally, this feeling is counteracted by the use of caffeine, which blocks the actions of adenosine in the brain and keeps us alert.) Scientists think that this build-up of adenosine during wakefulness may promote the "drive to sleep." As long as we are awake, adenosine accumulates and remains high. During sleep, the body has a chance to clear adenosine from the system, and, as a result, we feel more alert when we wake.
Comments
Post a Comment