What Happens When You’re Sleeping?


Despite its elusive nature, sleep is one of the most vital human activities, and it plays a crucial role in mental and physical health. Researchers spend much of their time trying to understand what exactly happens when you’re asleep, and it turns out that it’s a lot more complex than we thought.

Sleep is a natural state of reduced activity, marked by decreased muscle activity and limited interaction with the environment. It’s also characterized by altered brain activity, including increased concentration in areas that regulate emotions. There are two phases of sleep: a deactivated state known as non-rapid eye movement, or NREM, and an active state known as rapid eye movement, or REM. It’s been long held that these states are distinct and separate, but recent data from brain-imaging studies suggests they are more complicated than that.

Researchers have several theories as to why we need sleep. The energy conservation theory suggests that sleep evolved as a way to conserve the body’s resources, especially since it would be harder to find food at night. The restorative theory argues that sleep is needed to feel refreshed in the morning and to repair cells and tissues that are used or damaged during the day.

There is also a strong link between sleep and memory. While you’re sleeping, the brain converts short-term memories into long-term ones and clears out old, unneeded information from the nervous system. Getting plenty of sleep can help you learn and remember new information, and it can also improve your ability to concentrate and focus during the day.

Another important function of sleep is to support the body’s immune system. During a period of sleep called non-rapid eye movement, the body produces antibodies that can fight off germs and viruses and help you heal after illness or injury. Insufficient sleep can lead to weakened immune systems, which increases your chances of getting sick with common infections like the cold or flu.

Sleep also benefits the body’s metabolism. Research has shown that adults who get adequate amounts of sleep are less likely to be overweight than those who do not. This may be because getting enough sleep reduces appetite and increases the production of leptin, a hormone that suppresses hunger. Combined with a healthy diet and regular exercise, consistent sleep can help people maintain a healthy weight and reduce their risk of heart disease.

Sleep can also boost the effectiveness of certain medications, and it can ease chronic pain. For example, in a phase of sleep called non-rapid eye movements, the brain sends signals to increase blood flow to muscles and to promote tissue growth and repair. This process is believed to be important in healing injuries and easing chronic pain, such as that associated with arthritis or back problems. Researchers are examining whether adding adequate sleep to the American Heart Association’s “Life’s Simple 7” of cardiovascular risk factors (such as smoking, exercise, cholesterol, blood pressure and blood sugar) can help lower the risk of heart disease even further.