Sleep (L5) Flashcards
What is meant by…
- Circannual
- Circadian
Circannual - about a year
Circadian - about a day
Rhythms
- Endogenously generated but can be modulated by external cues (zeitgebers)
- Patterns of brain activity, hormone production and cell regeneration
Human biological clock
- Discovered by Carl Richter
1. Waking signals: Neurons in the upper pons produce Ach which activates the thalamus then the cerebral cortex
2. Brain tires: As ATP breaks down, adenosine builds up and triggers neuron activity in the ventrolateral preoptic nucleus
3. Suprachiasmatic nucleus acts as the brain’s clock
4. VLPO neurons release GABA and galanin which inhibit the ascending arousal system in the hypothalamus and pons
Suprachiasmatic nucleus (SCN)
- Part of the hypothalamus
- Main control centre of circadian rhythms
- Controlled by signals from the retina in the day and by melatonin from the pineal gland at night
Stages of sleep
- Measured using polysomnography (EEG and eye tracking)
- 3 stages of non-REM and 1 stage of REM
- 90 min cycle
- Human sleep cycle is 25.1 hours
NREM stage 1
- Light sleep
- Theta waves
- Fleeting thoughts
- Eyes move slowly
- Reduced muscle activity
Awake
- Beta waves
- Alpha waves when drowsy
NREM stage 2
- Light sleep
- Theta waves
- Sleep spindles (0.5s bursts of 10-16Hz waves)
- K-complexes (sharp negative then smaller positive wave)
NREM stage 3
- Deep sleep
- Delta waves
- Heart, breathing rate and temp decrease
- Reduced brain activity and muscle tone
REM sleep
- Rapid eye movement
- Heart rate and blood pressure increases
- Proportion increases during the night
- Paradoxical sleep
- Partial muscle paralysis
What 3 vital bodily functions does sleep deprivation affect?
- Thermoregulation
- Immune system
- Metabolism
- Associated with decreased attention and working memory
Insomnia
- Inadequate sleep caused by noise, stress, pain, diet, medication, etc.
- May be due to shifts in circadian rhythms
Sleep apnea
- Inability to breathe during sleep
- Symptoms include sleepiness during the day, impaired attention and depression
- Therapies involve weight loss, drugs or sleep
Narcoplepsy
- Frequent unexpected periods of sleepiness during the day
- REM sleep intruding into wakefulness
- Caused by lack of the hypothalamic cells that produce and release orexin
- Treated with stimulant drugs such as Ritalin
Periodic limb movement disorder
Repeated involuntary limb movements that can cause insomnia
REM behaviour disorder
Movement during REM period apparently acting out their dreams
Night terrors
An abrupt, anxious awakening from NREM sleep
Sleepwalking
Usually occurs during stages 3/4
What are the functions of sleep?
- Energy conservation (eg. animals increase sleep during hibernation)
- Memory consolidation
What is the effect of depriving people of…
- NREM sleep
- REM sleep
NREM sleep: impaired verbal learning, fatigue, hypersensitivity to muscle and bone pain
REM sleep: memory problems, excessive aggression
Consiousness
- Sleep is a state of unconsciousness
- Dreams are an altered state of consciousness
- Pre-sleep consciousness is called the hypnagogic state
- Post-sleep consciousness is called the hypnopompic state
Sleeping pills
- Usually benzodiazepines
- People become dependent and tolerant
- Reduce the proportion of time spent in REM sleep
Sleep paralysis
- Experience of waking up unable to move
Dream theories
- Freud proposed that dreams represent unacceptable wishes (supressed thought)
- Hobson + McCarley suggested that dreams are produced when the mind attempts to make sense of random neural activity during sleep
What occurs in the brain during dreaming?
- Amygdala is activated (associated with emotion)
- Visual association cortex is activated
- Motor cortex is activated (spinal neurons inhibit this expression)
- Prefrontal cortex is deactivated (lack of planning)
Lucid dreaming
The awareness of dreaming during the dream
