Stages of Sleep
Much has been learned in the last century about the different stages of sleep. Basically, when we sleep, we have both Non-Rem sleep (Stage 1, Stage 2, Stage 3) and Rem sleep. Non-REM sleep happens in three different stages of sleep:
In Stage 1, you are more easily awakened, even if your eyes are closed and you are actually asleep. There is about a 5-10 minute window in which we are in this stage of non-REM sleep.
In Stage 2, your heart rate decreases and your body temperature lowers. You are in a light sleep; however, it is a precursor to going into the deepest stages of sleep.
In Stage 3, you are in the deepest kind of sleep. It is the hardest to arouse you when you are in this stage of sleep. If you are awakened during this stages of sleep, you will often feel disoriented for a brief time after you awaken. Dreams are possible but uncommon during non-REM sleep.
Non-REM sleep is important for body repair and growing. You build strength to your immune system while in this stage of sleep and your body repairs itself. Children do much of their cellular growing during non-REM sleep.
REM stands for “rapid eye movement” and is a time when we can actually see our eyelids fluttering during a dream. Rem sleep is called paradoxical sleep because during REM sleep, our brain wave patterns mimic those of the awakened state. Our heart rate increases, our breathing rate increases and our eyes flutter. Women have an increase in sexual sensitivity and men can have erections during REM sleep. We first go into REM sleep about 70-90 minutes after initially falling to sleep. During this period, our mind creates actual, yet fanciful dreams spun only by our unconscious imagination.
After REM sleep, we go into non-REM sleep—a deeper state of sleep when the delta waves are more active. We can dream but the quality of the dreams is different from those in REM sleep. A total sleep cycle lasts about 90-110 minutes and is divided into REM states and non-REM states of sleeping. We have several of these sleep cycles during any given night. The REM states tend to be of a longer duration as the night passes, while the length of the non-REM states decreases. The early morning sleep cycle consists mostly of REM sleeping and we remember these dreams if we awaken during the night with them or first thing in the morning, just after arising.
Do You Dream in Rem Sleep?
Rem Sleep is the state of sleep when we are most likely to dream. In total, we spend about 2 hours during the night having dreams. No one knows the exact function of dreams, yet some dreams seem to represent the brain/mind trying to make sense out of the activities of the day or solve problems in our lives. Even babies are shown by an EEG to have dreams. Mammals and other higher order animals have dreams, too. REM sleep seems to originate in the pons, a part of the basal area of the brain. The signals then travel to the thalamus, which is part of the brain that connects the basal/primal areas of the brain to the higher, cortical part of the brain (the areas in which we think). While the brain is dreaming, the pons shuts off our spinal cord so we don’t act out our dreams through movement.
Rem Sleep Behavior Disorder
People with REM sleep behavior disorder have a problem shutting off their bodily movements during REM sleep and they can physically act out their dreams while sleeping—something that can be very dangerous and debilitating, depending on the dream.
Why is Rem Sleep Important
REM Sleep is important because it stimulates the learning centers of the brain. Because babies have more REM sleep than adults, it is felt they are learning things at a much more rapid rate than adults. The content of the dreams can be anything. While psychologists try to interpret the meaning of dreams, they may just represent random electrical firings from the cerebral cortex that is integrated into a “story” that makes at least some sense.
Every day, we go through a series of mental and physical changes that together form our circadian rhythm. The circadian rhythm is our biological clock that is pre-set in our brain, and is determined by areas of our hypothalamus and pineal gland. During the circadian rhythm of a single day, there are hormonal changes that affect the immune system, such as changes in our body’s cortisol level; there are times of wakefulness and times of sleep. The suprachiasmic nucleus within the hypothalamus is the part of the brain that helps determine when we sleep, our hormone levels, our body temperature, our urine production and our blood pressure during the day and night.
Why Circadian Rhythm
No one knows exactly how and why this circadian rhythm has been set up but, when we try to go against our circadian rhythm, such as with night shift work and jet lag, we can become very tired when we are not supposed to be or be wide awake when the circadian rhythm is trying to override the external cues in our environment that tell us it is time to sleep.
Brain Waves During Awake
When we are awake, our brain has erratic and unpredictable brain wave patterns. This represents the electrical activity going on while we are thinking, alert, and doing something during the day. Even if you lie down and pretend to go to sleep, your brain wave pattern will give you away as the brain wave activity will not show you are sleeping.
During much of the waking period, our brains are emitting beta waves. This is the alert state and they occur more commonly when we are nervous, agitated, or fearful of something. We can, through practice, get into the alpha wave mode. When we are exhibiting alpha waves on the EEG, we are physically and mentally relaxed. This is a time when we are most able to learn new things. Theta waves are even slower. We have a reduced level of consciousness and are nearly asleep or in the beginning stages of sleep. Delta waves are the slowest kind of brain waves. When we are in the delta stage of sleep, we are in a deep sleep and are generally not dreaming.