NT of the brain Flashcards
GABA
main INHBITORY NT in the brain (trace amounts in other tissue)
Glycine
main INHIBTORY NT in the brainstem and spinal cord
Glutmate
main EXCITATORY NT in the body
two types of GABA which different receptors
GABAa
GABAb
GABAa receptor
ligand gated chloride channels- hyperpolarization- reduces excitability
- allowing influx of cl- ins- taking the neurone further from its threshold potential
GABAb
signals via Gi/Go
- inhibiting VOCCs and opens K+ channels= reducing excitability
GABA is synthesised from
glutamate
GABAergic neurones represent the sole output of the
cerebellar codex and plays a major role in basal ganglia pathways
glycine have a similar mode of action to
GABAa
- opening ligand gated chloride channels- hyperpolarization
both GABA and glycine are
used by many interneurones including those involved in regulation of muscle tone
describe Gi/Go
1) ligand binds and beta/gamma complex dissociates
2) Gi protein inhibits adnelyl cycle
3) less cAMP produced
4) less pKA
Go part
1) excited GIRKs (gated INWARDLY rectifying potassium ) channel
2) causing influx of K+
3) hyperpolarisation
Two types of receptors for glutamate
Ionotropic- ligand gated cations
Metabotropic- mGlu
Glutamate inotropic receptors
NMDA
AMPA
Kainate
NMDA glutamate receptors
calcium
- Magnesium block, therefore certain level of depolarisation needed
AMPA and kainate glutamate receptors
Na+
Metabotropic glutamte receptors
metabotropicGlu GPCR
- signal via Gaq
mGlu and Gaq
1) glutamate binds
2) causes gabba/beta to dislocate from Gq
3) triggers PLC to hydrolyse IP3 to PIP2 and DAG
4) DAG- PKC
5) IP3- SR calcium release
Glutamate and NMDA
NMDA has large proc so will allow larger cations through- has Mg2+ bock, will only be removed at certain potential
Glutamate and AMPA and kainate
smaller pores so will only let Na thoguh- FAST
catecholamines include
adrenaline
noradrenaline
dopamine
what is the main precursor of catecholamines
tyrosine kinase
where are noradrenaline and adrenal released from
adrenal medulla
pathway of making catecholamines
1) phenylalanine - essential AA
2) tyrosine
3) DOPA
4) dopamine
5) noradrenaline
6) adrenaline
dopamine
released in the brain to coordinate movement
- corpus striatum
- precursor is L-DOPA
which enzyme converts L-DOPA
DOPAdecarboxylase
Noradrenlaine
mostly release in the brainstem
-locus coerulues
0 mainly found in the brain where adrenergic neurones are found
-involved in behaviour arousal for threat or unfamiliar situations
noradrenaline is stimulatory for
heart regulation (B1) vasodilation in the lungs (B2)
dopaminergic synapse
1) tyrosine diffuses into neurone
2) converted to DOPA
3) converted to Dopamine and stored in synaptic vesicle
4) impulse cause calcium to flood in and causes SNARE proteins to transport the vesicles the synapse
5) release int cleft and stimulate D1R and D2R
6) dopamine is recycled back tot he presynaptic membrane by dopamine transporter
7) converted to DOPAC by MAO
adrenaline
Also known as epinephrine
Hormone, NT and medication
Produced by adrenal glands and certain neurones
Play an imporntant role in fight or flight repsosne by increasing blood flow to muscle, output of the hear, pupil dilation and blood sugar
Does this by binding to alpha and beta receptors
serotonin
5-HT
- monamine NT
- contirbutor to feelings of well-being and happiness
- treamtent for depression
serotonin strongly influences
the transmission of other NT, including dopamine and noradrenaline- reciprocal relationship
D1R
direct- stimulatory
D2R
indirect- inhibitory
two pathways of Dopamine which control movement
- direct- stimulates cortex for movement
- indirect- inhibits context to stop movement
Direct dopaminergic pathway
inhibitory neurone connecting the basal ganglia and thalamus are inactivated- therefore the thalamus can send excitatory input to motor cortex and movement can occur
Indirect dopaminergic pathway
inhibiting neurones are activated. so movement is prevented
why is the indirect pathway important
- allows us to stay at rest
- when we want to move the indirect pathway is tuned off and the direct pathway is turned on
dopamine related forms the substantial nigra cells will
both activate and inactivate direct pathway
Direct pathway detail
- Cortex provides excitatory input to the striatum
- The striatum then puts an inhibitory output to the GPI and SNR
- Therefore inhibition the inhibitory neurones leading to the to the thalamus
- This means the thalamus can send excitatory input to the cortex
Overall effect is to stimulate the cortex
indirect pathways
- Cortex provides excitatory input to the striatum
- However, striatum then provides inhibitory input to the GPE
- GPE, therefore sends inhibitory input to SNP- inhibits the thalamus
- Preventing the thalamus from sending excitatory input to the cortex
Longer and less direct.
