Sleep

Question 1

What are the behavioural criteria for sleep?

Answer 1

Stereotypic or species-specific posture

Minimal movement

Reduced responsiveness to external stimuli

Reversible with stimulation- unlike coma, anaesthesia or death

Question 2

How can sleep be physiologically measured?

Answer 2

Electroencephalogram (EEG)

Electrooculogram (EOG)

Electromyogram (EMG)

Question 3

Describe the EEG, EOG and EMG in stages 1 and 2 (NREM) of sleep.

Answer 3

Less muscle activity

Change in EEG- slowing

Eye movements suppressed

Question 4

Describe the EEG, EOG and EMG in stages 3 and 4 (NREM) sleep.

Answer 4

Don’t see rapid eye movements, more than in stages 1 and 2 though

More dramatic change in EEG, slower, dramatic waveforms

More suppression of muscle activity

Question 5

Describe the EEG, EOG and EMG in stage 5 (REM) sleep.

Answer 5

Rapid eye movements- big changes in EOG, big waveforms

EMG even more suppressed- preventing movement in sleep

Question 6

How long do sleep cycles last, and how many would you expect to have in a good night’s sleep?

Answer 6

90 minutes.

4-6 cycles.

Question 7

How is sleep controlled?

Answer 7

Reticular activating system- ‘gateway’ to consciousness.

When RAS is active, awake- sleep is suppressed.

Starts in brainstem and projects upwards, through lateral hypothalamus (promotes wakefulness), contains orexin/hypocretin system, and ventrolateral preoptic nucleus (anterior hypothalamus) promotes sleep.

Question 8

What is the role of the suprachiasmatic nucleus in sleep?

Answer 8

Synchronises sleep with falling light level- circadian synchronisation of sleep/wake cycle.

Question 9

Is sleep necessary?

Answer 9

Most/all animals sleep

Sleep deprivation is detrimental

Sleep is regulated accurately

Question 10

What are the psychiatric and neurological effects of sleep deprivation?

Answer 10

Sleepiness

Irritability

Stress

Mood fluctuations

Depression

Impulsivity

Hallucinations

Question 11

What are the neurological effects of sleep deprivation?

Answer 11

Impaired attention, memory, executive function

Risk of errors and accidents

Neurodegeneration (?)

Question 12

What are the somatic effects of sleep deprivation?

Answer 12

Glucose intolerance

Reduced leptin/ increased appetite

Impaired immunity

Increased risk of cardiovascular disease and cancer

Death

Question 13

What are the functions of sleep?

Answer 13

Restoration and recovery- but active individuals do not sleep more

Energy conservation- 10% drop in BMR, but lying still is just as effective

Predator avoidance- but why is sleep so complex?

Specific brain functions- memory, consolidation…

Question 14

After sleep loss, how is sleep regulated?

Answer 14

Reduced latency to sleep onset

Increase of slow wave sleep (NREM)

Increase of REM sleep (after selective REM sleep deprivation)

Question 15

When do dreams occur and what part of the brain is responsible?

Answer 15

Can occur in REM and NREM sleep

Most frequent in REM sleep

More easily recalled in REM sleep

Contents of dreams are more emotional than ‘real life’

Brain activity in limbic system higher than in frontal lobe during dreams

Question 16

What are the functions of dreams?

Answer 16

Safety valve for antisocial emotions

Disposal of unwanted memories

Memory consolidation

Question 17

What are the causes of chronic insomnia?

Answer 17

Physiological, e.g. sleep apnoea, chronic pain

Brain dysfunction, e.g. depression, fatal familial insomnia, night working

Question 18

How is insomnia treated?

Answer 18

Most hypnotics enhance GABAergic circuits

Question 19

What is narcolepsy?

Answer 19

Falling asleep repeatedly during the day and disturbed sleep during the night

Cataplexy (sudden, brief loss of voluntary muscle tone, often triggered by strong emotions, e.g. laughter)

Dysfunction of control of REM sleep

Orexin/hypocretin deficiency

Question 20

What are the effects of shift work on sleep?

Answer 20

Night working causes physiological processes to become desynchronised

This can lead to sleep disorders, fatigue, and an increased risk for some conditions such as obesity, diabetes, and cancer

Question 21

What are the recommendations for improving sleep quality through sleep hygiene?

Answer 21

Establishing fixed times for going to bed/waking up

Creating a relaxing bedtime routine

Only going to bed when you feel tired

Maintaining a comfortable sleeping environment

Not napping during the day

Avoiding caffeine, nicotine and alcohol late at night

Avoiding eating a heavy meal late at night

Don’t use back-lit devices shortly before going to bed