regulation of cortical excitability

Question 1

no cortical excitation

Answer 1

coma

Question 2

cerebullum needs

Answer 2

constant activation by lower centres

Question 3

brainstem compression creates

Answer 3

coma

Question 4

2 forms of cortical stimulation

Answer 4

direct neuronal stimulation

neurohormonal systems

Question 5

reticular formation

Answer 5

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

Question 6

reticular excitatory area

Answer 6

sits below the reticular formation

goes through the thalamus and into every region of the cortex

Question 7

reticular inhibitory area

Answer 7

turns out the reticular excitatory area

Question 8

what feeds into excitatory area

Answer 8

sensory information from the rest of the body

Question 9

what is the REA - reticular exctatory system - for

Answer 9

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

Question 10

why does the REA send signals downward

Answer 10

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

Question 11

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

Answer 11

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

Question 12

rapid transmission to excite cerebrum

Answer 12

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

Question 13

nuerohormonal transmission

Answer 13

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

Question 14

reticular inhibitory area is located in

Answer 14

medulla in reticular formation

Question 15

reticular inhibitory area inhibits

Answer 15

excitation of the REA via serotonergic projections

5-HT is inhibitory - supresses using serotonin

Question 16

4 types of neurohormonal control

Answer 16

noradrenaline system
dopamine system
serptonin syetm
acetylcholine system

Question 17

noradrenaline system

Answer 17

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

Question 18

noradrenaline system s inactive during

Answer 18

REM sleep

Question 19

noradrenaline system is active during

Answer 19

wakefullness and non REM sleep

Question 20

dopamine system

Answer 20

excitatory or inhibitory (region dependant)

fibres innervate specific region

Question 21

serotonin system

Answer 21

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

Question 22

acetyle choline system

Answer 22

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

Question 23

acetyle choline system drives

Answer 23

REM sleep

Question 24

acetyl choline system is off during

Answer 24

non-REM sleep

Question 25

glutamate

Answer 25

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

Question 26

GABA

Answer 26

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

Question 27

what excites the excitatory area

Answer 27

peripheral sensory signals and feedback

Question 28

peripheral sensory signals activatng excitatory area

Answer 28

cut brain stem mid pons (above CN V) - coma unlikely | pain signals strongly excite the brains attention

Question 29

feedback exciting the excitatory system

Answer 29

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

Question 30

3 functional brain imaging techniques

Answer 30

electroenencephalography EEG positron emission tomography PET functional magnetic resonance imaging

Question 31

spatial resolution

Answer 31

how accurately is location determined worst - EEG best - PET

Question 32

temporal resoltuion

Answer 32

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

Question 33

Electroencephalography

Answer 33

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

Question 34

clinical utility of the EEG

Answer 34

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

Question 35

EEG is useful for diagnosis of

Answer 35

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

Question 36

detecting electrical activity

Answer 36

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

Question 37

coma

Answer 37

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

Question 38

seizures

Answer 38

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

Question 39

positron emission tomography

Answer 39

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

Question 40

tracers used for PET

Answer 40

positron emitting isotopes of organic molecules/compounds | such as flouridated glucose 18F-FDG

Question 41

tracer PET image superimposed onto

Answer 41

MRI or CT scan

Question 42

resolution of PET

Answer 42

spatial - 5-10 mm | temporal - minutes

Question 43

functional magnetic resonance imaging fMRI

Answer 43

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

Question 44

why does fMRI have bad temporal resolution

Answer 44

image reflect blood flow 5 to 8 seconds after neurons fire