Sleep Physiology Flashcards
What is the sleep?
Normal, recurring reversible state = loss of ability to respond to external environment, not fully aware of self and environment but can respond when stimulated
What are some features of non-REM sleep?
More non-REM sleep at start of the night, synchronised rhythmic EEG activity, partial muscle relaxation, reduced cerebral blood flow, reduced heart rate and BP, some non-narrative images
What are some features of REM sleep?
Mostly at end of night, EEG shows fast activity, fMRI shows increased brain activity, atonic muscles, cerebral blood flow increased, impaired thermal regulation, narrative dreaming
What are some features of deep sleep?
Essential sleep = only part of lost sleep regained after sleep loss, allows cortex to recover after busy day
Is REM classed as true sleep?
No = actually a form of non-wakefulness, mainly for early brain development, likely dispensable
What drug class suppress REM sleep with no effect?
Tricyclic antidepressants
How does sleep change throughout childhood?
Neonates = spend 16hrs per day asleep, 50% REM sleep, shorter cycles
During 1st decade percentage REM sleep falls and REM latency increases
What are some features of sleep in the elderly?
Increased awakenings
Reduced REM latency, total sleep time and daytime napping
What are the three critical processes involved in sleep onset?
Homeostatic response, emotional response and circadian rhythm = biology and physiology control sleep
What is circadian rhythm important for?
Sleep-wake cycle, appetite and hormone secretion
How does timing of sleep onset change with age?
Children sleep earlier and waken earlier, adolescents have delayed sleep pattern, elderly have an advanced sleep pattern
How long does circadian rhythm normally last for?
25 hours
What controls the body’s internal clock?
Light = uses retinal ganglion cells projecting to suprachiasmatic nucleus = non-rod, non-cone cells
How does sleep help exercise?
No evidence of muscle recovery during sleep but does help with tissue repair
Growth hormone release is sleep related
Cell division and skin mitosis peaks during sleep
When can the cortex rest?
Can only rest during sleep = can’t fully rest when awake as stays in quiet readiness
What effect does the number of function a cortex perform have on how much sleep it requires?
More complicated cortices require more sleep
What effect does lack of sleep have on the brain?
Most effects are prefrontal = no psychoses but become irritable and suspicious, visual illusions, microsleeps and concentration lapses also occur
What is the function of the prefrontal cortex?
Doesn’t effect old and well-rehearsed tasks
Routine behaviour and logic tasks
Impairs alertness
How does a normal brain deal with dangerous situations?
Understanding complex situations and ignoring irrelevancies
Assessing risks and consequences
Communicating well, and showing lateral thought and innovation
What happens when rats are sleep derived?
Die within 20 days = cause not clear, become lethargic, lose weight despite eating more, develop skin ulceration and injury, no physical cause of death
How does sleep deprivation lead to RTAs?
About 10% of RTAs are sleep related = most are acutely sleep deprived
truck driver falling asleep is most likely cause of accidental death at work
How much sleep is needed for normal function?
Most studies suggest 7-7.5 hours a night is acceptable
How effective is it to take a nap during the day?
A mid-afternoon nap of 15mins is equivalent to 90mins overnight
What are some examples of non-REM parasomnias?
Non-dreaming, confusional arousals, sleep walking, sleep paralysis, bruxism, restless legs and PLMS
What are some features of REM parasomnias?
Often seen preceding Parkinson’s disease
Usually later third of night
Much simpler behaviour with dreaming
What is the epidemiology of narcolepsy?
Two peaks of incidence = age 15 and 36
Equal sex distribution
What features characterise narcolepsy?
Daytime sleepiness, cataplexy, sleep paralysis and RBD
What is daytime sleepiness?
Involuntary somnolence during eating or talking
What is cataplexy?
Loss of muscle tone = triggered by emotion, occurs in 70% of patients
How long does it take to diagnose narcolepsy?
Typical 10 year delay between onset and diagnosis
50% of adults report symptoms beginning as teenager
What investigations can be done for narcolepsy?
Overnight polysomnography, multiple sleep latency test, lumbar puncture
How is a multiple sleep latency test carried out?
Four 25 minute naps scheduled 2 hours apart
record EEG, muscle activity and eye movement
Measures time from start of daytime nap to first signs of sleep
What is the lumbar puncture result of a patient with narcolepsy?
Low CSF hypocretin levels = <110 pg/ml
What impact does narcolepsy have on driving?
Must stop driving cars until controlled
Permanent exclusion from driving group 2 vehicles
What is insomnia?
Psychophysiological concept = alertness around sleep
