Sleep Flashcards
Why do we sleep?
Moruzzi - restoration. Clearance of toxic waste products.
Meddis - adaptation - prevent accidents and predation at night. Saves energy + allows awakening when needed.
What predicts diurnal preference?
Length of per3 gene.
Can change over our life.
Innate differences in circadian period.
What does sleep deprivation cause?
Gardner - awake for 264 hours. Tremor, language problems, EEG abnormality.
Drummer & Dinges - impacts mood, cognitive performance, motor function.
How is sleep measured?
Patient-report outcomes, actigraphy, PSG, actigraphy.
PSG - recording of multiple signals during sleep. EEG, EMG, EOG.
What has been linked to memory consolidation?
Light, non-REM sleep.
How is REM different to slow wave sleep?
REM: low amplitude, core temperature, drop, strong descending inhibition of motor neurones, raised arousal threshold, sudden eye movements, many dreams.
What are the three main mechanisms of sleep?
Reticular formation - modulatory systems control rhythmic behaviours of thalamus. Inhbiits descending pathways.
Cortisol - don’t sleep well = raised cortisol. Oscillates throughout the day but peaks just before waking up.
Melatonin - prepares you for darkness behaviour. Pineal gland. Biological clock drives melatonin rhythm. Can help diagnose circadian rhythm disorders. Affected by light.
What are the main neural mechanisms of sleep?
Noradrenaline, serotonin, aCh, histamine hypocretin - arousal promoting.
Synapse on thalamus + cerebral cortex - depolarisation of neurons - increase excitability.
What promotes sleep?
Adenosine - inhibits systems which promote wakefulness.
Gaba.
ACh neurons fire to induce REM.
Dopamine - modules REM sleep.
What happens when going to sleep?
Increase of GABAergic activity in cortex.
Less activity of reticular activating system.
Increase melatonin.
Reduced histamine.
Name the main sleeping disorders.
Insomnias - stress, environmental factors, medication.
Hypersomnolence - daytime sleeping.
Parasomnias - sleep walking, night terrors, REM sleep behaviour disorder (treatment = benzodiazepines/melatonin).
Circadian rhythm disorders - timing of sleep. Intrinsic. Co-morbid with ADHD, depression or neurodegenerative diseases. Treatment = light exposure/melatonin.
Breathing disorders - sleep apnea (blockage of airway - oxygen level drops). Weight, alcohol, smoking…
Narcolepsy - due to significantly less hypocretin than normal.
What is the dual process model of sleep?
Sleep-wake homeostasis - accumulation of hypogenic substances in brain.
Circadian rhythms - regulates body’s internal processes + alertness. Zeitbergs (external cues) - without them, rhythms run free. Cave study - awake for 20 hours, sleep for 12.
Where is our biological clock located?
Suprachiasmatic nuclei within hypothalamus.
Input from ganglion cells - large, non-selective receptive fields responding to luminance.
What are some consequences of jetlag?
Elevated cortisol, sleepless, change in appetite.
Why do we dream?
Wish fulfilment - Freud.
Physiological function theory - promotes neural development. Provides brain with stimulation.
Activation-synthesis model - Hobson & McCarley - dreams are products of brain neutron activity in visual cortex, memory + emotion areas. No external stimulus - brain tries to make sense of neuron activity. Explains randomness of dreams, PFC shuts down during REM - fewer inhibitions when dreaming.
