Sleep Flashcards
where does the sleep process originate?
the pons, reticular formation
what is the difference between sleep and coma?
in sleep a person can be aroused with normal stimuli (light, noise, touch) but in a coma they cant
what can electrical stimulation of the suprachiamatic nuclei promote?
sleep
what is orexin?
excitatory neurotransmitter released by the hypothalamus that is required for wakefulness
what can defective orexin signalling cause?
narcolepsy
describe the positive feedback from the CNS and PNS that sustains wakefulness
> excitatory neurons in ascending reticular activating system (part of the reticular formation) are released from inhibition from sleep centres
this stimulates excitatory pathways in the CNS and PNS
this becomes a positive feedback system
what happens when excitatory signals fade and cells become fatigued in the positive feedback wakefulness system?
inhibitory peptide signals form the sleep centres in the reticular formation take over and rapidly inhibit the weakening excitatory signals leading to rapid progression into the sleep state
in an eeg recording what does the frequency increase with?
neuronal excitation
name the four main types of wave pattern seen on an eeg
> alpha
beta
theta
delta
what waves would you expect to see on an eeg in a relaxed awake state?
high frequency, high amplitude, alpha waves
describe eeg waves seen in someone in an alert awake state
very high frequency with a low amplitude, beta waves
why is low amplitude seen in beta waves on an eeg?
the person is alert and awake and the increase in activity is asynchronous as the brain is too busy. opposing polarities of signals cancel each other out and do not get recorded
what are theta waves?
these are low frequency waves which can vary in amplitude. they are common in children and are seen in emotionally stressed adults. they also occur during sleep
what waves occur in very deep sleep?
delta waves
describe delta waves
very low frequency but high amplitude
what is stage 1 of the sleep cycle?
> slow wave
slow eye movements
light sleep, easily rousable
high amplitude, low frequency theta waves
describe stage 2 of the sleep cycle
> eye movements stop
frequency slows
bursts of rapid waves called sleep spindles
describe stage 3 of the sleep cycle
> high amplitude, very slow delta waves
interspersed with short episodes of faster waves
spindle activity declines
what stage of sleep is exclusively delta waves?
stage 4
from what stage of sleep is it difficult to rouse someone and walking/talking can occur?
stages 3 and 4
what is the 5th stage of sleep?
> REM sleep
fast waves (similar to being awake)
dreams occur during rem sleep
what is associated with deep slow wave sleep occurring in the first few hours of sleep?
decreased vascular tone, respiratory and basal metabolic rate
describe eeg waves during rem sleep
> desynchronised
high frequency
low amplitude
what inhibits skeletal muscles in REM sleep?
inhibitory projections form the pons to the spinal cord
what is rem sleep dependent on?
cholinergic pathways within the reticular formation and their projections to the thalamus, hypothalamus and cortex.
what does anticholinesterases increase?
time spent in REM sleep
what is the effect of REM sleep on heart and respiratory rate?
they become irregular
what do sleep deprive subjects demonstrate without exception?
> impaired cognitive ability
impaired physical performance
sluggishness
irritability
what does sleep support?
> neuronal plasticity > learning and memory > cognition > clearance of waste products from central nervous system > conservation of whole body energy > immune function
define insomnia
chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
what must you distinguish in insomnia?
whether it is chronic, primary insomnia or temporary secondary insomnia
what are the negative effects of benzodiazepines?
they are addictive and cause problems on withdrawal
what is somnambulism?
sleep walking
in what stage does somnambulism occur?
exclusively in non-REM sleep and mainly in stage 4
describe narcolepsy
patients enter directly into REM sleep with little warning. it is linked to dysfunctional orexin release from the hypothalamus
where is the “master clock” of cardiac rhythm located?
in the suprachiasmatic nucleus of the hypothalamus just above the optic chiasma
what entrains 24 hour cycle in neurons in the suprachiasmatic nucleus ?
external clues such as dark and light cycles
what happens if the suprachiasmatic nucleus is destroyed?
circadian rhythm is lost
