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Book

Physiology of Sleep

Joshua E. Brinkman  1 , Vamsi Reddy  2 , Sandeep Sharma  3
In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan.
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Affiliations
Book

Physiology of Sleep

Joshua E. Brinkman et al.

Excerpt

Sleep is an extremely complicated process that consists of more than simply closing one’s eyelids and counting sheep. It is an active state of unconsciousness produced by the body where the brain is in a relative state of rest and is reactive primarily to internal stimulus. The exact purpose of sleep has not been fully elucidated. Several prominent theories have explored the brain and attempt to identify a purpose for why we sleep, which includes the Inactivity theory, Energy conservation theory, Restoration theory, and the Brain plasticity theory.

Inactivity theory is based on the concept of evolutionary pressure where creatures inactive at night were less likely to die from the predation of injury in the dark, thus creating an evolutionary and reproductive benefit to being inactive at night.

Energy conservation theory posits that the main function of sleep is to reduce a person's energy demand during part of the day and night when it is least efficient to hunt for food. This theory is supported by the fact that the body has decreased metabolism by up to 10% during sleep.

The restorative theory states that sleep allows for the body to repair and replete cellular components necessary for biological functions that become depleted throughout an awake day. This is backed by the findings many functions in the body such as muscle repair, tissue growth, protein synthesis, and release of many of the important hormones for growth occur primarily during sleep.

Brain plasticity theory is that sleep is necessary for neural reorganization and growth of the brain’s structure and function. It is clear that sleep plays a role in the development of the brain in infants and children and explains why infants must sleep upwards of 14 hours per day.

These theories are not exhaustive or all-inclusive of the prevalent ideas; rather, they serve to frame the concept that we do not fully understand sleep yet. It is more accepted that no single theory explains it all, and a combination of these ideas is more likely to hold the key to sleep.

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Conflict of interest statement

Disclosure: Joshua Brinkman declares no relevant financial relationships with ineligible companies.

Disclosure: Vamsi Reddy declares no relevant financial relationships with ineligible companies.

Disclosure: Sandeep Sharma declares no relevant financial relationships with ineligible companies.

References

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