Modulatory and arousal systems Flashcards
1
Q
Specific vs modulatory pathways
A
- specific = precisely localised. sensory, motor, cognitive processing. fast transmission - ionotropic
- modulatory = diffuse systems. control state of system. non-specific. slow - metabotropic
2
Q
Sleep-wake cycle - Awake vs Asleep
A
- Awake - thalamic cells relay sensory info to the cortex - fire when stimulated, desynchronised with low amplitude but high frequency
- Asleep - thalamic cell starts to fire bursts of AP in a rhytmic manner - no longer relaying the specific information. When the thalamic nerves start to fire, the inhib. intern. start to control them. - peaks and troughs at regular intervals, high amplitude but low freq.
3
Q
Slow wave sleep
A
- Stages 3 and 4
- gradual increase in amplitude and reduction in frequency as you move into deeper sleep
- less than 4Hz with a high amp. at deepest sleep
- increase in synchronisation in thalamus and cortex
4
Q
REM sleep - EEG
A
- EEG looks like you are awake - low amp. and high freq.
- completely limp and paralysed but your eyes move around
- dreaming
- through the night, REM gets longer and NREM gets shorter and shallower
5
Q
Acetylcholine pathway
A
- Pathways from the pontomesencephalic tegmentum (grey matter in pons and midbrain) go to the basal forebrain, neocortex and hippocampal complex and the thalamus and basal ganglia
- ACh increases response strength and selectivity and increases plasticity of the brain
- causes us to be awake and attentive, increases cognition, learning and memory
- desynchronises thalamic cells > connection to outside world
- a lack of ACh leads to cognitive decline and memory issues
- AChE inhibitors such as Donepezil reduce ACh breakdown (used in AD)
6
Q
NA pathway
A
- used everywhere, extends in a long stripe from locus coeruleus downwards
- NA increases response amplitude and selectivity
- causes us to be awake and vigilant, alert to new stimuli, increases learning and memory and controls mood
- A lack of NA leads to anxiety and depression
- NA reuptake inhibitors and MAOIs can increase NA levels
7
Q
DA pathway
A
- Also associated with areas of the thalamus
- Substantia nigra projects to the basal ganglia
- ventral tegmental area projects to the frontal cortex, limbic and related structures (amygdala and nucleus accumbens)
- DA causes us to be awake, alert to rewarding/aversive stimuli, adaptive behaviour
- Too much DA > sz
- Too little > PD
8
Q
Histamine pathway
A
- released from hypothalamus (tuberomamillary nucleus)
- spreads to the thalamus and cortex
- it excites wake-promoting circuits - makes us awake and alert
- anti-histamines > drowsiness
9
Q
Orexin (hypocretin) pathway
A
released from hypothalamus and spreads everywhere in brain
- excites wake-promoting circuits, responds to nutritional status and linked to reward centres
- causes us to be awake and exploring, allows energy homeostasis
- low orexin > narcolepsy
10
Q
Serotonin (5-HT) pathway
A
- released from raphe nuclei to everywhere in brain
- causes quiet waking, appropriate response to stress, mood and helps analgesia pathway
- reduced levels lead to anxiety and depression
- can take SSRIs or MAOIs to reduce anxiety and depression
11
Q
Arousal: From sleep to wake
A
- Hypothalamus releases orexin and histamine
- increases activation of brainstem
- releases serotonin, ACh and NA > desynchronises EEG
- increases activation of the basal forebrain, which releases more ACh > increased response strength and selectivity
- brain stem lesions > coma
12
Q
Falling asleep
A
- hypothalamus (ventrolateral preoptic nucleus) releases GABA
- reduces the levels of orexin and histamine released from the hypothalamus and the serotonin, ACh and NA released from the brain stem
13
Q
What activates the Ventrolateral preoptic nucleus?
A
- Circadian rhythm (SCN)
- tiredness (build up of adenosine
- illness (increase in immune by-products)
- caffiene is an adenosine antagonist > reduces tiredness
- Lesions in GABAergic centre cause insomnia
14
Q
REM Sleep
A
- increased levels of ACh, with decreased levels of other chemicals
- ACh increases basal forebrain activity among other areas
- increases activity in higher cortical areas > dreaming
- Causes desynchronised EEG (like if awake) however also causes skeletal muscle paralysis
15
Q
Modulatory pathways control cognitive performance
A
- stimulation of histamine, NA, serotonin, DA and orexin systems in brain
