Drugs And Parasympatheitc NS SEM2 Flashcards
What is muscarine
A direct-acting acetylcholine receptor agonist
What can nicotinic receptors which are ligand gated ion channels be classified into
Skeletal NMJ
Ganglionic
Neuronal CNS
What system do muscarinic Ach receptors work with
The parasympathetic nervous system (and CNS)
Where does the pre-ganglion neuron start from and what does it release
Starts from the spinal cord and releases ACh which activates nicotinic acetylcholine receptors on the parasympathetic ganglion
What is activated following the signal relayed to another neurone in the parasympathetic ganglion
ACh released again and activates muscarinic ACh receptors on an effector organ (glands or smooth muscle)
Where does the pre-ganglionic neurone originate from and what does it release
Originates at the spinal cord and releases ACh to activate nicotinic ACh receptors in the sympathetic chain ganglion
What occurs after ACh receptors in the sympathetic chain ganglion have been acivated
Signal transmitted to another neurone that releases norepinephrine (NA) activating adrenoceptors on target effector organ => fight or flight
What can muscarinic receptors activate
Activate phospholipase C leading to the production of IP3 and diacyle glycerol - M1, M2, M3
Activate K+ channels - M2
What can muscarinic receptors inhibit
Inhibit adenylate cyclase causing a decrease in the levels of cAMP - M2, M4
Inhibit Ca2+ channels - M2
What do the terms parasympathomimetic and cholinomimetic mean
Drugs that mimic the effects of the parasympathetic nervous system
What are properties of direct acting drugs of cholinomimetic drugs
Mainly have muscarinic effects at end effectors
Most do not have CNS effects
What are properties of indirect acting drugs of cholinomimetic drugs
Increase transmission at all cholinergic junctions therefor have muscarinic, ganglionic and skeletal muscle effects
Have CNS effects
What are properties of indirect reversible acting agonist
Reversible inhibitors of ACh-esterase can increase the concentration of ACh and prolong lifetime in the synapse/junction
What are properties of indirect irreversible acting agonists
Irreversible inhibitors of ACh-esterase increase concentration of ACh and prolong lifetime in the synapse/junction
What are examples of reversible inhibitors of ACh-esterase
Physostigmine
Neostigmine
What are examples of irreversible inhibitors of ACh-esterase
Organophosphates
What are the therapeutic uses of antimuscarinics
Pre-anaesthetic medication
Ophthalmological uses
Gastrointestinal antispasmodic agents
Treatment of poisoning by cholinomimetics
What are types of sympathetic neurotransmitters
Noradrenaline
Adrenaline
What occurs when noradrenaline (NA) travels to thee effector organ
NA interacts with adrenoceptors on the effector organ, initiating response typically being:
increasing heart rate
Dilating airways
Mobilising energy stores
What occurs during the process of neuronal uptake 1 of noradrenalin re uptake
The majority of NA is taken back into the pre-synaptic neurone via a high affinity uptake system known as uptake 1
What occurs during the process of extra-neuronal uptake 2 of noradrenalin re uptake
NA that escapes uptake 1 can be bysorbed by non-neuronal cells e.g glial cells
Has lower affinity for NA but maximum rate meaning it can handle larger amounts of NA, adrenaline and isoprenaline
What occurs during the process of the metabolism of noradrenaline (NA)
Monoamine oxidase (MAO) breaks down NA into aldehydes which are further metabolised to acids or non-active forms which can be excreted
What is the cellular response of alpha-1 (α1) adrenoceptors
IP3 induces the release of calcium ions from intracellular stores leading to the contraction of smooth muscle
What is the cellular response of alpha-2 (α2) adrenoceptors
The reduced cAMP levels lead to inhibition of transmitter release
What is the cellular response of beta ( β 1-3) adrenoceptors
β1: increases heart muscle contraction
β2 + β3: relaxation of smooth muscle and glycogenolysis
What does guanethidine do when accumilates in veiscles
Displaces noradrenaline (NA)
What is the result of guanethidine accumilating in the vesicle and displacing NA
Displacement of NA leads to guanethidine preventing the release of NA into the synaptic cleft therefor reduces the amount of NA available to activate adrenergic receptors
