2-14 Stages Of Sleep And Brain Mechanisms

Front 1

Objective

Describe the characteristics of the different stages of sleep.

Back 1

See study guide.

Front 2

Objective

Explain why REM sleep is called paradoxical sleep.

Back 2

REM sleep is called paradoxical sleep because it resembles deep sleep in some ways and light sleep in others. During REM sleep, there are bursts of rapid eye movements and the EEG shows irregular, low-voltage fast waves that indicate increased neuronal activity; in this regard, REM sleep is light. However, the postural muscles of the body, such as those that support the head, are more relaxed during REM than in other stage; in this regard, REM is deep sleep. REM is also associated with erections in males and vaginal moistening in females. Heart rate, blood pressure, and breathing rate are more variable in REM than in Stages 2-4. In short, REM sleep combines deep sleep, light sleep, and features that are difficult to classify as deep or light.

Front 3

Objective

Distinguish between REM and NREM sleep and dreams.

Back 3

REM sleep is characterized by periods of rapid eye movements. The stages other than REM are known as non-REM (NREM) sleep. Anyone who falls asleep first enters Stage 1 and then slow progresses through Stages 2, 3, and 4 in order, although loud noises or other intrusions can interrupt this sequence. After about an hour of sleep, the person begins to cycle back from Stage 4 through Stages 3, 2, and then REM. The sequence repeats, with each complete cycle lasting about 90 minutes.
Initially after the discovery of REM, researchers believed it was almost synonymous with dreaming. Researchers found that people who were awakened during REM sleep reported dreams 80% to 90% of the time. Later researchers, however, found that people also sometimes reported dreams when they were awakened from NREM sleep. REM dreams are more likely than NREM dreams to include striking visual imagery and complicated plots, but not always. Some people with brain damage continue to have REM sleep but do not report any dreams, and other people continue to report dreams despite no evidence of REM sleep. In short, REM and dreams usually overlap, but they are not the same thing.

Front 4

Objective

Describe the role of the reticular formation, locus coeruleus, and basal forebrain in arousal.

Back 4

See study guide.

Front 5

Objective

Explain how caffeine increases arousal.

Back 5

Caffeine, a drug found in coffee, tea, and many soft drinks, increases arousal (thus inhibiting sleep) by blocking adenosine receptors. Adenosine is an inhibitory neurotransmitter, believed to play a role in promoting sleep and suppressing arousal. Caffeine also constricts the blood vessels in the brain, thereby decreasing its blood supply.

Front 6

Objective

Identify the parts of the brain that are activated in REM sleep.

Back 6

During REM sleep, activity increases in the pons and the limbic system (which is important for emotional responses), as well as parts of the parietal and temporal cortex.

Front 7

Objective

Describe the role of the pons in REM sleep.

Back 7

Activity in the pons triggers the onset of REM sleep. REM sleep is associated with a distinctive pattern of high-amplitude electrical potentials known as PGO waves, for pons-geniculate-occipital. Waves of neural activity are detected first in the pons, shortly afterward in the lateral geniculate nucleus of the thalamus, and then in the occipital cortex. Besides originating the PGO waves, cells in the pons contribute to REM sleep by sending messages to the spinal cord, inhibiting the motor neurons that control the body’s large muscles. Thus, the messages from the pons to the spinal cord prevent action during REM sleep.

Front 8

Objective

Discuss common sleep disorders.

Back 8

See study guide.

Front 9

Objective

List the four symptoms of narcolepsy.

Back 9

1. Gradual or sudden attacks of sleepiness during the day.

2. Occasional Cataplexy: An attack of muscle weakness while the person remains awake. Cataplexy is often triggered by strong emotions, such as anger or great excitement.

3. Sleep Paralysis: An inability to move while falling asleep or waking up. Other people may experience sleep paralysis occasionally, but people with narcolepsy experience it more frequently.

4. Hypnagogic Hallucinations: Dreamlike experiences that the person has trouble distinguishing from reality, often occurring at the onset of sleep.

Front 10

polysomnograph

Back 10

A combination of EEG and eye-movement records

Front 11

alpha wave

Back 11

Waves at a frequency of 8 to 12 per seconds; characteristic of relaxation

Front 12

sleep spindle

Back 12

Consists of 12 to 14 Hz waves during a burst that lasts at least ½ a second

Front 13

k-complex

Back 13

Sharp high-amplitude waves associated with Stage 2 sleep

Front 14

slow-wave sleep

Back 14

Stages 3 and 4

Front 15

paradoxical sleep

Back 15

Deep sleep in some ways and light in others (see REM sleep)

Front 16

rapid eye movement (REM) sleep

Back 16

Periods of rapid eye movements during sleep; characterized by irregular, low-voltage fast waves that indicate increased neuronal activity, muscle relaxation, sexual responses, variable heart rate, blood pressure and breathing rate, and dreaming

Front 17

non-REM sleep

Back 17

Stages other than REM

Front 18

reticular formation

Back 18

A structure that extends from the medulla into the forebrain; essential for cortical arousal

Front 19

locus coeruleus

Back 19

Small structure in the pons that emits bursts of impulses in response to meaningful events; axons release norepinephrine throughout the cortex and increase wakefulness

Front 20

basal forebrain

Back 20

An area just anterior and dorsal to the hypothalamus; some of its axons release acetylcholine (which increases arousal); others axons release GABA, the brain’s main inhibitory neurotransmitter, which is essential for sleep

Front 21

adenosine

Back 21

An inhibitory neurotransmitter, believed to play a role in promoting sleep and suppressing arousal

Front 22

caffeine

Back 22

A drug found in coffee, tea, and many soft drinks, increases arousal (thus inhibiting sleep) by blocking adenosine receptors

Front 23

PGO wave

Back 23

Distinctive pattern of high-amplitude electrical potentials; precede the onset of REM sleep

Front 24

insomnia

Back 24

Inadequate sleep (whether someone feels rested the following day)

Front 25

sleep apnea

Back 25

The inability to breathe while sleeping

Front 26

narcolepsy

Back 26

A condition characterized by frequent periods of sleepiness during the day

Front 27

cataplexy

Back 27

An attack of muscle weakness while the person remains awake; triggered by strong emotions

Front 28

periodic limb movement disorder

Back 28

Repeated involuntary movement of the legs and sometimes arms

Front 29

REM behavior disorder

Back 29

A disorder in which people move around vigorously during their REM periods, apparently acting out their dreams

Front 30

night terrors

Back 30

Experiences of intense anxiety from which a person awakens screaming in terror