For most people, the word “sleep” conjures up peace and relaxation after a long day. However, your body undergoes many changes during the hours that you are unconscious. From undoing the day’s harm to preparing for the day ahead, the human body is constantly sorting, repairing, and refreshing. So next time you wake up feeling like a different person, know that there may be some truth to the thought.
10. Filing Away Memories
Human beings are very active organisms. We do things, go places, and interact with people, all the while creating memories. Memories are stored in the brain. But as anybody who has ever tried to find a file on a crowded desktop knows, saved things are of no use if they cannot be easily accessed and found.
During sleep, the brain actually replays the day’s events, catalogs them, and stores them in the brain’s long-term memory centers. Simultaneously, the brain discards unnecessary memories.
This storing of important long-term memories is critical to humans being able to function properly. This is because long-term memory is essentially limitless and set in stone, meaning that these memories will stay with you for your lifetime.
Most people can remember specific memories from their childhood very vividly but have a much harder time remembering exactly what they did two days ago. This kind of memory prioritization is essential for learning and retaining information as well as developing skills like problem-solving or mastery of a sport or game.
Most of this memory consolidation occurs during one of the deepest parts of sleep, slow-wave sleep, in which there is little other brain activity. As the mind transitions into REM (rapid eye movement) sleep, the brain then stabilizes the critical memories for quick recall later.
9. Blood Pressure And Core Temperature Drop
About 30 minutes before you fall asleep, the body begins to lower its body temperature. This occurs to slow down your metabolism to the point where you can sleep for hours without going hungry. As a result, heart rate and blood pressure also decrease.
While this may not seem like a big deal, your core body temperature drops by more than 1.1 degrees Celsius (2 °F) to around 35.6 degrees Celsius (96 °F), which is one degree above hypothermia. Your body also needs less energy, so you are in no danger of freezing to death while taking a nap.
Upon waking up, blood pressure and heart rate rapidly rise again to keep up with the demand for energy. But for a brief period of time, there is an imbalance, resulting in the sluggishness and clouded thinking experienced by people who have just awakened.
Ever had a nightmare and found you couldn’t run or scream? While this can be terrifying, this phenomenon (known as “sleep paralysis”) is what keeps you from acting out all your dreams in real life (which is probably a good thing). During REM sleep in which dreams occur, the brain blocks neurotransmitters and receptors in muscles, effectively paralyzing you.
Occasionally, this can happen briefly when falling asleep or waking up, during which you are fully conscious but unable to move at all. This state is quite terrifying.
It is also the root of many ancient legends, usually involving hallucinations. In these legends, people are visited by demons or other creatures (from the Old Hag in Anglo-Saxon tradition to the “Pinyin” in Chinese folklore) and are unable to move.