Sleep Stages PDF

How do we measure this?  Much of our knowledge of what happens during sleep comes from the electroencephalogram – We're just going to call this the EEG: a machine that measures electrical activity in the brain.  When probes from the EEG machine are attached to the surface of a sleeping person's sc...

How do we measure this?  Much of our knowledge of what happens during sleep comes from the electroencephalogram – We're just going to call this the EEG: a machine that measures electrical activity in the brain.  When probes from the EEG machine are attached to the surface of a sleeping person's scalp and face, it becomes clear that the brain is active throughout the night.  It produces electrical discharges with systematic, wavelike patterns that change in height (or amplitude) and speed (or frequency) in regular sequences.  People progress through 5 distinct stages of sleep during the night (each with their own brain wave patterns). Stage 1 through 4 and REM sleep – moving through the stages in cycles lasting 90 minutes. Hypnagogic State  To enter the first stage of sleep, we must first get to sleep. We call it falling asleep, but Psychologists refer to this phase of pre-sleep consciousness as the hypnagogic state.  Some people experience vivid images called hypnagogic image during this period.  Others can experience a "hypnic jerk" which is a feeling of falling or uncontrolled muscle spasm. Stage 1 Sleep  When people fall asleep, they move from a relaxed waking state with their eyes closed into stage 1 sleep, which is characterized by relatively rapid, lowamplitude brain waves.  Stage 1 serves as a transition between wakefulness and sleep and lasts only a few minutes. During stage 1, images sometimes appear, as if we were viewing still photos. However, this is not considered dreaming. Stage 2 Sleep  As sleep becomes deeper, we enter stage 2 sleep.  Stage 2 sleep makes up about half of the total sleep of those in their early twenties, and is characterized by a slower, more regular wave pattern.  Despite the slower wave pattern, there are also momentary interruptions of sharply pointed spiky waves that are called sleep spindles. Additionally, when there is a large spike in the wave, it is known as a K-Complex  It becomes increasingly difficult to awaken a person from sleep as stage 2 progresses. Stage 3 Sleep  As people drift into stage 3 sleep, the brain waves become slower, with higher peaks and lower valleys in the wave pattern.  Stages 1-4 of sleep are known as non-REM sleep; in these stages we fall deeper and deeper into sleep until reaching REM sleep Stage 4 Sleep  Stage 4 sleep, which is the deepest stage of sleep, is most likely to occur during the early part of the night.  Stages 3 and 4 have low frequency, high amplitude waves called Delta Waves. When are brain electricity is flowing in the form of these waves, we are getting the deepest and fullest rest.  In the first half of the night, sleep is dominated by stages 3 and 4. The second half is characterized by stages 1 and 2 - as well as a fifth stage, REM Sleep, during which dreams occur. REM sleep  Several times at night, when sleeps have cycled back to a shallower state of sleep, something strange starts to happen. Our eyes although not open, move back and forth as if we are watching an action filled movie.  This period of sleep is called rapid eye movement (REM) Sleep. This contrasts with Sleep stages 1-4 which are collectively labelled as non-REM or NREM sleep. REM sleep occupies a little over 20% of adults sleeping time. REM sleep  REM sleep is usually accompanied by dreams. Although some dreaming occurs in the non-REM stages of sleep, dreams are most vivid and easily remembered from REM sleep.  REM may also play a role on learning and memory, allowing us to rethink and process information and emotional experiences that we’ve had during the day. Why Sleep is Necessary  Has anyone ever heard that “Sleep is for the weak”?  From an evolutionary perspective, sleep protected our ancestors from night-time predators and allowed them to conserve energy at night, when food was hard to come by.  From a modern perspective, sleep is needed to replenish our brain and body. The reduced activity of the brain in non-REM sleep can give neurons in the brain a chance to repair themselves.  In REM sleep, the release of certain neurotransmitters called monoamines is stopped in order to give receptor cells time to rest and be sharper and more sensitive during the day. Circadian Rhythms  The fact that we cycle back and forth between wakefulness and sleep is one example of the body’s circadian rhythms.  Circadian Rhythms are biological processes that occur regularly on approximately a 24-hour cycle. Sleeping and waking works in a cycle, as well as body temperature, hormone production, and blood pressure.  Circadian cycles are complex and involve a variety of behaviours. For example, sleepiness occurs not only at night but thought the day in regular patterns, with most of us getting drowsy in mid-afternoon. Many cultures take advantage of the body’s natural desire to sleep at this time. Circadian Rhythms The picture can't be display ed.  Circadian Rhythms are controlled by a part of the brain called the suprachiasmatic nucleus (SCN)  The suprachiasmatic nucleus is a bilateral structure located in the anterior (front) part of the hypothalamus. It is the central pacemaker of the circadian timing system and regulates most circadian rhythms in the body  The neuronal and hormonal activities it generates regulate many different body functions in a 24-hour cycle Hypnosis  Hypnosis is a psychological phenomenon that is controversial and heavily debated today.  People under hypnosis are in a trance-like state of heightened susceptibility to the suggestions of others. In some respects, it appears as if they are asleep.  Yet other aspects of their behaviour contradict this, for people are attentive to the hypnotists' suggestions and may carry out bizarre or silly suggestions.  Despite compliance while hypnotized, people do not lose all free will. They will not perform antisocial behaviours, or self-destructive acts. They will not reveal hidden truths, and they are still capable of lying. The picture can't be display ed. Hypnosis  There are wide variations in people’s susceptibility to hypnosis. 5%-20% of the world's population cannot be hypnotized, and 15% are easily hypnotized. Leaving about 65%-80% of the population in the grey area of possibility.  People who are hypnotized easily are also easily absorbed while reading books or listening to music, becoming unaware of what is happening around them, and can spend an unusual amount of time daydreaming. The picture can't be display ed. Hypnosis  The question of whether hypnosis is a state of consciousness that is different from normal waking consciousness is controversial.  Psychologist Ernest Hilgard argues that hypnosis represents a state of consciousness that differs significantly from other states.  He asserted that the states of higher suggestibility, increased ability to recall and construct images, and acceptance of suggestions that contradict reality are evidence in themselves.  Also, changed in the electrical activity of the brain support that hypnosis is a state of consciousness different form normal waking life. The picture can't be display ed. Value of Hypnosis  Hypnosis has been used to solve practical human problems, and is used by some psychologists and has even been successful. Hypnosis has been used in the following areas:  Controlling pain  Reducing smoking  Treating mental health  Assisting in law enforcement  Improving athletic performance.  So, what is your verdict? The picture can't be display ed. Meditation  Meditation is a learned technique for refocusing attention that brings about an altered state of consciousness.  It is used as a part of different religious traditions but can also be used as a secular practice.  Meditation typically consists of the repetition of a mantra – a sound, word, or phrase. In other forms of mediation, the focus is on a picture, flame, or specific part of the body.  Regardless of the point of focus, the key to the procedure is concentrating to the point where the meditator becomes unaware of any outside stimulation and reaches a different state of consciousness. Meditation  After meditation, people report feeling relaxed. They sometimes relate that they have gained new insights into themselves and the problems they are facing.  The long-term practice of meditation also improves the health of both brain and body because of the biological changes it produces.  Oxygen increases  Heart rate and blood pressure decline  Brain wave patterns may change  Sometimes meditation is combined with another technique, for example sweat lodges. This has been used by Indigenous cultures for its varied physical, psychological and spiritual benefits by combining intense heat to the meditative practice.