18. The Autonomic Nervous System Flashcards
What are the 12 main steps in neurotransmission?
- Uptake of precursors. 2. Synthesis of transmitter. 3. Vesicular storage of transmitter. 4. Degradation of transmitter. 5. Depolarisation by propagated action potential. 6. Depolarisation-dependent influx of Ca2+. 7. Exocytotic release of transmitter. 8. Diffusion to post-synaptic membrane. 9. Interaction with post-synaptic receptors. 10. Inactivation of transmitter. 11. Re-uptake of transmitter. 12. Interaction with pre-synaptic receptors.
Which steps in neurotransmission are targeted pharmacologically?
Degradation of transmitter, interaction with post-synaptic receptors, inactivation of transmitter, re-uptake of transmitter, interaction with pre-synaptic receptor.
Which enzyme catalyses synthesis of acetylcholine?
Choline acetyltransferase.
Which enzyme catalyses degradation of acetylcholine?
Acetylincholinesterase.
How do drugs have selectivity at autonomic ganglia over nicotinic acetylcholine receptors at the neuromuscular junction?
The structures are different so drugs may only bind to one.
How many types of muscarinic acetylcholine receptors are there?
5: M1-M5.
How can the actions of endogenously released ACh be enhanced?
By AChE inhibitors as ACh is broken down slower so is the neuromuscular junction for longer to act longer.
What limits the useage of cholinergic drugs?
The lack of selectivity, as it means there are unwanted side-effects.
What is SLUDGE?
A mnemonic for the pathological effects indicative of massive discharge of the parasympathetic nervous system.
What are the symptoms in SLUDGE due to?
Chronic stimulation of muscarinic acetylcholine receptors in organs and muscles innervated by the parasympathetic nervous system.
What are the symptoms in SLUDGE?
Salivation, Lacrimation, Urination, Defecation, Gastrointestinal upset, Emesis (vomiting).
How can SLUDGE be treated?
With atropine, pralidoxime, or other anticholinergic agents.
What are some muscarinic ACh receptor agonists and their functions?
Pilocarpine - treats glaucoma. Bethanechol - stimulate bladder emptying.
What are some muscarinic ACh receptor antagonists and their functions?
Ipratropium and tiotropium - some types of asthma and COPD. Tolterodine, darifenacin, and oxybutynin - overactive bladder treatment.
How is noradrenaline synthesised?
In the cytosol: Tyrosine -> DOPA (tyrosine hydroxylase). DOPA -> Dopamine (DOPA decaroxylase). In the vesicle: Dopamine -> Noradrenaline (Dopamine B-hydroxylase).
