What is sleep?
Everyone knows what sleep, but most people would find it difficult to define. Sleep is the intermediate state wakefulness and death, wakefulness being regarded as the active state of all the animal and intellectual functions, and death as that of their total suspension. During sleep, our senses are disengaged and we are temporarily unresponsive to our environment. Sleep involves processes affecting both our behavior and also our physiology (the way the body works).

Why do we need sleep?
Sleep is important to health, and insufficient sleep can lead to problems with various body systems, including the immune system, the heart and circulatory system, and hormone secretion. Also, poor quality or insufficient sleep can lead to impairment of daytime functioning, exercise daytime sleepiness, and problems with memory.

How much do we know about sleep?
The study of sleep is an evolving science. We know a lot about many disorders of sleep but not enough about others. Answers to even the commonest questions about sleep are not always simple or straightforward, and sometimes there is no answer at all. Studies in sleep and sleep disorders are relatively new area of research compared with many other areas of human health.

What is the sleep wake cycle?
The sleep-wake cycle is the alternation between the states of being awake and being asleep. One theory of sleep states that the amount of sleep we experience depends on the length of time we awake prior to sleep. So, the longer you are awake and the more tired and sleepy you become, the greater the urge for you to fall asleep and the longer you are likely to sleep in order for your body to attain normal function again. Some researchers believe there is a separate sleep wake cycle that runs on its own rhythm but also interacts with the circadian rhythm. Many other theories have been developed in order to define how and why we sleep and what the basic drives to sleep are.

What role does corticol play in the sleep wake cycle?
Corticol is the stress response hormone of the body. It has marked circadian rhythm, and levels in the blood will vary during the day and night. Corticol levels are at their lowest during slow wake sleep at night. The highest corticol levels are in the early morning before sunrise and awakening. This means that your body is prepared to be fully active when you get up.

What role does body temperature play in regulating sleep?
Sleep onset is likeliest to occur in the downward phase of the temperature cycle. In other words, we are most likely to sleep when our body temperature is falling. A secondary peak in sleepiness occurs in the afternoon and corresponds to afternoon napping. Sleep stops as the body temperature curve rises.

Is environment temperature important in sleep?
It is usually more conducive to sleep in a slightly cooler rather than warmer environment, as this matches the dip in core body temperature that occurs during sleep. Extremes of temperature (hot and cold) disrupt sleep.

Which parts of the brain are involved in sleep?
The important part of the brain involved in the co-ordination of the sleep process is called the reticular activating system (RAS). It comprises a large number of nerve cells throughout the brain and is responsible for regulating wakefulness. When RAS neurons switch off, alertness id reduces. There is a significant and continuous interplay between the RAS and other sleep regulating areas in the brain. These include the thalamus, spinal cold, pineal gland, raphe nuclei, basal forebrain, hippocampus, and the suprachiasmatic nucleus.

What role do light and darkness play in regulating sleep?
Light activates special receptor cells at the back of the eye (retina), which in turn affect the suprachiasmatic nucleus. This has link to other parts of the brain that regulate sleep and wakefulness, including the pineal gland, which produces melatonin. Exposure to light increase wakefulness while darkness has the opposite effect. Light is thus important to the regulation of sleep and wakefulness and helps our circadian rhythm on track. Light is an effective cue for wakefulness in all humans, except those who lack light receptors in the eyes (certain forms of profound blindness).

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This entry was posted on Saturday, September 1st, 2007 at 3:02 am and is filed under Insomnia. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.