Module B Flashcards
Provocholine (Methacoline)
- Direct-acting cholinergic with greater M3 muscarinic specificity
- Broad systemic effects, but mainly respiratory (SLUDGE), decreased heart rate, increased PR, decreased gastric secretions and GI motility
- Used in the methacholine challenge test (MCT) for asthma. Small doses of methacholine may induce bronchospasm and excessive mucus production in those with reactive airways
Branches of the sympathetic nervous system arise from:
T1 through L3
Sympathetic nerves have ________ pre-ganglionic neurons and ________ post-ganglionic neurons
short, long
Black Widow spider venom exerts its toxic effects by _________ (stimulating / inhibiting) release of _________
stimulating, acetylcholine
M3 muscarinic receptors, belong to the class ________ and are found in ________
they are Gαq GPCRs (therefor stimulute phospholipase C activity and increase IP3 and DAG contentrations) and are found in smooth muscle, glands, and vascular smooth muscle
The GI and GU effects of muscarinic activation are:
- Increased salivary, gastric, and other secretions
- Increased smooth muscle contraction (except sphincters) leading to increased GI motility
- Micturition due to detrussor stimulation and internal urethral sphincter relaxation
Overdose may lead to “all faucets turned on” syndrome of excessive salivation, diarrhea, incontinence.
Name, compare and contrast the two common kinds of indirect-acting cholinergic drugs:
The two types are reversible and quasireversible cholinesterase inhibitors. Both inhibit the function of acetylcholinesterase and thereby functionally increase the concentration of ACh in the synapse.
Reversible cholinesterase inhibitors (Edrophonium, neostigmine) are slowly hydrolyzed by AChase, and are rapidly excreted, leading to a short duration of action
Quasireversible cholinesterase inhibitors act in a similar way but form a covalent bond with AChase and take much longer to be hydrolyzed (ex: isofluorophate). These are common causes of organophosphate poisoning.
Three reasons the sympathetic nervous system tends to have broad, systemic effects when activated are:
- The sympathetic nervous system tends to discharge as a unit
- Each sympathetic preganglionic neuron innervates many post-ganglionic neurons
- Sympathetic activation triggers release of epinephrine and norepinephrine into the systemic circulation
Branches of the parasympathetic nervous system arise from:
CN III, VII, IX, and X, and S2-S4
the ENS _____ (can / can not) function independently of the CNS after autonomic denervation
can!
All somatic motor neurons use ________ as a neurotransmitter at the neuromuscular junction
All somatic motor neurons use acetylcholine as a neurotransmitter at the neuromuscular junction
Nicotinic receptors belong to the receptor class _________
ligand-gated sodium channels
parasympathetic pre-ganglionic neurons synapse with ________ (many / few) post-ganglionic neurons and therefore produce ________ (broad / specific) effects.
parasympathetic pre-ganglionic neurons synapse with few post-ganglionic neurons and therefore produce specific effects.
Tensilon (Edrophonium)
- Short-acting reversible cholinesterase inhibitor (indirect-acting cholinnergic)
- rapidly increases ACh concentrations
- may be used to reverse neuromuscular blockade
- used to diagnose between myasthenic crisis (not enough ACh) and a cholinergic crisis (too much ACh) in myasthenia gravis
Botulinum toxin A ________ (stimulates / inhibits) the release of ________ which results in ________
Botulinum toxin A inhibits the release of acetylcholine which results in decreased neuromuscular transmission
This is used to treat disorders of innapropriate muscle tone/activation as in parkinsons, CP, bladder spasm, strabismus, etc.
