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physiology 3 > regulation of cortical excitability > Flashcards

regulation of cortical excitability Flashcards

1
Q

no cortical excitation

A

coma

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2
Q

cerebullum needs

A

constant activation by lower centres

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3
Q

brainstem compression creates

A

coma

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4
Q

2 forms of cortical stimulation

A

direct neuronal stimulation

neurohormonal systems

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5
Q

reticular formation

A

ascends brainstem and reticulates out
effective distribution system through the brain
can be used to directly deliver acetyl choline

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6
Q

reticular excitatory area

A

sits below the reticular formation

goes through the thalamus and into every region of the cortex

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7
Q

reticular inhibitory area

A

turns out the reticular excitatory area

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8
Q

what feeds into excitatory area

A

sensory information from the rest of the body

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9
Q

what is the REA - reticular exctatory system - for

A

general area/system for control off the overall level of excitaton of the brrain
sends signals upward and downwards

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10
Q

why does the REA send signals downward

A

for posture - control strength of reflexes and tension in anti gravity muscles

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11
Q

signals from the REA being sent upward through the thalamus (two signals)

A
  1. direct neuronal - rapid transmission (ms) to excite the cerebrum
  2. neurohormonal - build up progressively for s (minutes)
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12
Q

rapid transmission to excite cerebrum

A

uses gigantocellular neurones - excitatory
used ACh
rapidly acting, rapidly destroyed by acetyl cholinesterase

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13
Q

nuerohormonal transmission

A

build up progressively (seconds to minutes)
large number of smaller neurones, slower signal, also often excitatory (monoamines NA, DA)
controls longer term excitation of the brain

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14
Q

reticular inhibitory area is located in

A

medulla in reticular formation

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15
Q

reticular inhibitory area inhibits

A

excitation of the REA via serotonergic projections

5-HT is inhibitory - supresses using serotonin

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16
Q

4 types of neurohormonal control

A

noradrenaline system
dopamine system
serptonin syetm
acetylcholine system

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17
Q

noradrenaline system

A

locus coeruleus
mostly excitatory, fibres spread throughoout the cortex
active during wakefullness and non rem sleep
inactive during REM sleep

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18
Q

noradrenaline system s inactive during

A

REM sleep

19
Q

noradrenaline system is active during

A

wakefullness and non REM sleep

20
Q

dopamine system

A

excitatory or inhibitory (region dependant)

fibres innervate specific region

21
Q

serotonin system

A

produced in rephe nuclei
unually inhibitory, fibres to diencephalon and specific cortex regions
induction of sleep, pain control, mood

22
Q

acetyle choline system

A

gigantocellular neurones in REA forms discrete synapses, but also indiscrete synapses where can secrete acetyl choline
usually excitatory
causes acutely awake + excited nervous system, drives REM sleep

23
Q

acetyle choline system drives

A

REM sleep

24
Q

acetyl choline system is off during

A

non-REM sleep

25
Q

glutamate

A

most abundant excitatory NT in CNS
binds NMDA or AMPA receptors
a GABA precursor (requires glutamate decarboxylase)

26
Q

GABA

A 
cheif inhibitory NT in CNS
binds GABAa (Cl- channels) or GABAb (GPCR > K+ channel) receptors
27
Q

what excites the excitatory area

A

peripheral sensory signals and feedback

28
Q

peripheral sensory signals activatng excitatory area

A

cut brain stem mid pons (above CN V) - coma unlikely

pain signals strongly excite the brains attention

29
Q

feedback exciting the excitatory system

A 
cortex activation (motor/thought) > REA > cortex activation (thalamic feedback also) 
any cerebral activity > awake mind
30
Q

3 functional brain imaging techniques

A

electroenencephalography EEG
positron emission tomography PET
functional magnetic resonance imaging

31
Q

spatial resolution

A

how accurately is location determined
worst - EEG
best - PET

32
Q

temporal resoltuion

A

accuracy of determining timing of activity (ms)
terrible - PET
pretty bad - fMRI
excellent - EEG

33
Q

Electroencephalography

A

old technique, still used
- brain wave activity, rather than for imaging
any neuronal activity > electric current flow
current flows through cranium and scalp
changes in electric potential are detected by electrodes paced on the scalp

34
Q

clinical utility of the EEG

A

changes in electrical activity are evident in states such as sleep, wakefulness and arousal

35
Q

EEG is useful for diagnosis of

A 
epilepsy/seizures 
sleep abnormalities 
coma 
confirmation of brain death-flat EEG 
psychiatric disorders - gamma rhythm
36
Q

detecting electrical activity

A

when excited - no need for excitatory effect - low brain activity detected
when relaxed - significant brain activity needed to keep brain awake

37
Q

coma

A

widespread cortical damage - consciouness requires functioning cortex
damage to ascending reticular activating systems causes permanent sleep - coma

38
Q

seizures

A

breif episodes of abnormal excessive or synchronous neuronal activity in the brain
effects vary - momentary loss of awareness - absense sezure
uncontrolled jerking movemnt - tonic-clonic seizure

39
Q

positron emission tomography

A

measures distribution of organic molecules/compounds - water, glucose, neurotransmitters
tracer injected IV
flow to areas with highest metabolic needs
shows areas of different hues representing different areas of activation

40
Q

tracers used for PET

A

positron emitting isotopes of organic molecules/compounds

such as flouridated glucose 18F-FDG

41
Q

tracer PET image superimposed onto

A

MRI or CT scan

42
Q

resolution of PET

A

spatial - 5-10 mm

temporal - minutes

43
Q

functional magnetic resonance imaging fMRI

A

measures oxygenated blood
if neurones increase firing they increase metablolic rate and need more bloood flow
bad temporal resolution
good spacial resolution

44
Q

why does fMRI have bad temporal resolution

A

image reflect blood flow 5 to 8 seconds after neurons fire

physiology 3 (7 decks)

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