Usually sleepers pass through five stages: 1, 2, 3, 4 and REM (rapid eye movement) sleep. These stages progress cyclically from 1 through. Stage 1 of non-rapid eye movement sleep (NREM), or dreamless sleep, occurs after When NREM Stage 2 sleep kicks in, things get serious!. Stage 2 is the second stage of sleep and lasts for approximately 20 minutes. The brain begins to produce bursts of rapid, rhythmic brain wave.
Sleep Stage 2
Sleep spindles engage brain activation in the superior temporal gyri, anterior cingulate, insular cortices and the thalamus. Sleep spindles have different lengths; with slow spindles associated with an increase in activity in the area known as the superior frontal gyrus ranging between 11 and 13 Hz, and fast spindles associated with the recruitment of both the hippocampus and the mesial frontal cortex and the sensorimotor processing cortical regions ranging between 13 and 15 Hz.
K-Complexes are also exclusive to NREM sleep, and can be defined as single long delta waves lasting for only a second. Like sleep spindles, they appear automatically during the early stages of sleep, generally in stage two.
However, K-Complexes can be induced at will by momentary noises, such as someone knocking on a door. Further research must be conducted on K-Complexes because their function is currently unknown. During REM sleep, study participants reported both intense dream vividness and improved memory of dreams which occurred during that phase, which suggests that dreaming typically occurs REM sleep: We also know that dreams that occur during the NREM stage of sleep typically occur after midnight, which happens to be the time-period with the highest rate of REM sleep.
This was discovered by a study whereby subjects took naps over specific periods of time and were then forcefully woken: The diaphragm is typically driven by the autonomous system and is therefore normally spared non-REM inhibition, and as such, the suction pressure generated stays the same.
The upper airway is thus narrowed during sleep, which increases resistance and makes upper airway airflow noisy and turbulent. As we know, we determine that a person is asleep by listening to their breathing: For overweight people, this problem is aggravated when they sleep on their back because excess fat tissue can easily push down and close the airway.
This can ultimately lead to sleep apnea. Each sleep stage serves a unique role in brain and body restoration. There are many sleep deprivation studies that have demonstrated that depriving subjects of specific sleep stages has an adverse effect on body and brain functions. Notify me of new posts by email.
Stages of Sleep There are five stages of sleep. Stage 2 Sleep Stage 2 usually follow Stage 1 and represents deeper sleep. However, sleep is an active state that affects both your physical and mental well-being. A good night's sleep is often the best way to help you cope with stress, solve problems, or recover from illness. Sleep is prompted by natural cycles of activity in the brain and consists of two basic states: Vivid dreams tend to occur during REM sleep. Usually, REM sleep occurs 90 minutes after sleep onset.
The first period of REM typically lasts 10 minutes, with each recurring REM stage lengthening, and the final one lasting an hour. Polysomnograms sleep readings show wave patterns in REM to be similar to stage 1 sleep. In people without sleep disorders, heart rate and respiration speed up and become erratic during REM sleep. The face, fingers, and legs might twitch. Intense dreaming occurs during REM sleep as a result of heightened cerebral activity, but paralysis occurs simultaneously in the major voluntary muscle groups.
REM is a mixture of encephalic brain states of excitement and muscular immobility. For this reason, it is sometimes called paradoxical sleep. The percentage of REM sleep is highest during infancy and early childhood. During adolescence and young adulthood, the percentage of REM sleep declines, and the percentage decreases further in older age. Brain waves during Stage 3 are called delta waves due to the slow speed and large amplitude.
Of all of the sleep stages, Stage 3 is the most restorative and the sleep stage least likely to be affected by external stimuli. Waking a person from deep sleep can be difficult. Following a period of sleep deprivation , a person experiences extensive time in Stage 3 sleep. Parasomnias such as sleep walking, sleep talking, night terrors and bedwetting can occur.
Deep sleep reduces your sleep drive, and provides the most restorative sleep of all the sleep stages. But if you take a nap long enough to fall into deep sleep, you have more difficulty falling asleep at night because you reduced your need for sleep. During deep sleep, human growth hormone is released and restores your body and muscles from the stresses of the day.
Your immune system also restores itself. Much less is known about deep sleep than REM sleep. It may be during this stage that the brain also refreshes itself for new learning the following day. The first half for a majority of people consists mostly of Stages 2 and 3 with sporadic periods of Stage 1 and short REM periods.
As the night progresses, Stage 3 begins to diminish in quantity while Stages 1 and 2 remain with lengthening periods of REM occurring. A person typically experiences three to five REM periods throughout sleep time with the longest REM period right before awakening for the day.
If woken prematurely from completing the REM period a person can experience a period of sleep inertia whereby a heightened sensation of sleepiness can occur for several minutes or even several hours.
In the REM period , breathing becomes more rapid, irregular and shallow, eyes jerk rapidly and limb muscles are temporarily paralyzed. Brain waves during this stage increase to levels experienced when a person is awake. Also, heart rate increases, blood pressure rises, males develop erections and the body loses some of the ability to regulate its temperature.
As an active sleep state, REM is the time when the most vivid dreams occur. The rapid eye movements that occur can be seen as sharp, rapid movements. Brain waves during REM sleep are considered to be of low amplitude and mixed frequency consistent with higher activity than that seen in Stages 2 and 3.
A person may dream 4 to 6 times each night. A French study found that all people do in fact dream, whether they remember their dreams or not. However, if awoken during REM sleep, a person often can remember their dreams.
Muscle paralysis often accompanies REM sleep. This muscle atonia or muscle paralysis occurs as a protective means to keep one from acting out their dreams.
Obstructive Sleep Apnea is often the worst during REM periods due to the lack of muscle tone within the muscles of the airway. Scientists believe this may be to help prevent us from injury while trying to act out our dreams.
During REM respirations are irregular and shallow and irregularities in heart rate and body temperature also occur. As sleep research is still a relatively young field, scientists did not discover REM sleep until when new machines were developed to monitor brain activity. Before this discovery it was believed that most brain activity ceased during sleep.
Since then, scientists have also disproved the idea that deprivation of REM sleep can lead to insanity and have found that lack of REM sleep can alleviate clinical depression although they do not know why. Recent theories link REM sleep to learning and memory.
Natural Patterns of Sleep
Stage 2 non-REM sleep is a period of light sleep before you enter deeper sleep. Your heartbeat and breathing slow, and muscles. Stage 1: Your eyes are closed, but it's easy to wake you up. This phase may last for 5 to 10 minutes. Stage 2: You are in light sleep. Your heart. NREM sleep can be broken down into three distinct stages: N1, N2, and N3. In the progression from stage N1 to N3, brain waves become.