EEG, Sleep and Sleep disorders Flashcards
What are the four main types of brain wave that can be seen on an EEG?
Alpha (8 - 13 Hz)
Beta (14 - 30 Hz)
Theta (4 - 7 Hz)
Delta (<3.5 Hz)
Describe how frequency and amplitude of EEG waves change in relation to neuronal excitation
Frequency generally increases with neuronal excitation
Amplitude generally decreases with neuronal excitation
How does REM sleep look on an EEG?
Looks like an awake state - beta waves (with some theta waves)
What do beta waves on an EEG indicate? What do they look like?
Awake and alert state
High frequency, low amplitude
Asynchronous
Why are beta waves asynchronous?
The brain is doing many things at once; opposing polarities cancel each other out
What to alpha waves on an EEG indicate? What do they look like?
Awake but relaxed state
High frequency, high amplitude
Waves are generally synchronised
What do theta waves look like on an EEC? What state do they indicate?
State: light sleep
Low frequency
Amplitude can vary widely
What do delta waves on an EEG indicate? What do they look like?
State: deep sleep
Very low frequency but high amplitude
Which part of the brain is thought to control circadian rhythms?
Suprachiasmatic nuclei in the hypothalamus
How much of sleep is REM?
25%
What are sleep spindles?
1-2 second bursts of rapid brain activity
Occur during stage 2 of sleep
What are K complexes?
Very high amplitude waves that occur during stage 2 of sleep
Which stages of sleep are referred to as slow wave sleep? What type of EEG waves primarily occur in these stages?
Stages 3 and 4
Delta waves; stage 3 is mainly slower, larger theta waves with delta waves interspersed, whereas stage 4 is almost exclusively delta waves
Which neurotransmitter is involved in REM sleep?
Acetylcholine
Describe the aetiology/pathophysiology of narcolepsy
Dysfunctional orexin release from the hypothalamus due to loss of orexin-secreting neurones
Which stage of sleep to narcoleptic patients generally enter into?
They enter directly into REM sleep
What is somnambulism? In which stage(s) of sleep does it occur?
Sleepwalking
Occurs only in non-REM sleep, mainly in stage 4 (slow wave sleep)
Why does the prevalence of somnambulism decrease with age?
The amount of stage 4 sleep decreases with age; this is primarily when somnambulism occurs
Which neurotransmitter is involved in narcolepsy?
Orexin
- defective orexin signalling caused by loss of orexin-secreting neurones in the hypothalamus
What is cataplexy?
Similar to sleep paralysis but occurs during the day. Often triggered by strong emotions.
Why does sleep apnoea cause daytime sleepiness?
Frequent waking due to apnoea means that the slow wave sleep stages are not reached
Which neurotransmitter is required for wakefulness?
Orexin
these neurones stop firing during sleep
Describe the pharmacological management options for insomnia
Can be used for up to two months while waiting for other management methods such as behavioural therapy to take effect.
- Melatonin-agonists
- Non-benzodiazepine sedatives
- Benzodiazepines (occasionally)
How prevalent is sleep apnoea?
Affects 1 in 20 adults
Describe the management of narcolepsy
Adopt a regular sleep routine
Avoid excess caffeine and alcohol
Drug treatment: dexamfetamine and modafinil
