2. Neural Basis of Sleep Flashcards
1
Q
electroencephalogram
A
- EEG = measures electrical brain activity from the scalp
2
Q
electrooculargram
A
- EOG = measures eye movements
3
Q
electromyogram
A
- EMG = muscle activity (usually chin or legs)
4
Q
polysomnography
A
- PSG = all the techniques used to record information about sleep
- objective measure often delivered with a sleep survey
5
Q
delta
A
< 4Hz
> 50Mv
6
Q
theta
A
4-7Hz
10-50Mv
7
Q
alpha
A
8-13Hx
5-15Mv
8
Q
beta
A
> 13Hz
< 5Mv
9
Q
frequency and amplitude
A
- used to classify different levels of arousal and sleep states
10
Q
frequency
A
amount of oscillations in a given time (a second)
11
Q
amplitude
A
size of oscillation
12
Q
sleep-wake regulation
A
- many neurotransmitters involved in sleep, some excitatory and others inhibitory (some stabilising neuromodulators)
- all help govern sleep
- psychiatric disorders often have impairments in these
13
Q
excitatory neurotransmitters
A
- Acetylcholine
- Dopamine
- Histamine
- Noreadrenaline
- Serotonin
14
Q
inhibitory neurotransmitters
A
- Galanin
- GABA
15
Q
neuromodulators
A
- hypocretin (orexin)
16
Q
pineal
A
- gland found in the thalamus
- produces melatonin
- feeds back on master clock and gives a biological representation of the dark as it is released at night
- light blocks melatonin, interacting with the circadian rhythm by blocking sleep
- light also has an alerting effect
- keeps us aligned to local time
17
Q
diurnal
A
active during the day
18
Q
nocturnal
A
active during the night
19
Q
how do we know when to sleep?
A
- circadian rhythms
- function of living organisms that display a rhythm of about 24h (sleep)
- different structures and processes take place over the 24h cycle (hormones, skin repair, appetite)
- sleep wake regulation - suprachiasmatic nucleus
- homeostasis
- Pineal
20
Q
sleep wake regulation
A
- suprachiasmatic nucleus
- internal representation of time
- if destroyed there is no 24h rhythm
- SCN neurons display 24h cycle even after removed
- SCN is an internal clock with all cells having a 24h cycle, this is how we control our circadian rhythm
- circadian rhythm particularly sensitive to light (sets clock)
- Ibuka & Kawamura (1975)
- Zaidi et al (2007)
21
Q
Ibuka & Kawamura (1975)
A
- lesions the SCN in rats
- found that the rats no longer had regulation in their 24h rhythms
22
Q
exogenous zietgebers
A
External cues which regulate our internal body clock
23
Q
endogenous pacemaker
A
internal mechanisms that govern biological rhythms, in particular the circadian sleep/wake cycle
- E.G. the SCN
24
Q
Zaidi et al (2007)
A
- even if you are blind you can still entrain your internal clock through light
- melanopsin in photo-sensitive retinal gangloin cells does this (SCN depends on these exogenous zietgebers)
25
homeostasis
= sleep pressure (need for sleep)
- works with biological and circadian clock to regulate
- as homeostatic drive for sleep increases, circadian drive for arousal decreases
- this resets the next day
26
sleep pressure
= build up of adenosine
- when ATP is broken down adenosine is the bi-product
- as ATP is used throughout the day adenosine builds up
- end of day = highest levels of adenosine (resets next day; Moore, 2007)
27
awake (stage)
- alpha > beta
- high frequency
- low amplitude activity
28
stage 1
- nodding off
- theta activity = very relaxed
- drop in HR and body temp
- muscles start to relax
29
stage 2
- transition to deep sleep
- sleep spindles (bursts of activity) from thalamus projecting to cortex (thought to play a role in memory consolidation)
- 12-14Hz trains of high frequency waves thought to inhibit processing to keep the individual in a tranquil state
- k complexes also found
30
k complexes
- brain and body trying to stop anything external waking you up
- trying to get you into a deep sleep
- transition
- BIPHASIC wave that stands out from the rest of the EEG recording
31
stage 3 and 4
- moving towards deeper sleep
- transitioning to delta activity
- large amplitudes = slow wave sleep = groups of neurons firing at the same time, synchronising in a collective way
- night terrors occur if woken here
- very popular stages of research (memory consolidation)
32
REM
- similar to when awake
- EOG large due to moving eyes
- EMG - little of no activity as almost paralysed (would act out your dreams otherwise)
- important in managing emotions and processing information from the day
33
the cycle
- fall asleep > skip REM sleep and straight into stage 1
- first cycle a lot of time is spent in stage 4 sleep
- back out into REM = 1 cycle
- 5 cycles roughly in a night (each approximately 90 minutes)
- deeper stages reduce as night progresses
- REM sleep increases as night progresses, often wake in this stage (sometimes not remember they woke)
34
reticular activating system
- ascending arousal system = excitatory neurotransmitters keep us awake as they inhibit the sleep cycle
- this includes acetylcholine, dopamine, histamine, noreadrenaline and serotonin
- hypocretin (orexin) 'flips the switch' on the sleep cycle
35
hypothalamic sleep system
- primary inhibitory (sleep promoting) system located in the ventrolateral preoptic area of the hypothalamus (VLPO)
- inhibits arousal system (excitatory neurotransmitters
36
hypocretin (orexin)
- hypocretin (orexin) 'flips the switch' on the sleep cycle (synthesised in the hypothalamus)
- hypocretin promotes wakefulness, inhibitory neurotransmitters block it (indirectly inhibited by adenosine)
37
how do the neurotransmitters promote sleep and wakefulness
- noreadrenaline (NA), serotonin (5-HT), dopamine (DA), histamine (his), hypocretin/orexin (Orx), Acetylcholine (Ach) all innervate the cortex as they are excitatory
- as adenosine builds throughout the day, hypocretin is inhibited
- inhibitory neurotransmitters from the ventrolateral preoptic area of the hypothalamus (VLPO) include GABA and Galanin - they then inhibit all of the excitatory neurotransmitters and sleep follows
