Why Do I Sleep?
- The Little Physio
- May 3, 2019
- 3 min read
Sleep is a behaviour that takes up about a third of our day. We feel like we need it after extensive travelling, physical exertion or mental exertion with the aim of making us feel refreshed and energetic for the next day’s tasks.
In this day and age, it almost seems too common to hear people struggling to sleep. In the media, we always here about how important it is to sleep and why we should sleep 7-8 hours per day. So, why do we actually sleep?
Fortunately, there are a few theories behind why we sleep?
Adaptive behaviour
The first one is in relation to evolution and is termed the adaptive theory. This theory suggests sleep has evolved as a way to reduce activity during times when predators are out roaming. Thus, sleeping during active predator times protects your genetic lineage from predation. However, this is counteracted by the argument about how people would then be unable to defend themselves from predators if they are unconscious.
When I mentioned this to my partner, an evolutionary biologist, he said it is not uncommon for those within a tribe to have different sleep patterns where the different sleep-wake cycles allows ‘predator lookout’ shifts to be taken effectively. This means people are able to sleep when they need it and remain protected from predators.
Conservation of energy
The second theory is about conservation of energy. Sleep has evolved as a behaviour to conserve energy at a time where foraging and hunting for food is more difficult. It is suggested that mammals can decrease their metabolic rate by 15-30 percent, equating to 5-9 percent of energy being saved per day with an average of 8 hours of sleep. However, contrary to this notion, during sleep some biological processes are upregulated. For example, protein synthesis, cellular repair, immune system function, eliminating waste or reorganising the brain for learning and memory. Therefore, sleep may be a time where one can strategically decrease some metabolic processes, whilst rediverting energy to other physiological functions which cannot be attended to during the day.
Restorative process
Thirdly, sleep can also be a time where what has been depleted and used up during waking hours is restored.
Sleep, therefore, serves as a restorative activity for the body’s function.
This ties in very closely to the conservation of energy theory as restorative processes are upregulated during sleep.
Neuroplasticity
The final theory revolves around brain neuroplasticity. Neuroplasticity describes the ability of the brain to change by laying down and forming new neural connections or networks. New neural connections can be formed, for example, when we learn a new skill, such as mindfulness or a new language.
The importance of sleep for neural function is highlighted in cases of chronic sleep deprivation. The negative neural effects include an increase in cellular stress and increase in regulated cell death genes, degeneration of neurons usually active in the wake cycle, increased neural inflammation and suppression of neurogenesis. Sleep, thus, is important for neuroplastic processes such as learning, memory and cognition. And these indeed are adversely affected by sleep deprivation.
In summary, sleep is something we all seem to need more. Our body seeks out sleep for restorative processes for the brain and body, and is also important for how we learn and and lay down memories. When you are next wake up from a nap or night’s sleep, thank your body for working away during the night to allow you to explore your world with energy and delight.
Thanks for reading and I wish you a restorative sleep (or sleeps)!
Resources for further information
Neuroplasticity
Sleep articles
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