Sleep

Question 1

Disorders of Sleep

Answer 1

• Insomnia
• Sleep Apnea
• Narcolepsy
• REM sleep behaviour disorder
• Slow-wave sleep problems
• Fatal familial insomnia

Question 2

Characteristics of REM sleep

Answer 2

• Electroencephalography desynchrony (rapid, irregular waves)
• Lack of muscle tonus
• Rapid eye movements
• Penile erection or vaginal secretion
• Dreams

Question 3

Characteristics of Slow-Wave sleep

Answer 3

• Electroencephalography synchrony (slow waves)
• Moderate muscle tonus
• Slow or absent eye movements
• Lack of genital activity

Question 4

Functions of slow-wave sleep

Answer 4

• Slow-wave sleep deprivation affects cognitive abilities, especially sustained attention, but not physical abilities
• Cerebral metabolic rate and blood flow falls by about 75%.
• This coupled with people’s unresponsiveness, and confusion if awakened suggests cerebral cortex ‘shuts down’ during sleep.

Question 5

Functions of REM sleep.

Answer 5

• If deprived of REM sleep, you will have more REM sleep in the next sleep period (Rebound phenomenon).
• Highest proportion of REM sleep occurs during brain development

Question 6

Findings of studies of the effect of sleep on learning

Answer 6

• REM sleep facilitates consolidation of nondeclarative memories
• Slow-wave sleep facilitates consolidation of declarative memories

Question 7

Neurotransmitters that play a role in arousal.

Answer 7

Acetylcholine
Norepinephrine
Serotonin
Histamine
Orexin

Question 8

Describe the neural control of slow-wave sleep.

Answer 8

• controlled by 3 factors – homeostatic, allostatic, and circadian.
• Primary homeostatic factor – presence or absence of adenosine.
• Allostatic control is mediated by hormonal and neural responses to stressful situations

Question 9

So if a high level of activity in the arousal related neurons keeps us awake and a low level puts us to sleep, what controls the activity of these neurons?

Answer 9

• Inhibition of the arousal system is necessary for sleep
• Group of GABAnergic neurons in the ventrolateral preoptic area (vlPOA) become active and supress activity of arousal neurons.

Question 10

What is the sleep/wake flip-flop

Answer 10

• The flip-flop is on when the sleep-promoting neurons in the vlPOA are inhibited and the arousal neurons are active
• The flip-flop is off when the sleep-promoting neurons in the vlPOA are activated and the arousal neurons are inhibited

Question 11

Describe the effect of the orexinergic neurones in the sleep/wake flip-flop

Answer 11

• Orexinergic neurons help to stabilise the sleep/waking flip/flop
• Motivation to remain awake or events that disturb sleep activate the orexinergic neurons.

Question 12

What factors control the activity of the orexinergic neurons?

Answer 12

• Biological clock
• Hunger related signals activate them
• Satiety related signals inhibit them
• Orexinergic neurons receiving inhibitory input from the vlPOA because of a build-up of adenosine.

Question 13

Describe the Neural Control of REM Sleep

Answer 13

• Acetylcholinergic neurons also fire at a high rate in REM sleep
• There is a REM flip-flop
• REM-ON neurons are located in the pons
  REM-OFF neurons are located in the midbrain

Question 14

Causes of insomnia

Answer 14

• Age - More common in older people
• Environmental factors
  ○ Electronic devices, noise, light–detrimental
  ○ White noise or other repetitive noise - beneficial
• Physiology
  ○ Heightened activity in the reticular activating system
• Circadian rhythms
• Medical conditions and medications

Question 15

Treatment of insomnia

Answer 15

• drugs, mindfulness and CBT.

Question 16

What is sleep apnea

Answer 16

• Form of insomnia – the inability to sleep and breathe at the same time
• Build of carbon dioxide in the blood stimulates chemoreceptors
• Disrupts sleep affecting daytime functioning
• If caused by obstruction can be corrected surgically or relieved by pressurised air that keeps the airway open

Question 17

Narcolepsy symptoms

Answer 17

• Sleep attack – overwhelming urge to sleep
• Cataplexy – muscular paralysis of REM sleep while awake
  ○ Varying degrees of muscle weakness
  ○ Can become completely paralyzed while conscious
  ○ Generally occurs when the person feels strong emotions or by sudden physical effort.
• Sleep paralysis
  ○ REM muscular paralysis just before the onset of sleep or upon waking
• Hypnagogic hallucinations
  ○ dreaming while awake and paralysed
  ○ can very realistic and terrifying.

Question 18

Causes of Narcolepsy

Answer 18

• Hereditary element
• Environmental factors play a role but are unknown
• Orexinergic neurons are attacked by the immune system, usually in adolescence

Question 19

Treatments of Narcolepsy

Answer 19

• Sleep attacks diminished with stimulants e.g methylphenidate (Ritalin)
• REM sleep phenomenon (cataplexy, sleep paralysis and hypagogic hallucinations) treated with antidepressant drugs
• Most common current treatments are modafanil and/or sodium oxybate (GHB; gamma hydroxybutyric acid), both stimulant drugs

Question 20

What is REM Sleep Behaviour Disorder

Answer 20

• Neurodegenerative disorder with a genetic component
• Failure to exhibit paralysis during REM sleep
• Acting out dreams

Question 21

Name some slow-wave sleep problems

Answer 21

• Sleepwalking (Somnambulism)
• Night terrors (pavor nocturnus)
• Bedwetting (nocturnalenuresis)

Question 22

What is Fatal Familial Insomnia

Answer 22

• Neurodegenerative condition
  
  • Prion disease - caused by build up of abnormal prion proteins which are resistant to being broken down by enzymes = accumulation = damage to brain
  • Damage to the thalamus
  • Initially presents with insomnia and very vivid dreams when the person finally manages to sleep.
  • Psychiatric complications – panic attacks, cognitive deficits, paranoia and phobias
  • As the disease progresses it affects the autonomic nervous system (e.g. elevated blood pressure) and coordination (ataxia)
  • EEG shows disturbances and reductions in sleep spindles and K complexes
  • Disappearance of slow-wave sleep and only brief periods of REM sleep
  • Ultimately inability to voluntarily move or speak (akinetic mutism), coma, and death.