EEG, Sleep And Circadian Rhythms Flashcards
What is the definition of sleep
State of unconsciousness from which individual can be aroused by normal stimuli, light, touch, sound etc.
Sleep is predictable and cyclical
What is a coma
State of unconsciousness from which individual cannot be aroused and does not respond to stimuli
COMA IS NOT DEEP SLEEP
Where does the active inhibitory process that induces sleep occur
Pons
Destruction of brainstem at level of mid-pons creates a brain that never sleeps
What molecules contribute to sleep (4)
Delta sleep inducing peptides (DSIP)
Adenosine
Melatonin
Serotonin
What is the role of the suprachiasmatic nuclei (SCN) in induction of sleep
SCN has a 24hr circadian rhythm controlling the release of melatonin from the pineal gland
What does light and darkness do to the SCN
Inhibitory neurons in SCN are stimulated by light and act to inhibit pineal gland, therefore no melatonin is released
Darkness removes the inhibition, stimulating the pineal gland —> increased melatonin release —> feeling sleepy
What is the role of serotonin in sleep (how is this linked to treating depression)
Serotonin it’s a precursor of melatonin production
Serotonin selective reuptake inhibitors (SSRI’s) are a common treatment for depression where sleep disruption is often present - act to increase serotonin levels in synapse
What is an electroencephalogram (EEG)
A recording of brain activity
What happens to the frequency and amplitude of the waves on an EEG with increasing neuronal excitation
Frequency increases with increasing neuronal excitation
Amplitude decreases with increasing neuronal excitation
What is stage 1 of the sleep cycle
Stage 1: slow wave, non-REM, S-Sleep
Slow eye movements, light sleep very early in the sleep cycle. Easily roused. High amplitude, low frequency
What is stage 2 in the sleep cycle
Eye movements stop, frequency lows further but EEG shows bursts of rapid waves called “sleep spindles”
what is stage 3 of the sleep cycle
High amplitude, very slow waves interspersed with short episodes of faster waves
Spindle activity declines
What is stage 4 of the sleep cycle
Exclusively delta waves
What are stage 3 and 4 of the sleep cycle known as (what characterises them)
Known as deep sleep
Very difficult to rouse from stage 3 & 4 - sleep walking/talking occurs in these stages
What happens after stage 4 sleep
Move back up through stage 3 and 4 before entering REM sleep
What is REM sleep
REM = rapid eye movements
Dreams occur during REM sleep
25% of sleep is REM
Low amplitude high frequency waves - eerily similar to awake state
What happens to amplitude and frequency as you move through the stages of sleep
Increasing amplitude and decreasing frequency
What does typical pattern of nights sleep in healthy young adult look like (no answer photo only)
What are the physiological characteristics of deep sleep (stage 4) (4)
Deep sleep that occurs in first hours of sleep
Most restful type of sleep
Associated with decreased vascular tone (and therefore BP), respiratory and basal metabolic rate (hence drop in BP)
Hippocampus very active (making new memories)
What are the physiological characteristics of REM sleep (4) (how long does it last and how often)
Lasts 5-30 minutes every 90 minutes
1. Dreams occur in REM sleep due to new neuronal connects being made
2. Eye muscles show bursts of rapid activity (profound inhibition of all other skeletal projections to prevent acting dreams out)
3. EEG pattern mimics beta waves associated with highly alert awake state
4. If deprived of REM sleep, there is a catch up when able to sleep again
How does time spent sleeping change as you grow up
Time spent sleeping decreases rapidly through childhood and adolescence
Percentage of REM sleep also declines (may be absent 80+ years)
What is insomnia
Chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
What is the difference between chronic primary insomnia and temporary secondary insomnia
Chronic primary: no identifiable psychological or physical cause
Temporary secondary: in response to pain, bereavement or other crisis (usually short lived)
What are nightmares
Strong visual component seen during REM sleep, typically occur quite far on through the night. waking will stop the nightmare and the individual will have a clear recollection of the “dream”
What are night terrors
Occur in deep delta sleep common in children. Typically occur early in the night.
Children thrash and scream and may sit/stand up with their eyes open but aren’t properly awake
Doesn’t remember episode upon waking following morning
What is somnambulism (sleep-walking)
Occurs exclusively in non-REM sleep (mainly stage 4)
Sleep walkers appear awake - eyes open, see and will avoid objects, carry out reasonably complex tasks such as preparing food and will often obey instruction but have no recollection when woken
What is narcolepsy
Enter directly into REM sleep with little warning
Very dangerous because of accident risk (e.g. driving)
Occurs due to dysfunctional orexin release from hypothalamus
