EEG, sleep and circadian rhythms Flashcards
Define sleep.
Stage of unconsciousness from which individual can be aroused by normal stimuli e.g. light, touch, sound.
->Predictable and cyclical
Define coma.
State of unconsciousness from which individual cannot be aroused and does not respond to stimuli.
What symptoms arise if someone is deprived of sleep?
-Impairment of cognitive function
-Impairment of physical performance
-Sluggishness
-Irritability
List some of the things that sleep supports/
- Neuronal plasticity
- Learning and memory
- Cognition
- Clearance of waste products from CNS
- Conservation of whole body energy
- Immune function
->suggested we sleep more when we are ill do to it helping immune function
What does neuronal plasticity allow?
Learning and memory.
New neural connections in brain forming
In which part of the sleep phase are we in our deepest sleep?
Early stages of sleep phase
When are new neuronal connections made?
Late phases of sleep
->early phase prunes back connections which have already been made
In which part of the sleep do we dream the most?
Late phases
Which area of the brain brings about sleep (as far as evidence suggests)?
Reticular formation of the brainstem
->known it occurs at some point below the pons
Name some molecules which are believed to contribute to sleep.
Delta sleep inducing peptides (DSIP)
Adenosine
Melatonin
What happens as adenosine levels build up during the day?
Feeling of sleepiness develops- known as sleep pressure
What antagonises adenosine receptors?
Caffeine
->why it keeps you awake
Where is melatonin produced?
Pineal gland
What is the pineal gland under the influece of?
Suprachiasmatic nuclei
Where is the suprachiasmatic nuclei found?
Hypothalamus
What does the SCN (suprachiasmatic nuclei) demonstrate?
24hr circadian rhythm
What does the SCN control the release of?
Melatonin
What are the inhibitory neurons in the SCN stimulated by?
Light
->therefore darkness removes inhibition and we get stimulation of pineal gland and melatonin release allowing us to sleep :)
What is orexin?
An excitatory neurotransmitter required for wakefullness
Where is oxerin released fron?
Hypothalamus
What inhibits orexin?
Melatonin
What does defective orexin signalling cause?
Narcolepsy-> individual will suddenly fall asleep, sometimes even when talking
Drugs that block the formation of serotonin (not a typo) have what kind of affect on sleep?
Disrupt sleep
During depression, a person can have lower levels of serotonin. How does his affect them?
Struggle to sleep
Therefore, which drugs are given to those with depression?
SSRI’s
->serotonin selective reuptake inhibitors
How can electrical activity in the brain be recorded?
Using EEG or electroencephalogram
How can the EEG waves be analysed?
By amplitude and frequency
In general, what happens to frequency with neuronal excitation?
Frequency increases
In general, what happens to amplitude with neuronal excitation?
Amplitude decreases
What is frequnxy?
Number of wave
What is amplitude?
Size of wave
In terms of sleep, the longer the wave..?
The deeper the level of unconsciousness
When will the frequency of waves be increased?
The more focused you are.
But awake means greater amplitude than being asleep.
What is abnormally fast EEG waves characteristic of?
Epilepsy
Name the four types of wave pattern seen
Alpha
Beta
Theta
Delta
What are alpha waves associated with?
Relaxed-awake state
What are beta waves associated with?
Alert awake state
What are theta waves associated with?
Early sleep
Wat are delta waves associated with?
Deep sleep
Describe the amplitude and frequency for alpha waves.
High frequency
Medium amplitude
Describe the amplitude and frequency for beta waves.
Very high frequency
Low amplitude
Describe the amplitude and frequency for theta waves.
Low frequency
Amplitude varies
Describe the amplitude and frequency for delta waves.
Very low frequency
High amplitude
Why is there low amplitude seen in the beta waves when the person is in the awake-alert phase?
Low amplitude does not reflect low activity. Heightened alert state but as brain doing so many things at once, the opposing signals cancel each other out and are not seen on EEG.
Sleep in cyclical and has five stages. The first stage can be called slow wave sleep. Describe slow wave sleep
Light sleep very early on in the cycle.
Easily aroused.
Describe the amplitude and frequency seen in slow wave sleep.
High amplitude
Low frequency
Which type of wave is seen in slow wave sleep?
