The Importance of Sleep
Sleep is one of the most mysterious and vital aspects of human life. It affects almost every cell and system in the body, including the brain, heart, lungs, immune system, metabolism and mood. It’s no wonder that people who regularly miss out on the quality of their sleep are at increased risk for disorders such as depression, high blood pressure and obesity.
Scientists spend a lot of time studying sleep because it is so crucial to our mental and physical health. They’re discovering that sleep does much more than simply make us feel rested. During the hours we spend in bed, our muscles repair themselves and our brains sweep away waste, and our bodies release hormones that play important roles in everything from how we react to stress to how we fight off disease.
We need sleep to survive, but researchers are just beginning to understand why that is. The answers might be as simple as it gets: sleep is necessary to prepare the brain for learning, remembering and creating, and to help the body heal itself from the daily wear and tear of the world around us.
Most scientists agree that we have evolved with a natural drive for sleep. Our bodies and brains develop a need for it just as our bodies hunger for food throughout the day. When that need reaches a certain point, it is time to go to sleep.
Researchers also believe that the brain has a built-in clock that regulates how long we sleep, and is influenced by various environmental factors such as light, noise and food availability. These circadian rhythms are the foundation for the bodily cycles that govern growth, reproduction and aging.
Scientists have been able to recognize sleep in animals by observing periods of quiescence, reduced sensitivity to sensory stimuli and the stereotypical posture of recumbent rest. These behavioral traits are broadly conserved across different species, and they are reliable indicators of sleep in invertebrates (cockroaches, bees, fruit flies, etc) and vertebrates (humans).
While sleeping, the brain shifts from the thalamus – which processes the signals sent to it by our senses – to the cerebral cortex, which interprets the information and converts it into short- and long-term memory. As we fall into deeper stages of sleep, this process slows down even further. During REM sleep, the thalamus remains active, sending messages to the cortex that create the images and sounds of dreams.
During these deeper phases of sleep, the body releases growth hormone, which is essential for tissue and muscle growth. This is important for repairing the damage from daily wear and tear, as well as promoting muscle recovery after exercise. It also reduces inflammation and the production of stress hormones that contribute to chronic inflammatory conditions such as arthritis, asthma and diabetes.
During this time, the brain is also busy converting short-term memories into long-term ones and clearing away cellular and protein debris that can cause inflammation and cancer. It is during this phase that many of our biggest discoveries have been made, such as the discovery that the brain has a drainage system that removes toxins twice as quickly as during wakefulness.