Circadian Rhythms and Your Sleep
We have two internal systems that govern our sleepiness and wakefulness. One is a circadian process, which occurs on a daily –ish rhythm and the other is a sleep- wake homeostatic process.
Many of our physical and mental processes occur in roughly-24-hour cycles, driven by what are called circadian rhythms. These rhythms help determine our sleepiness and wakefulness and are triggered by an internal clock inside our brains, more formally known as the suprachiasmatic nucleus, or SCN. The SCN is super-important and controls many bodily systems, like eating, blood pressure, temperature, and when we want to sleep and be awake.
Sleep-Wake Homeostasis is the second process that influences our sleepiness and wakefulness. It produces a drive or pressure to sleep the longer we’ve been awake. Feelings of sleepiness correlate to our levels of Adenosine which rise throughout the day and then are lowered while we sleep. The higher your adenosine levels, the more you want to sleep.
Caffeine temporarily blocks the effect of rising Adenosine levels making you feel more alert and awake. However, when our bodies rid the effects of caffeine we experience the effects of all the built-up Andeonsine at once.
Understanding these systems illustrates how our need for sleep is not a character flaw — it’s how we are wired. Knowing how sleep works helps us appreciate how factors like light-exposure and shift-work, diet, and other behaviours can be detrimental to our sleep and helps point the way to strategies that help us own the night, and seize the day.