17/ sleep and circadian rhythms Flashcards
1
Q
what areas does sleep change
A
- behaviour - posture change, less responsive to stimuli, move less
- change in brain activity
- structural changes
- gene expression - some genes over/under expressed
2
Q
what 2 broad cycles make up sleep
A
REM and non-REM
2
Q
how can you measure muscle movements, eye movements and brain activity during sleep
A
- electromyography
- electro-oculography
- electroencephalography
2
Q
how does an electroencephalogram work, what are the resolutions like
A
- measures synchronous electrical activity from LARGE pops of neurons in brain - millions
- caused by cellular, ionic movements, which create an electric field
- electrodes on scalp detect electric fields
- high temporal resolution - miliseconds
- low spatial res - so many neurons
2
Q
main types of brain waves, how do you have dif brain waves
A
- beta - fastest
- alpha
- theta
- delta - slowest
- generated by dif parts of brain
3
Q
what defines non REM sleep
A
- low neuronal activity
- metabolic rate and brain temp lowest
- hr and bp decreased - decreased sns outflow
- increase pns
- muscle tone and reflexes intact
3
Q
stage 1 of non rem sleep
A
- 1 drowsiness.
- awakened easily, eyes move slowly, muscle activity slows, sudden muscle contractions and sensation of falling
- lasts mins
- increased sinusoidal alpha activity on EEG as awake people relax
- mostly characterised by low voltage activity w mixed frequency, mostly theta waves on EEG
3
Q
STAGE 2 of non rem
A
- 2 light sleep
- eye movements stop, brain waves slower w occasional burst of rapid brain waves
- body preps for deep sleep
- body temp drops, hr slows
- characterised by bursts of sinusoidal waves - sleep spindles - and biphasic waves - k complexes
- k complexes occur episodically against background low voltage activity of EEG
4
Q
alternating between non rem and rem
A
- between stages there are body movements and partial arousals
- after 70-80 mins sleeper goes to stage 3 or 2 before entering 1st rem phase
- 1st rem phase lasts 8-10 mins
- time from 1st stage to end of rem = 90-110 mins
- repeated 4 or 5 times per night. during each cycle, stages 3 and 4 get shorter and rem gets longer
4
Q
stage 3 of non rem
A
- 3 deep sleep
- extremely slow delta waves interspersed w smaller, faster waves
- sleepwalking, night terrors, talking, bedwetting - parasomnia
- occurs between transition between non rem and rem sleep
4
Q
stage 4 of non rem
A
- 4 v deep sleep
- brain produces delta waves almost exclusively
- disorientation for several mins following arousal from 4
- slow wave activity increases and dominates EEG record
4
Q
stage 5/REM sleep
A
- EEG mimics wakefulness/stage 1 - low voltage mixed frequency - paradoxical sleep
- rem found in birds
- closed eyes move rapidly side-side
- perhaps related to intense dream and brain activity
- brain temp and metabolic rate rise - increased neuronal activity
- all skeletal muscles are atonic- flaccid and paralysed - otherwise you’d move too much, dangerous
- muscles controlling eye movenets and middle ear ossicles and diaphragm remain active - so you can breathe and hear danger
5
Q
% of times spent in each stage in young adults
A
- 1: 5%
- 2: 50-60%
- 3 and 4: 15-20%
- 5/ rem: 20-25%
5
Q
how is sleep regulated
A
- release norepinephrine and serotonin/5ht in brain stem
- diffuse modulatory neurotransmission systems controls rhythmic behaviours in thalamus
6
Q
wakefulness behaviour
A
- lesions of brain stem can cause sleep and coma
- activation of neurons in the brain stem precedes awakening
- stimulation of brain stem causes awakening - depolarising
6
Q
non rem stage activity of neurons in thalamus
A
- decrease of firing in brain stem
- spindles - correlated activity in thalamus
- delta rhythms - activity in thalamus
7
Q
rem stage neurons and brain
A
- similar to firing awake
- no activity in frontal lobe
- no activity in raphe nuclei and locus coeruleus
- inhibition of motor neurons
8
Q
dreaming theories
A
- strange imagery - brain not fully functioning
- exercises synapses when no external activity
- circuit testing
- memory consolidation - short to long term
8
Q
circadian rhythm, duration, influenced by
A
- 24h
- persist without environmental cues
- but are modulated by external timing cues - zeitgebers - which adapt rhythm to envrionment
8
Q
where is the major internal clock
A
- suprachiasmatic nucleus of the anterior hypothalamus
- regulates timing of sleep, not sleep itself
- rentinohypothalamic tract. lesioning of this dampens down circadian rhythm
- intrinsically photosensitive ganglion cells provide input to suprachiasmatic nucleus - why removing eye no longer recommended
