EEG, Sleep and Circadian Rhythms Flashcards
What does activity of the suprachiasmatic nuclei control?
Release of melatonin from the pineal gland
What are inhibitory neurons in the suprachiasmatic nucleii stimulated by?
Light
Inhibit pineal gland
What is orexin?
Excitatory neurotransmitter released from hypothalamus
What is orexin required for?
Wakefulness
What does defective orexin cause?
Narcolepsy
How is level of consciousness assessed in an awake person?
Looking at behaviour, alertness, speech patterns and contents, reading, writing and calculating skills
Recording EEG
What is the amplitude of an EEG wave?
Size of the wave
Ranges from 0-200uV
What is the frequency of an EEG wave?
Number of waves per second
Ranges from 1-50+
What is the effect of EEG wave frequency with neural excitation?
Frequency of waves increase
What is the effect of amplitude of an EEG wave with neural excitation?
Amplitude decreases with increasing neuronal excitation
What are the 4 main types of wave pattern seen in an EEG?
- Alpha
- Beta
- Theta
- Delta
What type of wave pattern is seen in the relaxed, awake state in an EEG?
Alpha waves
What type of wave pattern is seen in the alert, awake state in an EEG?
Beta waves
What characterises alpha waves in an EEG?
High frequency
High amplitude
What characterises beta waves in an EEG?
Higher frequency than alpha
Low amplitude
Asynchronous waves
What characterises theta waves in an EEG?
Low frequency
Varied amplitude
When are theta waves in an EEG common?
In children
Emotional stress and frustration in adults
During sleep
What characterises delta waves in an EEG?
Very low frequency
High amplitude
When do delta waves in an EEG typically occur?
In deep sleep
What is stage 1 of a sleep cycle?
Slow wave Non-REM S-sleep Slow eye movement Light sleep - easily roused High amplitude, low frequency theta waves
What is stage 2 of a sleep cycle?
No eye movements
Frequency slows
Bursts of rapid waves (‘sleep spindles’)
What is stage 3 of a sleep cycle?
High amplitude, very slow delta waves
Short episodes of faster waves
Spindle activity declines
What is stage 4 of a sleep cycle?
Only delta waves
Deep sleep
When is sleep walking/talking most likely to occur?
During stages 3 and 4 of sleep cycle
What is stage 5 of a sleep cycle?
REM sleep
When dreams occur
25% of sleep
When does REM sleep occur?
Lasts 5-30 minutes every 90 minutes during a normal nights sleep
Becomes more frequent throughout the night
When are dreams most likely to occur?
REM sleep
What prevents people acting out their dreams during REM sleep?
Inhibition of skeletal muscles due to inhibitory projections from pons to spinal cord
What muscles show bursts of rapid activity during REM sleep?
Eye muscles
What is REM sleep dependent on?
Cholinergic pathways in the reticular formation and projections to the thalamus, hypothalamus and cortex
How do anticholinesterases affect REM sleep?
Increase time spent in REM sleep
What happens to heart rate and respiratory rate in REM sleep?
Become irregular
What happens to brain metabolism in REM sleep?
Increases
What are the signs of sleep deprivation?
Impairment of cognitive function Impairment of physical performance Sluggishness Irritability Psychosis may also occur
What functions does sleep support?
Neuronal plasticity Learning/memory Cognition Clearance of waste products from CNS Conservation of body energy Immune function
What is insomnia?
Chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
When does temporary, secondary insomnia occur?
In response to pain, bereavement or other crisis
Usually short lived
What is the effect of barbiturates on sleep?
Depress REM and delta sleep
Chronic use = increases time to fall asleep, decreases time spent in REM and stage 3 + 4 sleep
Increases number of times awake during night
What is the main issue with benzodiazepines?
Addictive which can cause problems on withdrawal
What are the risks of taking hypnotic sleeping drugs?
Increased risk of RTA and fall fractures
Risk of dementia is increased 3+ months use
What is the preferred approach to dealing with insomnia?
Behavioural changes to support induction of sleep
When are night terrors most likely to occur?
In deep delta sleep
Common in 3-8 year olds
Occur early in the night
What happens during night terrors?
Children thrash and scream
May sit/stand with eyes open
Child does not remember episode on waking
When does sleep-walking occur?
Exclusively in non-REM sleep
Mainly in stage 4
More common in children and young adults
What are the common actions of a somnambulist?
Walk with eyes open
Avoids objects
Completes complex tasks
Obey instructions
What is narcolepsy?
Person enters directly into REM sleep with no warning