Paraympathetic nerves have ________ pre-ganglionic neurons and ________ post-ganglionic neurons
long, short
Prostigmin (Neostigmine)
- Reversible cholinesterase inhibitor (indirect-acting cholinergics)
- Relatively long-acting (compared to edrophonium)
- Used in long-term treatment of myasthenia gravis and in reversal of NMBA blockade
The bronchial effects of muscarinic activation are:
bronchoconstriction, hypersecretion of mucus
Describe the general process of acetylcholine synthesis, storage, and release
- Synthesized from choline and acetate by choline acetyltransferase
- Stored in presynaptic vesicles
- Action potential triggers vesicle fusion with presynaptic membrane
- ACh released across synapse to bind with post-synaptic receptors
- ACh hydrolyzed acetylcholinesterase back to acetate and choline
- Choline is recycled through presynaptic reuptake
The ocular effects of M3 muscarinic receptor activation are:
miosis (pupillary constriction), accomodation (ciliary muscle contraction for near vision), and lacrimation
______________ is similar to acetylcholinesterase but is found in blood plasma and is important in breakdown of cholinergic drugs
pseudocholinesterase
Expain why direct cholinergic agonists have limited clinical use.
it is difficult to produce specificity in thse drugs for particular nicotinic or muscarinic receptors, so the rate of adverse reaction is very high (low TI and CSF)
The effect of stimulating M3 muscarinic receptors in non-vascular smooth muscle is
increased calcium release and muscle contraction
The effect of stimulating M2 muscarinic receptors is
decreases cAMP production in cardiomyocytes, slowing heart rate and conduction
Describe the difference between direct-acting and indirect-acting cholinergics
direct-acting cholinergics directly stimulate an ACh recptor (ex: Provocholine (Methacholine))
indirect-acting cholinergics increase the concentration of ACh or augment ACh signal transduction in some way (ex: Tensilon (Edrophonium)) prominent examples are acetylcholinesterase inhibitors
the enteric nervous system (ENS) is innervated by the ________ (sympathetic / parasympathetic / both) branch of the ANS
both sympathetic and parasympathetic
The cardiac effects of muscarinic activation are:
Decrease SA diastolic depolariztion (slows heart rate), Slow AV nodal conduction (prolonged P-R interval)
sympathetic pre-ganglionic neurons synapse with ________ (many / few) post-ganglionic neurons and therefore produce ________ (broad / specific) effects.
sympathetic pre-ganglionic neurons synapse with many post-ganglionic neurons and therefore produce broad effects.
The vascular effects of muscarinic activation are
vasodilation due to nitrous oxide release, stimulated by increased IP3 and DAG levels.
muscarinic receptors belong to the receptor class _________
G-protein coupled receptors (GPCRs)
List three uses of reversible cholinesterase inhibitors (indirect-acting cholinergics)
- reversal of neuromuscular blockade by curariform drugs
- Diagnose/treat disorders of ACh (ex: edrophonium for myasthenia gravis)
- Treat glaucoma (ex: pilocarpine)
The two types of nicotinic receptors are:
neuronal type (nN) and muscle type (mN)
The two types of acetylcholine receptors are:
nicotinic and muscarinic
Nicotinic receptors are found at: (list 3)
all autonomic ganglia, neuromusuclar junctions, and in the CNS
The effect of stimulating M3 muscarinic receptors in vascular smooth muscle is:
nitric oxide synthesis and smooth muscle relaxation
The neurotransmitter released at sympathetic preganglionic synapses and at all parasympathetic synapses is _________
acetylcholine
Muscarinic receptors are found at: (list 3)
smooth muscle, cardiac tissue, and glands innervated by the parasympathetic nervous system. They are also found at some sympathetic neuroeffector junctions, specifically sweat glands and chromaffin cells.
Muscarinic receptors may also be found on sympathetic terminals where the PNS exerts an inhibitory effect on norepinephrine release
The effect of stimulating M3 muscarinic receptors in glands is
increased glandular secretion
The purpose of ACh autoreceptors is:
to provide negative feedback at cholinergic synapses
M2 muscarinic receptors, belong to the class ________ and are found in ________
they are Gαi GPCRs (therefor inihibit adenylyl cyclase activity) and are found in cardiac muscle tissue.
Viagra (sildenafil)
- Type 5 phosphodiesterase inhibitor (PDE5 inhibitor)
- PNS innervation of vascular smooth muscle causes vasodilation and cGMP release (causing further smooth muscle relaxation). PDE5 inhibitors slow the breakdown of cGMP leading to increased/prolonged vasodilation.
- As Viagra, sildenafil is used to treat erectile dysfunction
What are the three primary clinical uses of muscarinic receptor antagonists?
- relax smooth muscle (vasodilation)
- reduce glandular secretions
- increase heart rate