Sleep is an essential aspect of maintaining good health and ensuring proper functioning of the human body. Contrary to popular belief, sleep is not a passive state where the brain shuts down to rest. In fact, the brain remains actively engaged during sleep, and its activity may even surpass that of waking hours. The sleep cycle is a series of distinct phases that collectively contribute to the overall sleep experience. Each cycle typically lasts between one and two hours and involves two main phases – rapid-eye-movement (REM) and non-rapid-eye-movement (NREM) phases.
Sleep Patterns and Brain Activity
Scientists and researchers studying sleep have made interesting discoveries about the different processes that occur during different stages of sleep. By using electroencephalography (EEG) to monitor brain waves, they have found that brain activity fluctuates throughout the night. One particular type of brain wave activity, known as delta waves, exhibits significant variability.
Alongside the changes in delta wave activity, certain bodily functions also undergo alterations. For instance, during NREM sleep, when delta wave activity increases, the secretion of hormones responsible for lactation, blood pressure regulation, and growth also increase. On the other hand, during periods of decreased delta wave activity, such as the REM phase, there is an increase in the secretion of thyroid-stimulating hormone and heart rate variability.
Rapid-Eye-Movement (REM)
The REM stage, also known as paradoxical or active sleep, is a fascinating phase characterized by frequent eye movement. It is the easiest stage to wake from and is the time when dreams occur. During this phase, respiration can accelerate, and brain activity can increase, resembling wakefulness. Interestingly, the muscles in the arms and legs become less responsive or even temporarily paralyzed to prevent the body from acting out dreams. As we sleep for longer durations, the number of REM cycles we experience increases.