Adrenergic system Flashcards
How is noradrenaline synthesized?
- Phenylalanine is hydroxylated into tyrosine.
- Tyrosine is hydroxylated into DOPA.
- DOPA is decarboxylated into Dopamine.
- Dopamine is hydroxylated into noradrenaline.
Where is noradrenaline synthesized in the neuron pathway?
Pre-ganglionic neurone
Which receptor causes vesicles to stop releasing noradrenaline once binded to?
alpha 2 receptor
Which transporter transports noradrenaline into non-neuronal effector cells?
Extraneuronal monoamine transporter (EMT)
How much of noradrenaline is uptaken by non-neuronal cells?
25%
What metabolises noradrenaline?
monoamine oxidase and catechol-O-methyl transferase
MAO is found on the surface membrane of mitochondria [intracellular
How much noradrenaline is re-packaged into vesicles?
75%
G-protein cycle
ACTIVATION-DEACTIVATION
- G-protein binds to GPRC
- GDP on a-subunit is exchanged for a GTP [ACTIVATES]
- α-subunit acts as a GTPase and breakdowns GTP to GDP to DE-ACTIVATE the protein.
GEFs
Guanine nucleotide Exchange Factor
They speed up the activation of G-protein.
GAPs
GTPase-activating protein
They accelerate the hydrolysis of the GTP to GDP to DE-ACTIVATE the G-protein.
GAi
An α-subunit that inhibits adenyl cyclase - decreases cAMP
GAs
A stimulatory α-subunit that ACTIVATES adenylate cyclase
G_βγ
An effector subunit that binds to and activates other proteins
IMPORTANT EXAMPLE: Phospholipase C
MAO
Monoamine oxidase
COMT
Catechol O-methyl transferase
β2 adrenoreceptor agonist
Relax the smooth muscle in the airway.
Used as bronchodilators in medicine.
α2 adrenoreceptor
Inhibits vesicle release of noredrenaline.
Activates the Gi protein that inhibits adenyl cyclase and therefore REDUCES levels of cAMP. This is turn results in lower PKA which inactivates the Calcium channels.
β adrenoreceptor
Noradrenaline binding stimulates adenylate cyclase. This increase cAMP levels and activates protein kinase A.
Result: calcium channels and plasma membrane open.
