Pathways to Sleep I: An Introduction
Such is not the case when we speak about being “tired” and needing to get some sleep. Our brain is not offering a suggestion. Rather, it is commanding that we fall asleep. It is very hard to ignore this command. We will tend to fall asleep – even if we are driving a car or trying to watch a movie. The demand for sleep can lead to the inconvenience of a missed movie or to the much more serious consequences of an automobile crash and the potential loss of lives. The chemicals involved in this demand for sleep are quite powerful and tend to override other chemicals that help to keep us awake.
It is also the case that when these chemicals are not present, it is very difficult to fall asleep. Our brain is doing a very good job of sustaining our vigilance and consciousness – even though we wish this were not so. We can do a few things to at least temporarily “trick” our mind (and body) into staying awake, whether this be ingesting caffeine or thinking about something that is filled with anxiety (what Robert Sapolsky describes as the human’s ability to imagine attacking lions in the form of financial, work-related, family-related, etc. fears and apprehensions). Neither of these alternatives is very attractive or healthy over the long term. There should be other ways to stay awake – or we should attend to our brain’s demands that we get some sleep.
Why Do We Need Sleep?
The benefits offered by sleep tend to circle around three important perspectives: (1) homeostatic regulation, (2) restoration and repair of bodily functions, and (3) storage and adjustment of mental functions. While these three perspectives are closely related, they do seem to arise from somewhat different sources of concern and interest. To borrow from an old adage, sleep is the elephant, but some of the blind men are touching the trunk, while others seem to be focusing on one of the elephant’s legs. If you put together all of their limited perspectives, then you get an accurate sense and picture about the whole elephant.
First, the homeostatic perspective. This is the most general perspective – and it relates directly to the demands being made by the brain. Our entire body is devoted on an ongoing basis to remain in some balanced state. We don’t want to be too warm or too cold and we don’t want to be too active or too sedentary. Most importantly, we want to balance off the time we are alert and active with the time we are inactive and restorative. There is a rhythm to our daily life (that I will describe shortly) and this rhythm results in a cycle requiring a period of sleep. If we don’t get enough sleep, then there is a sleep debt that accumulates—requiring that we fall asleep. This is the demand being made by our brain.