Sleep Science: The Phases of Sleep

There are many professionals out there that study sleep science; the phases of sleep, the effects of sleep, dreams, and even pillows and mattresses and how those affect our sleep patterns. Sleep is extremely important, though we sometimes put it on the back burner.

Let’s talk today a little about sleep phases.

Sleep is a physiological state necessary for all life forms. It is characterized by a temporary pause in movement and senses. During sleep, there are changes in the functions of the body and brain activity that is essential to both the physical and psychological balance of the human being.

There are two stages of sleep, the first called NO REM, and the second REM. REM stands for Rapid Eye Movements. NO REM sleep is divided into four phases. Each one has distinct characteristics.

Here’s how they work:

Phase 1: NO REM – when we are still capable of perceiving most of what is going on around us. It is not reparative. They eye movements are slow.

Phase 2: In this phase, the nervous system blocks the brain’s access to sensory information, which creates a disconnect between us and our environment and allows us to sleep. This phase is partially reparative, but not completely. This phase occupies around 50% of the sleep time of an adult. There are no eye movements.

Phase 3: This is a more profound sleep, sometimes called DELTA. The sensorial block is even stronger, and if we happen to wake up during this phase, we feel confused or disoriented. In this phase, we do not dream, our blood pressure drops 10 to 30 percent and the human growth hormone production increases. There are no eye movements.

Phase 4: This is the deepest sleep, in which brain activity is slower. Like phase three, it’s essential for our physical and mental repair. In this phase, we don’t normally dream, however, nightmares may appear.

Phase 5: REM – In this phase the central nervous system is reactivated, we dream, and our muscles are paralyzed in order to prevent us from doing ourselves harm.