Sleep

Question 1

What is the behavioural criteria for sleep

Answer 1

Altered consciousness
Decreased sensory and motor activity
Decreased ability to respond to environmental stimuli
Reversible with stimulation – unlike coma, anaesthesia or death

Question 2

What are the stages of sleep

Answer 2

1. Awake
2. Stage 1 + 2 NREM
3. Stage 3 + 4 NREM
4. Stage 5 REM

Question 3

What is the psychological criteria for sleep

Answer 3

Brain activity - electroencephalogram
Eye movements - electrooculogram
Muscle - Electromyogram

Question 4

Describe the sleep cycle

Answer 4

Transitioning from wakefulness into NREM sleep (4 stages)
Usually lasts 90 minutes
Good night’s sleep will usually consist of 4-6 complete sleep cycles
Amount of time spent in deep sleep is highest earlier in the night, and reduces with each sleep cycle and reduces with each sleep cycle.
The period of REM sleep gets progressively longer with each sleep cycle

Question 5

Describe the EEG, EOG and EMG recordings when awake

Answer 5

EEG – fast brain rhythm – beta waves (~30 Hz)

EMG – reasonable amount of muscle tone because you are maintaining posture and ready for action

Question 6

Describe the structure of sleep

Answer 6

around 5 cycles of the stages with 5 REM stages

Question 7

Describe the maintenance of arousal

Answer 7

Reticular activating system controls consciousness.
Begins in the brainstem and projects upwards
Lateral hypothalamus promotes wakefulness (orexin/hypocretin)
Ventrolateral pre-optic nucleus/anterior hypothalamus promotes sleep

Question 8

what are the psychiatric and neurological effects of sleep deprivation

Answer 8

Sleepiness
Irritability 
Stress
Mood fluctuations
Depression
Hallucinations

Question 9

What are the neurological effects of sleep deprivation

Answer 9

Impaired attention, memory, executive function
Risk of errors and accidents
Neurodegenerations

Question 10

What are the somatic effects of sleep deprivation

Answer 10

Glucose intolerance
Reduced leptin/increased appetite 
Impaired immunity 
Increased risk of cardiovascular disease and cancer
Death

Question 11

Describe three ways in which sleep is regulated after sleep deprivation.

Answer 11

Reduced latency to sleep onset
Increase of slow wave sleep (NREM)
Increase of REM sleep (after selective REM sleep deprivation)

Question 12

What are the functions of sleep

Answer 12

Restoration and recovery (but active individuals do not sleep more)
Energy conservation – 10% drop in BMR (lying still is just as effective)
Specific brain functions – memory consolidation
(Predator avoidance)

Question 13

When do dreams occur during sleep

Answer 13

Can occur in REM and NREM, more frequent in REM

More easily recalled in REM

Question 14

What are the functions of dreams

Answer 14

Safety valve for antisocial emotions
Disposal of unwanted memories
Memory consolidation

Question 15

What are the causes of chronic insomnia

Answer 15

Physiological e.g. sleep apnoea, chronic pain

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

Question 16

What is the treatment for insomnia

Answer 16

Sleep hygiene
Hypnotics (most enhance GABAergic circuits)
Sleep CBT

Question 17

How can sleep hygiene be improved

Answer 17

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

Question 18

What are some causes of hypersomnia

Answer 18

Narcolepsy
Idiopathic hypersomnolence
Post-traumatic brain injury

Secondary causes (poor night sleep)
Obstructive sleep apnoea
Nocturnal pain e.g. diabetic neuropathy/arthritis
Anxiety
Medication
Restless legs syndrome and limb movements in sleep

Question 19

What diagnostic tool can be used to help for sleepiness

Answer 19

Epworth sleepiness scale

Question 20

Describe narcolepsy

Answer 20

Falling asleep repeatedly during the day and disturbed sleep during the night
Cataplexy (sudden, brief loss of voluntary muscle tone, triggered by storm emotions e.g. laughter)
Dysfunction of control of REM sleep
Orexin/hypocretin deficiency

Question 21

What is the effect of shift work on sleep

Answer 21

Night working causes physiological processes to be desynchronised
Leads to sleep disorders, fatigue and an increased risk for some conditions (obesity, diabetes and cancer)

Question 22

Describe the EEG, EOG and EMG recordings in stage 1 + 2 sleep

Answer 22

Light sleep
EEG – theta (4-8 Hz) waves – gradually becoming more and more drowsy
EOG – NO eye movements
EMG – muscle activity reduced considerably

Question 23

Describe the EEG, EOG and EMG recordings in stage 3 + 4 sleep

Answer 23

Very deep sleep
EEG - Delta activity (< 4 Hz)
EOG – minimal eye movement
EMG – continued relaxation of muscles

Question 24

Describe the EEG, EOG and EMG recordings in stage 5 sleep

Answer 24

EOG activity increases greatly

EEG is similar to that of awake

Question 25

Describe how heart rate and respiratory rate change during sleep

Answer 25

SLOW during NREM

FAST during REM sleep

Question 26

Describe the circadian synchronisation of the sleep-wake cycle.

Answer 26

The suprachiasmatic nucleus - synchronisation with falling light level
It receives an input from the retina (not from the usual photogenic cells) and as light level falls the suprachiasmatic nucleus becomes more active

Question 27

Describe the effect of the suprachiasmatic nucleus on the nuclei within the hypothalamus.

Answer 27

Falling light level –> increased activity of suprachiasmatic nucleus
This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier

Question 28

What other important projection does the suprachiasmatic nucleus have and what is the importance of this projection?

Answer 28

Projection to the pineal gland
Increase in suprachiasmatic nucleus activity leads to activation of pineal gland so that it releases melatonin
Melatonin adjusts various physiological processes in the body that fit with sleep