Sleep Flashcards
What are the 6 fundamental behavioral states associated with sleep?
Quiescence, posture, environment retrieval, elevated sensory arousal threshold, reversible, homeostatically regulated
What two observations define sleep?
Distinct behavior and electrophysiological stages
What do the leading theories point to for the function behind why we sleep?
Supports the CNS via maintenance/recovery (removal of waste) and computational power (regulating strength of synaptic connections)
What are the two clues that show there is a function behind sleep?
Universality of sleep across species, sleep deprivation has detrimental effects
What physiological processes occur during sleep?
Pulsatile release of hormones
Restorative functions
Metabolic clearance of waste
Memory consolidation
Brain development and plasticity
How does core temperature change during sleep?
It decreases by around one degree celsius
How does metabolic rate change during sleep?
Decreases by 5-10%
In which broad stage of sleep does growth hormone secretion increase?
NREM sleep
How does the rate of CSF flow change during sleep?
It increases - glymphatic system
What consequences does sleep deprivation have on the body?
Delirium
Mood changes
Lack of concentration
Loss of memory
Confusion
Paranoia
Hallucinations
ROS build up in gut
It is fatal - increases risk of illness and death
What did the Stanford sleep deprivation experiment involving Randy Gardner reveal about the brain’s protective measures during sleep deprivation?
The brain takes ‘micronaps’ of a few seconds long. Whilst the person is still awake, parts of the brain sleep
Sleep deprivation in middle-aged populations can lead to an increased risk of developing what disorder?
Alzheimer’s disease (Sabia et al, 2021)
What is meant by the term sleep pressure?
Need and desire to sleep increases as our time awake increases
Following sleep deprivation, what differences do the first and subsequent nights show in regards to sleep patterns?
First night: longer slow wave NREM sleep
Subsequent nights: longer REM sleep
Which metabolite is believed to cause sleep pressure via accumulation during waking hours?
Adenosine
How does adenosine impact sleep pressure?
Increases in concentration during waking hours and increases need to sleep
How does caffeine promote wakefulness?
Blocks adenosine receptors presynaptically, reduces sleep pressure and increases wakefulness
Adenosine reduces the release of which three other neurotransmitters?
Acetylcholine
Noradrenaline
Serotonin
When do adenosine concentrations naturally fall?
During sleep
Which areas of the brain are involved in forming patterns of sleep/wakefulness?
Suprachiasmatic nucleus in the hypothalamus
Retino-hypothalamic tract
How does the suprachiasmatic nucleus in the hypothalamus help to regulate circadian rhythms?
Helps to form sleep/wakefulness patterns
How does light influence sleep patterns?
Depolarizes specialized melanopsin retinal ganglion cells which reduces melatonin secretions and reduces sleepiness
What is the pathway of how retinal ganglion cells induce melatonin secretion?
Retinal ganglion cells > suprachiasmatic nucleus (hypothalamus) > paraventricular nucleus (hypothalamus) > superior cervical ganglion > pineal gland > melatonin
Retinal ganglion cells activate the suprachiasmatic nucleus which projects to the paraventricular nucleus of the hypothalamus. This relays a message to the superior cervical ganglion which projects to the pineal gland and induces melatonin secretion
What is the relationship between light intensity and melatonin secretions?
As light decreases, melatonin secretions increase
How does the hypothalamus contribute to the neural control of sleep?
Suprachiasmatic nucleus regulates circadian rhythms
How does the brain stem contribute to the neural control of sleep?
Reticular activating system is involved in arousal and wakefulness
What is the reticular activation system?
Network of neurons in brain stem involved in arousal and wakefulness
What type of neurons innervate the reticular activation system?
Cholinergic neurons
How does the thalamus contribute to the neural control of sleep?
Thalamocortical pathways generate spindles during NREM sleep - hallmark sign of stage 2 NREM
Sleep requires interaction between which 4 structures in the brain?
Thalamus
Hypothalamus
Cortex
Brain stem
What are sleep spindles?
Oscillation pattern generated by thalamic reticular nucleus (and other thalamic nuclei) during stage 2 NREM sleep
What are K complexes and what induces them?
EEG pattern of sudden high amplitude sharp wave that can either be induced by sudden external sensory stimuli (a loud noise for example) or can be generated spontaneously
During which stage of sleep are K complexes and spindles observed on EEG?
Stage 2 NREM
What waves are viewed on EEG during an awake period?
Alpha waves of 8-12Hz