The Homeostatic Process
The homeostatic process reflects a pressure for sleep that results from the overall balance of sleep and waking. Accordingly, as people remain awake longer, greater pressure for sleep accumulates from this process. In fact, this homeostatic process might be considered as beginning from the moment of awakening and continuing until sleep occurs again. Normally, the homeostatic process should enhance the ability to fall asleep at one’s habitual bedtime. However, purely from the homeostatic influence, the timing of sleep would not matter, as long as one was getting a sufficient amount of sleep. That is, one could sleep at random times and with various durations at any hour throughout the 24-hour day. Of course, that is not how most people exist, which is one reason it is evident that other factors also regulate the sleep-wake cycle. As noted above, the habitual sleep amount varies among species. For humans, the homeostatic drive for sleep seems to be about eight hours (one-third of the daily sleep-wake cycle). Sleep in some manner discharges the homeostatic pressure, thereby allowing subsequent alertness. Obviously, this balance occurs over a relatively short time period—just a few days. People cannot remain awake effectively for extended periods, nor can they sleep indefinitely. One cannot sleep continuously for one week and then remain awake the following two in order to satisfy the 1:2 ratio of sleep to waking.
Homeostatic sleep pressure generally represents the sleep need discussed above. This balanced drive for sleep can be seen as minimal during the daytime when people have been getting fully adequate nighttime sleep. It should be at a moderate level that enhances sleep onset as bedtime approaches. If a person is deprived of sleep, the homeostatic sleep pressure can cause a marked degree of sleepiness. Excessive sleepiness can result from acute sleep loss, chronic sleep insufficiency, or a combination of these. Such mixtures of sleep insufficiency are rather common in our society.
Source: David N. Neubauer, “Understanding Sleeplessness: Perspectives on Insomnia,” The Johns Hopkins University Press, Baltimore 2003
Republished by Health Care Programs