EEG, Sleep and Circadian Rhythms Flashcards
Where in the brain does sleep occur and why ?
The reticular formation within the Pons
This area is said to be Serotonergic - any medication which blocks serotonin can inhibit sleep
What is the suprachiasmatic nuclei (SCN) and what is its role in sleep ?
Is found within the hypothalamus and is involved in the induction of sleep, it demonstrates the 24-hour circadian rhythm
The stimulation of the SCN causes the release of _____ from the ________
Melatonin
Pineal gland
What is the neurotransmitter responsible for waking us up and where is released from ?
Orexin (Hypocretin)
Released from the SCN
Describe the waking cycle
- Excitatory neurons in the ascending reticular activating system (ARAS) are released from inhibition from the sleep centres in the reticular formation.
- This release of the previously inhibited excitatory neurons will stimulate the excitatory pathways in the CNS and the PNS
What happens to the inhibitory neurons during sleep ?
They become fatigued and therefore the excitatory neurons have to take over
Describe the 5 stages of the sleep cycle
- Slow wave, non-REM sleep. Slow eyemovements. Light sleep and easily roused.
- Bursts of rapid waves called “sleep spindles”
- High amplitude waves, very slow delta-waves mixed with short episodes of faster waves (spindle activity declines)
- Exclusively delta waves
Which stages of sleep is it hardest to wake someone up ?
Stages 3 & 4
What happens to the waves as we go through the stages of sleep ?
Increasing amplitude and decreasing frequency
What are the 4 wave types present on EEG recordings ?
Alpha
Beta
Theta - low frequency and vary in amplitude
Delta - High amplitude and low frequency
Define insomnia
The chronic inability to sleep
Define Somnambulism
This is sleep-walking, usually occurs in non-REM sleep
Define what is meant by circadian rhythms
The SCN of the hypothalamus lies just above the optic chiasm
