L10: Drugs affecting SYM NS 1 Flashcards
(29 cards)
3 branches in the peripheral nervous system
1) Somatic NS
2) Autonomic NS
3) Enteric NS
What does sympathetic NS prepare us for?
Flight or fight
How does efferent nerves of the sympathetic NS leave?
Spinal cord in the thoracic & lumbar regions
Role of adrenal medulla
Controls hormones that initiates fight or flight responses
Main hormones secreted by the adrenal medulla
1) Epinephrine (Adrenaline)
2) Norepinephrine (Noradrenaline)
What acts as neurotransmitters in the sympathetic NS?
ACh & noradrenaline
What do post-ganglionic nerves in the SNS release?
Noradrenaline as their neurotransmitter = noradrenergic nerves
Features of the postganglionic nerves
Varicosities: ‘swellings’ along their length wich releases noradrenaline
Steps of the synthesis of NA
1) Tyrosine converted to DOPA by tyrosine hydroxylase
2) DOPA converted to dopamine by DOPA decarboxylase
3) Dopamine converted to NA by Dopamine b-hydroxylase
What happens after the synthesis of dopamine to NA that synthesises adrenaline?
Chromaffin cells of adrenal medulla contains PNMT which converts NA into adrenaline
Role of the drug carbidopa
Inhibits the enzyme DOPA decarboxylase
Role of drug a-methyl tyrosine
Inhibits tyrosine hydroxylase which secretes a lot of adrenaline
Release of noradrenaline
How is exocytosis triggered?
Increase in intracellular conc of Ca2+ ions caused by Ca2+ entering the channels, opened by an AP
Release of noradrenaline 2
How does the released noradrenaline act?
Act on receptors found on target tissue but some act on a2-adrenoreceptors found on varicosity
How can release of noradrenaline be inhibited?
“Noradrenergic neurone blocking” drug guanethidine
How do noradrenaline & adrenaline produce their effects by doing?
Activating “adrenoceptors”
Define adrenoceptors
A group of nine 7-transmembrane receptors comprising of 3 main types: a1, a2, and a3
Which 4 main types of adrenoceptor is used to explain drug action?
a1, a2, b1, b2
All GPCRs (G-protein coupled receptors)
Removal of noradrenaline
1st step of removal
2nd step: What happens to the remaining 25% of noradrenaline?
Once released, about 75% of noradrenaline is removed from synapse & taken back into the varicosity by Uptake-1 carried out by the norepinephrine transporter (NET)
Taken up into other cells by Uptake-2 carried out by extraneuronal monoamine transporter (EMT)
What 2 things can happen to the noradrenaline when it is inside the varicosity?
1) Taken back up into the synaptic vesicles by VMAT
2) Destoryed by enzyme Monoamine Oxidase (MAO)
What does NET stand for?
Norepinephrine transporter
Role of norepinephrine transporter (NET)
Remove neurotransmitters from synapses
1 drug that inhibits NET
Cocainel; increase extracellular concentration of noradrnealine in both peripheral & CNS
How can recycled noradrenaline be can increased further?
By **monoamine oxidase ** which repackages them into vesicles
