Chapter 3 - Sleep

Question 1

What is sleep?

Answer 1

Sleep can be described as a regularly occurring altered state of consciousness that typically occurs spontaneously and is primarily characterised by a loss of conscious awareness.

Question 2

What is polysomnography?

Answer 2

Polysomnography is an intensive study of a sleeping person involving simultaneous monitoring and recording of various physiological responses of the sleeper during the course of the night.

Question 3

What is the electromyograph?

Answer 3

The electromyograph is a device used to detect, amplify and record the electrical activity of muscles.

Question 4

What is the electro-oculogram?

Answer 4

The electro-oculogram is a device for measuring eye movements or eye positions by detecting, amplifying and recording electrical activity in eye muscles that control eye movements.

Question 5

What is a sleep diary?

Answer 5

A sleep diary is a self-reported record of an individual’s sleep and waking time activities, usually over a period of several weeks.

Question 6

When are sleep diaries most commonly used?

Answer 6

Sleep diaries are most commonly used in conjunction with polysomnographic tests to support the assessment of sleep disorders and problems, particularly their nature, severity and causes.

Question 7

How long does one cycle of NREM sleep typically last in adults?

Answer 7

70 - 90 minutes.

Question 8

What does a complete sleep cycle consist of?

Answer 8

A complete sleep cycle consists of a period of NREM sleep (but not necessarily all four NREM stages) and a period of REM sleep (which tends to increase in duration as the night progresses).

Question 9

How long does a complete sleep cycle last?

Answer 9

Generally for about 80 to 120 minutes.

Question 10

How many times do we go through this sleep cycle during a typical eight hours of sleep a night?

Answer 10

Four to five times.

Question 11

How much of our sleep time is spent in NREM sleep?

Answer 11

Approximately 80% of our sleep time is spent in NREM sleep, and typically the first half of the night has more NREM sleep than the second half of the night.

Question 12

What is the hypnogogic state?

Answer 12

The transition period from being awake to being asleep.

Question 13

What does NREM sleep consist of?

Answer 13

NREM sleep consists of four different stages in which the sleeper progresses from a stage of light sleep to the stage of deepest sleep and back again through one or more stages of light sleep.

Question 14

Describe our level of awareness throughout NREM stage 1 sleep.

Answer 14

We tend to gradually lose awareness of ourselves and our surroundings, but some of the time we are actually aware of faint sounds in our environment.

Question 15

Describe the brain wave patterns of NREM stage 1 sleep.

Answer 15

There is a decrease in alpha brain wave production as these brain waves are replaced by more irregular, medium-frequency theta waves, which have a mixture of high and low amplitude.

Question 16

Describe some of the physiological changes that occur during NREM stage 1 sleep.

Answer 16

There is a lower level of bodily arousal, indicated by a decrease in heart rate, respiration, body temperature, blood pressure and muscle tension.

Question 17

What is a hypnic jerk?

Answer 17

A hypnic jerk is a sensation whereby our body, or a part of our body, seems to go into a spasm. It is a common occurrence during NREM stage 1.

Question 18

How long does NREM stage 1 last for?

Answer 18

Five to ten minutes.

Question 19

Describe our level of awareness throughout NREM stage 2 sleep.

Answer 19

Although our sleep is less easily disturbed than it is in stage 1, we can still be easily aroused from this sleep stage. Although we are asleep, the brain still responds to various external or internal stimuli, such as the sound of a knock on the door, or muscle tension in our leg as we move. About midway through stage 2, we are unlikely to respond to anything except extremely strong or loud stimuli.

Question 20

Describe the brain wave patterns of NREM stage 2 sleep.

Answer 20

Brain waves are mainly theta waves, but are slightly lower in frequency and higher in amplitude than the theta waves produced in stage 1.

Question 21

What are sleep spindles and how long do they last?

Answer 21

Sleep spindles are brief bursts of higher frequency brain wave activity and last for about one second. Their presence is an indicator that a person is truly asleep.

Question 22

What is a K complex?

Answer 22

A K complex is a burst of low frequency and slightly higher amplitude waves, in response to arousing stimuli.

Question 23

Describe some of the physiological changes that occur during NREM stage 2 sleep.

Answer 23

Body movements lessen, breathing becomes more regular, blood pressure and temperature continue to fall, and heart rate is lower.

Question 24

How long does NREM stage 2 last for?

Answer 24

Ten to twenty minutes.

Question 25

Describe our level of awareness throughout NREM stage 3 sleep.

Answer 25

The individual is extremely relaxed and becomes less and less responsive to the outside world. In this stage, people are difficult to arouse, but if they are awoken they are often groggy and disoriented.

Question 26

Describe the brain wave patterns of NREM stage 3 sleep.

Answer 26

During stage 3, there is a reduction in the brain’s electrical activity, and delta waves begin to appear in the EEG recording. Delta waves make up about 20-50% of the brain waves recorded during stage 3, being slow, large, regular brain waves. They are lower in frequency and higher in amplitude than the alpha and theta waves of stages 1 and 2.

Question 27

Describe some of the physiological changes that occur during NREM stage 3 sleep.

Answer 27

Heart rate, blood pressure and body temperature continue to drop, and breathing rate continues to be slow and steady.

Question 28

How long does NREM stage 3 last for?

Answer 28

About ten minutes.

Question 29

When do we begin and how long do we remain in slow wave sleep?

Answer 29

Slow wave sleep is marked by the presence of delta waves and generally begins within an hour of falling asleep. We remain in slow wave sleep for about 30 minutes.

Question 30

When has someone entered stage 4 NREM sleep?

Answer 30

When the EEG recordings show that delta waves comprise more than 50% of the brain wave activity.