Theta waves
Describe the amplitude and frequency in stage 2 in which the eye movements stop.
Frequency slows further but shows bursts of rapid waves called sleep spindles.
Describe the amplitude and frequency in stage three.
High amplitude
Very slow waves (low frequency) with a few short episodes of fast waves. However, spindle activity declines.
Which type of waves are seen in EEG of stage three of sleep?
Delta
Which type of fibres are seen in stage four of sleep?
Only delta fibres
In which stages of sleep is it very hard to rouse people?
Stages 3 and 4- known as deep sleep
In which stages does sleep walking/talking occur?
Stage 3/4
What happens after stage 4 sleep?
Move back to stage three, then two before entering REM sleep
What is REM sleep?
Rapid eye movement sleep
When do dreams occur?
REM stage of sleep
What % of sleep is REM sleep?
25%
Describe the amplitude and frequency seen in REM sleep.
Low amplitude
High frequency
->eerily similar to waves seen when awake
Therefore, the large amplitudes are associated with what?
Deepest stages of sleep
The cycle of sleep is very predicable as the night goes on. Briefly expalin it.
Start with stage 1->2->3 to deep sleep, then back into 3 and 2, then REM then back down into deep sleep, back through 3 and 2, then REM, etc.
Look at graphs to fully get what I’m saying
As time asleep increases, what happens to REM?
Time spent in REM also increases
When does deep sleep occur?
First few hours of sleep, most restful type of sleep
What happens to the body in deep sleep?
Decreased vascular tone, BP, respiratory and metabolic rate
->this is why there is a drop in body temperature while sleeping
Name a part of the brain which is particular active during deep sleep- the slow wave sleep.
Hippocampus
If the hippocampus is damaged, what happens?
Person unable to make new memories but keeps old memories.
How often does REM sleep occur?
Every 90 mins during sleep, lasts for 5-30 min
In REM sleep, there are rapid eye movements. There is inhibition of all other skeletal muscles due to what?
Inhibitory projections from the pons to the spinal cord
Why is there inhibition of all other skeletal muscles during REM sleep?
Prevents people from acting out dreams which occur in REM stage of sleep
Which types of pathways is REM sleep dependant on?
Cholinergic pathways within the reticular formation
People taking anticholinesterases have increased time in which area of sleep?
REM sleep
How much time will a premature infant spend in REM sleep?
80% of sleep
How much time will a newborn infant spend in REM sleep?
50% of sleep
How much time will adulthood spend in REM sleep?
25% of sleep
How much time will an elderly person spend in REM sleep?
Very little, if any
As older people spend less time in REM sleep, what could this affect?
Cognitive function
Memory
How much sleep does an adult need a night?
8hrs
What is insomnia?
Common sleep disorder
Chronic inability to obtain the necessary amount or quality of sleep required to maintain adequate day time behaviour
It is important to distinguish between types of insomnia like:
-Chronic, primary insomnia
-Temporary, secondary insomnia
What causes chronic primary insomnia?
Often no identifiable psychological or physical cause
What cause temporary secondary insomnia?
Pain, bereavement, other crisis
Usually short lived
Give some examples of behaviours which promote sleep.
Avoiding use of screens
Avoid caffeine
Avoid vigorous exercise late in evening
When do nightmares occur?
REM sleep
Nightmares have a strong visual component. What stops the nightmare?
Waking up
When in sleep do night terrors occur?
Deep, delta sleep
In which age range of children can it be common to see night terrors?
Age 3-8
What may be seen in a child with night terrors?
Thrashing and screaming, open eyes, unable to recognise parents
Do children remember night terrors when they wake up?
No
Do people remember nightmares when they wake up?
Yes
Somnambulism?
Sleep walking
In which stage of sleep does somnambulism occur?
Non-REM sleep, mainly stage 4 sleep
Describe what is seen when a person in sleep walkig.
Appear awake, eyes open, avoid objects, carry out reasonably complex tasks and can obey instructions
Will people who sleepwalk remember in the morning?
No
What happens in narcolepsy?
Individual enters directly into REM sleep with little walking
When could narcolepsy be dangerous?
Driving etc. as fall asleep with no warning
