Biologically, sleep is a period when the brain is engaged in life-sustaining activities such as restorative processes. It is also an important period of reorganization of neurons in the brain. Sleep also plays an important role in physical and mental health. It plays a role in metabolism, a process that uses energy to maintain the body. Sleep also helps the body repair itself and recover from illness. Obtaining a good night’s sleep can be a lifesaver. Getting enough sleep is important for mental and physical health, and not getting enough sleep can increase the risk of several illnesses.
Sleep is not a simple state, but is generally defined by a combination of physiological, motor, and sensory criteria. Some criteria may be absent in the case of sleepwalking. Typically, agreement among observers is needed to distinguish between sleep and wakefulness. Sleep is also accompanied by a number of electroencephalogram (EEG) patterns, which are brain patterns of electrical activity.
In some animals, there are two distinct phases of sleep. The first is rapid eye movement (REM) sleep, in which dreams are frequently experienced. This phase of sleep can last 5 to 15 minutes. The second is non-REM sleep, which is usually referred to as a single phase. The EEG patterns in this phase are superficially similar to drowsiness, but are not always useful in discriminating between sleep and wakefulness. The REM phase is followed by the slow wave sleep phase, which is a much more deeply deactivated state.
In animals, sleep is characterized by a posture of horizontal repose. This posture is also found in humans. This characteristic posture is believed to be a result of the skeletal muscles being relaxed, as they are asleep.
Other mammals exhibit periodic periods of inactivity, similar to sleep. During this period, they may search for food and water. These periods are characterized by low critical reactivity, which may be indicative of the need for a protective response. Sleep also appears to be important in the development of the brain. The glymphatic system helps the brain clear out toxic byproducts from the central nervous system.
Sleep also plays a role in the brain’s ability to learn. It allows the brain to consolidate memories, which can make learning new things easier. Sleep is also known to increase a person’s ability to handle stress. Not getting enough sleep increases symptoms of high blood pressure, depression, and migraines. Not getting enough sleep can also affect the immune system, which can cause infections. It is estimated that a single night’s missed sleep can lead to a prediabetic state.
Sleep is not a simple state, and there is much more to know about the physiology of sleep than can be found in a single study. There are several theories about sleep, including the brain plasticity theory, which states that the body needs sleep in order to recover from the stress of a day’s work. A recent Natural Neuroscience study indicates that the brain is capable of learning new behaviors while asleep.