Sleep is an important part of your daily life – you spend about a third of your time doing it. Good sleep – get enough sleep at the right time – essential for food and water survival. Without sleep, you can’t form or maintain pathways in your brain, let you learn and create new memories, and it’s harder to focus and react quickly.
Sleep is important for many brain functions, including how nerve cells (neurons) communicate with each other. In fact, your brain and body stay very active while you sleep. Recent research has shown that sleep acts as a housekeeper and removes toxins from the brain that accumulate when you are awake.
Everyone needs to sleep, but its biological purpose is still a mystery. Sleep affects almost all types of tissues and systems in the body – from the brain, heart and lungs to metabolism, immune function, mood and disease resistance. Studies have shown that long-term lack of sleep or poor sleep quality increases the risk of high blood pressure, cardiovascular disease, diabetes, depression and obesity.
Sleep is a complex and dynamic process that affects how scientists now begin to understand. This booklet describes how your sleep needs are regulated and what happens in your brain during sleep.
There are two basic types of sleep: rapid eye movement (REM) sleep and non-rapid eye movement sleep (in three different stages). Each is associated with specific brain waves and neuronal activity. On a typical night, you can cycle several times in all phases of non-REM and REM sleep, and in the morning there is a longer, deeper REM cycle.
Stage 1 non-REM sleep is a shift from awakening to sleep. During this relatively light sleep (for a few minutes), your heartbeat, breathing and eye movements slow down and your muscles relax during occasional convulsions. Your brainwaves start to slow down from the awake mode during the day.
Stage 2 non-REM sleep is a mild sleep before entering deep sleep. Your heartbeat and breathing are slow and your muscles are further relaxed. Your body temperature drops and your eye movements stop. Brainwave activity slows but is characterized by transient electrical activity. In Stage 2 sleep, you spend more repetitive sleep cycles than other sleep stages.
Stage 3 non-REM sleep is a deep sleep period that you need to feel refreshed in the morning. It happened in the longer period of the last half of the night. Your heartbeat and breathing will be reduced to a minimum when you sleep. Your muscles are very relaxed and it may be difficult to wake you up. Brain waves become slower.
REM sleep first occurs about 90 minutes after sleep. Your eyes move quickly from one side to the other behind the closed eyelids. Mixed-frequency brainwave activity becomes closer to what is seen in waking. Your breathing becomes faster and more irregular, and your heart rate and blood pressure increase to near-awake levels. Most of your dreams occur during REM sleep, although some may occur in non-REM sleep. Your arm and leg muscles are temporarily paralyzed, which will prevent you from showing your dreams. As you get older, your sleep time in REM sleep will decrease. Memory integration is most likely to require non-REM and REM sleep.