EEG, Sleep, and Circadian rhythms Flashcards
why does sleep occur?
due to active inhibitory processes that originate in the pons
where in the brain does evidence suggest that the activity required for sleep occurs?
reticular formation of the pons
why do drugs that block serotonin formation inhibit sleep?
serotonin is critical to sleep induction
what part of the diencephalon does evidence suggest is vital to sleep?
hypothalamus
what is the effect of electrical stimulation of the suprachiasmatic nuclei of the hypothalamus?
promotes sleep
what can damage to the suprachiasmatic nuclei cause?
disruption of the sleep-wake cycle
what neurotransmitter released by the hypothalamus is essential for wakefulness?
orexin
what condition is associated with defective orexin signalling?
narcolepsy
what is the ascending reticular activating system a part of?
the reticular formation
what happens to excitatory neurones in the ARAS during wakefulness?
the are released from inhibition from sleep centres in the reticular formation
what do the excitatory neurones in the ARAS stimulate?
excitatory pathways of the CNS and PNS
what happens when the active cells of the CNS and PNS become fatigued?
excitatory signals fade and inhibitory peptide signals from the sleep centres in the reticular formation take over
what is the effect of the sleep centres in the reticular formation when they release inhibitory peptides?
rapidly inhibit the weakening excitatory signals leading to the rapid progression into the sleep state
what are some methods of assessing the level of consciousness in an awake person?
look at: behaviour general alertness speech patterns speech content reading writing calculating skills perform an electroencephalogram
what are 2 ways in which EEG wave patterns can be analysed?
amplitude
frequency
what are the 4 main types of wave patterns on an EEG?
alpha
beta
theta
delta
when would you expect to see alpha waves on an EEG recording and what do alpha waves look like?
in a relaxed, awake state, you would expect to see the high frequency high amplitude alpha waves
when would you expect to see beta waves on an EEG recording and what do beta waves look like?
in the alert awake state, beta waves are very high frequency, low amplitude waves
why are beta waves low amplitude?
the increase in brain activity is asynchronous as the brain is doing so many things at once and the opposing polarities of the signals cancel each other out and do not get recorded on the EEG
what are theta waves characterised and when would you expect to see them?
low frequency waves which vary enormously in aplitude. common in children and during times of emotional stress and frustration in adults. also occur in sleep in both children and adults
what are delta waves characterised by and when do they occur?
low frequency and high amplitude, they occur in deep sleep
what is stage 1 of the sleep cycle characterised by?
slow eye movements
easily roused
high amplitude, low frequency theta waves