What four characteristics help to define sleep?
The four characteristics that help to define sleep are:
- Diminished motor ability
- Reduced responses to external stimuli
- Generalized posture
- Readily reversible state
These characteristics distinguish sleep from both coma and hibernation.
An EEG (electroencephalogram) is a test that measures and records the electrical activity of the brain.
During an EEG electrodes are attached to the scalp and a computer records lines that correspond to the brain's electrical waves.
EEGs are commonly used in sleep studies and for many other brain-related diagnostic tests.
List the four types of EEG waves in order of decreasing frequency.
In order of decreasing frequency, the four types of EEG waves are:
- Beta waves (13-60 Hz)
- Alpha waves (8-12 Hz)
- Theta waves (3-8 Hz)
- Delta waves (0.5-3 Hz)
At the same time, as frequency of the waves decreases, amplitude increases.
Non-REM sleep first occurs right after falling asleep and is characterized by a progressive decrease in brain activity; the person gradually falls into a deeper sleep.
Non-REM is comprised of four stages of varying brain waves; all of which are considered slow, high altitude oscillations.
Which component of the body's nervous system is activated during non-REM sleep?
During non-REM sleep, the parasympathetic nervous system is most predominant.
During this time, general metabolism slows, leading to a decrease in body temperature, heart rate, respiratory rate, energy consumption, and kidney function.
stage 1 of non-REM sleep
Stage 1 of non-REM sleep is the very start of the sleep cycle, when the sleeper first lies down, closes his eyes, and begins to relax.
Stage 1 begins with rapid beta waves, moves towards slower alpha waves, and ends with the emergence of theta waves.
Waking a person from sleep is easiest during stage 1, despite a markedly diminished reaction to stimuli.
How long does stage 1 of non-REM sleep typically last?
Stage 1 lasts between 3 and 12 minutes.
Stage 1 accounts for only 5% of a young adult's total sleep cycle.
stage 2 of non-REM sleep
Stage 2 of non-REM sleep is the stage of light sleep marked by an even greater decline in external stimuli response.
The theta waves associated with stage 2 continue to decrease in speed and are often interrupted with high frequency waves, called sleep spindles, and high altitude waves, called K-complexes.
How long does stage 2 of non-REM sleep typically last?
Stage 2 lasts between 10 and 20 minutes.
Stage 2 accounts for more than 50% of a young adult's total sleep cycle.
stage 3 of non-REM sleep
Stage 3 of non-REM sleep marks the passage into deep sleep in which the sleeper shows very little response to external stimuli.
During stage 3, the slow delta waves appear on EEG, while the presence of sleep spindles and K-complexes diminish.
How long does stage 3 of non-REM sleep typically last?
Stage 3 lasts approximately 10 minutes in the first sleep cycle, but decreases in subsequent cycles.
Stage 3 accounts for approximately 7% of a young adult's total sleep cycle.
stage 4 of non-REM sleep
Stage 4 of REM sleep is the deepest stage of sleep, in which neuronal activity is at its highest. Stage 4 experiences the highest respiratory rate, breathing rate, heart rate, and blood pressure.
Delta waves dominate the EEG in this stage of sleep.
How long does stage 4 of non-REM sleep typically last?
Stage 4 lasts approximately 35-40 minutes during the first sleep cycle.
Stage 4 accounts for 15-20% of a young adult's total sleep cycle.
REM is characterized by high energy brainwaves, similar to those found in the wake cycle, and rapid eye movement, from which REM sleep gets its name.
The first cycle of REM sleep occurs after the first complete cycle of non-REM sleep.
What are five characteristics of REM sleep?
Five characteristics of REM sleep are:
- Low amplitude, high frequency wave lengths
- Vivid, internally produced sensations
- Motor activity of extremities is non-existent
- Frequent and rapid movement of the eyes (REM)
- Repetitive and illogical thoughts
How long does REM sleep typically last?
REM sleep lasts about 10-15 minutes.
REM sleep comprises approximately 20-25% of an adult's sleep cycle.
On average, how many hours does an adult sleep per night?
Adults get an average of 7-8 hours of sleep per night.
The amount of sleep people receive is influenced by genetic make-up, lifestyle, and age.
Typically, as humans age, sleep becomes more frequent and fragmented.
the basic order of stages of the sleep cycle
The sleep cycle begins with stage 1 of non-REM and progresses through stages 2-4 before REM sleep is reached. After REM, sleep progresses back through non-REM beginning with stage 4 and ending with stage 1. The cycle continues to repeat throughout the night.
How long does each sleep cycle last?
Depending on the individual, each sleep cycle lasts anywhere from 1.5 to 2 hours.
How many complete sleep cycles are typical of a full night's sleep?
In a full night's sleep, the sleep cycle is typically completed 4 to 6 times.
What stage of sleep consumes the largest proportion of the sleep cycle?
Stage 2 of non-REM consumes the largest proportion of the sleep cycle at 50-60%.
During which stage of the sleep cycle does dreaming occur?
Dreaming can occur during both REM and non-REM sleep.
Non-REM dreams are often short, with concrete and logical structure. On the other hand, REM sleep dreams are vivid, emotional, and often illogical.
the psychoanalytic theory, as it relates to dreams
The psychoanalytic theory of dreams holds that dreams are a window into the unconscious, whereby repressed desires, feelings, and emotions are revealed.
The psychologist Sigmund Freud is considered to be the father of the psychoanalytic theory.
the activation-synthesis model, as it relates to dreams
The activation-synthesis model holds that dreams are the result of the sleeping brain's attempt to assign meaning to and extract coherent images from the random nerve impulses sent through the sleeping brain.
the active unlearning theory, as it relates to dreams
The active unlearning theory holds that dreams are the result of the brain examining the stimuli it has received throughout the day and discarding the information that has no meaning.
The active unlearning theory may explain why dreams are so difficult to remember, as it is information we are supposed to forget anyway.
What are some symptoms of sleep deprivation syndrome?
Some symptoms of sleep deprivation syndrome include:
- Decreased alertness and ability to think and concentrate
- Slowed reflexes
- Issues with remembering
- Muscle fatigue
- Mood swings
Insomnia is the inability to get the quantity or quality of sleep needed to avoid the symptoms of sleep deprivation and to function on a daily basis.
There are two types of insomnia; transitory insomnia and chronic insomnia.
Transitory insomnia is a type of insomnia that is short-term, lasting at most a few weeks, and typically results from high levels of stress or caffeine, or even jet lag.
Chronic insomnia is a long-lasting form of insomnia that typically lasts for longer than a month and can be caused by a multitude of external or internal issues.
External issues include factors such as excessive heat, cold, or noise.
Internal issues include factors such as chronic pain, coughing, or difficulty breathing, as well as psychological illnesses such as depression.
Sleep apnea is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing rate.