Question 31

Describe the muscle tone and activity during NREM stage 4 sleep.

Answer 31

Muscles are completely relaxed and we barely move.

Question 32

Describe the brain wave patterns of NREM stage 4 sleep.

Answer 32

Delta waves dominate the EEG pattern and are even slower and larger than those in stage 3.

Question 33

Describe our level of awareness throughout NREM stage 4 sleep.

Answer 33

A person in stage 4 is very difficult to wake. It is the point at which people are often said to be ‘sleeping like a log’ or ‘out like a light’.

Question 34

Describe sleep inertia.

Answer 34

When people are woken from NREM stage 4, they can take up to ten minutes to orient themselves, and usually have a poor memory of sleep events. This is sometimes referred to as ‘sleep drunkenness’, although psychologists prefer the term ‘sleep inertia’ when referring to the post awakening mental lag.

Question 35

How long do we spend in NREM stage 4?

Answer 35

In the first cycle of sleep, we may spend about 20 minutes in stage 4. However, as the night progresses, less and less time is spent in stages 3 and 4. In sleep cycles close to the morning, there may be no stage 3 or 4 sleep at all.

Question 36

What sleep phenomena occur in the very deep sleep of stages 3 and 4?

Answer 36

Sleepwaking, sleep talking, night terrors. Bedwetting may also occur (more so than in other stages).

Question 37

How long does the progression from stage 1 to stage 4 NREM take before we move back through stages 3 and 2?

Answer 37

45 to 60 minutes.

Question 38

Define REM sleep.

Answer 38

REM sleep is a period of rapid-eye-movement sleep during which the eyeballs rapidly move beneath the closed eyelids, darting back and forth and up and down in jerky movements.

Question 39

Describe the brain wave pattern of REM sleep.

Answer 39

The brain wave pattern associated with REM sleep is irregular, consisting of low amplitude, relatively high frequency beta-like waves.

Question 40

Describe the physiological characteristics of REM sleep.

Answer 40

The heart rate is faster and more irregular. Blood pressure rises, and breathing is quicker and more irregular. However the sleeper is totally relaxed. Although there are occasional twitching movements in the small muscles of the face, fingers and toes, most of the skeletal muscles are limp, and the body shows few outward signs of movement.

Question 41

Why is REM sleep called paradoxical sleep?

Answer 41

Internally, the brain and body are active, while, externally, the body appears calm and inactive.

Question 42

Contrast dreaming that occurs during REM and NREM sleep.

Answer 42

Most dreaming occurs during REM sleep. Dreaming also occurs during NREM sleep, but the dreams are less frequent, less memorable, less vivid and less fragmented than those of REM dreams.

Question 43

How long does REM last for?

Answer 43

A REM period occurring early in the night may only last a few minutes, while a later REM period may last up to an hour or so.

Question 44

Describe sleep patterns of various age groups and time spent in REM.

Answer 44

• Newborns - 16 hours sleep, 50% REM.
• Children - 12-13 hours sleep, 25-30% REM.
• Adolescents - 9 hours sleep, 20% REM
• Late adulthood - 6-7 hours sleep, one third REM.

Question 45

What is the circadian rhythm?

Answer 45

The circadian rhythm is our body’s daily cycle during which hormones are produced to control body functions, and the sleep hormone melatonin causes us to feel sleepy at night. The cycle is linked to external cues in the environment , such as the presence or absence of sunlight, alarm clocks, meal times and even television.

Question 46

What is the sleep-wake cycle shift?

Answer 46

During adolescence, there is a hormonally induced shift of the body clock forward by about one to two hours, making the adolescent sleepier one to two hours later. This is known as the sleep-wake cycle shift.

Question 47

What is sleep debt?

Answer 47

Nightly sleep loss can accumulate as a sleep debt; that is sleep that is lost and needs to be made up.

Question 48

What do restorative theories of sleep propose?

Answer 48

Generally, restorative theories propose that sleep provides ‘time out’ to help us recover from depleting activities during waking time that use up the body’s physical and mental resources.

Question 49

What do survival theories of sleep propose?

Answer 49

Survival theories of sleep propose that sleep evolved to enhance survival by protecting an organism through making it inactive during part of the day when it is most dangerous to move about.

Question 50

Define sleep deprivation, partial sleep deprivation and total sleep deprivation.

Answer 50

Sleep deprivation means going without sleep. Partial sleep deprivation involves having less than what is normally required. Total sleep deprivation involves not having any sleep at all.

Question 51

List some effects of partial sleep deprivation.

Answer 51

Tiredness, lapses in attention, inability to concentrate for a long period of time, a low level of motivation, impaired motor skills, irritability, impaired processing of information in short-term memory and occasional headaches.

Question 52

List some effects of total sleep deprivation.

Answer 52

Sleepiness, fatigue, hand tremors, drooping eyelids, difficulty focusing the eyes, lack of energy and strength, slurred speech and an increased sensitivity to pain.

Question 53

What is a microsleep?

Answer 53

A microsleep is a very short period of drowsiness or sleeping that occurs while the person is apparently awake. During a microsleep, the EEG pattern resembles that of the early stages of NREM sleep. After a microsleep, which usually lasts for a very brief period of time, individuals may have no recollection of what happened during the microsleep.

Question 54

What is REM rebound?

Answer 54

REM rebound involves catching up on REM sleep immediately following a period of lost REM sleep by spending more time than usual in REM sleep when next asleep.

Question 55

What is hypersomnia?

Answer 55

Difficulty waking up.

Question 56

What is insomnia and list characteristics of insomnia.

Answer 56

Difficulty falling asleep. Characteristics include:

• Failure to fall sleep
• Waking during the night
• Feeling tired during the day