Why We Sleep: Mechanics

Note: As an aside, you may notice that this is not the same book that was referenced in the previous two blog posts — this will probably be pretty typical in this blog post for the sole reason that I enjoy reading multiple books at a time. Increasing cognitive strain on recall has been shown to improve retention of information, which can be increased by interleaving different sources of information at a given time. This, however, must be taken with a grain of salt, since I don’t think doing so on a micro scale has the same benefits. Namely, switching between reading books in quick succession, i.e. after a chapter of each, doesn’t allow attention to gain enough traction in either one of the sources, thus preventing it from being moved into short-term memory in the first place. With that aside out of the way, let’s move into the actual material.

Sleep has, for the most part, been seen as the antithesis of productivity. After all, look at people the media, or even our parents esteem: they boast about how little they sleep in lieu of getting more done during the day. Or so they say. Take Elon Musk or anyone working in IB (investment banking) for example: these are some figures that pop up very regularly in such discussions. However, sleep has been shown to hold tremendous benefits and its deprivation tremendous repercussions, which is the main focus of this book.

Let’s start with looking at what sleep actually is. Most of us are aware of its description on a cursory level: we lie down and lose consciousness. But, even before that, this discussion begs the question, why do we feel the need to sleep? This comes, somewhat with surprise, as the result of two main factors.

The first is the circadian rhythm. This is the “internal clock” that all organisms seem to possess that seems to naturally resonate approximately with the 24 hour day cycle. In reality, it is slightly more (24 hours and 15 minutes). All organisms are surprisingly equipped with said cycle, which was initially discovered through a plant-based experiment. A certain type of plant possesses leaves that curl during nighttime. It is natural to assume this is simply something that results from the lack of sunlight hitting its leaves. However, the scientist responsible put the plant in a fully enclosed box devoid of sunlight. In the process, the plant continued to exhibit this behavior as if the sun were rising and setting as normal, concluding that the plant itself must be maintaining a cycle that dictates this behavior.

In a similar fashion, two scientists went into a cave to test the theory on human sleep cycles. They found that people, even in the lack of sunlight, maintain a consistent sleep pattern, the heart of which is the circadian rhythm that we have.

In addition, there is a chemical called adenosine whose buildup causes drowsiness over the day. This chemical is released continuously over the day and is flushed out from the brain during sleep. Adenosine is only flushed out upon sleep and is continuously produced, whereas the circadian rhythm continues regardless of a person’s engagement in sleep. However, it is not the absolute amount of adenosine that causes sleep. It is, instead, something called the “sleep gate,” which measures the overlap between the adenosine buildup and circadian rhythm, as illustrated below.

Image result for S and C curve sleep

While the y-axis on this graph is ambiguous and probably has no actual meaning, this figure perfectly illustrates how sleepiness works. One very convincing argument to see that it is, in fact, two separate phenomena that work in conjunction is the following. Since the circadian rhythm continues regardless of a person sleeping whereas adenosine buildup is continual until sleep, after pulling an all-nighter, people typically experience a “second wind,” where the circadian rhythm is in its high state despite the adenosine buildup being considerably higher than normal. The apparent lack of disparity between the two is what leads people to feel not as tired as they may expect to feel. However, that night will be an enormous gap and, hence, an incredibly strong sense of drowsiness.

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