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Cholinergic Pharm1
Qs and As about Cholinergic Pharmacology
| Question | Answer |
|---|---|
| Choline acetyltransferase (ChAT) = | Enzyme involved in resynthesis of ACh from acetyl coA and choline |
| M2 receptors are primarily located in which tissue(s)? | Heart, Presynaptic terminals?? |
| M3 receptors are primarily located in which tissue(s)? | Bronchi, Vasculature, Pupils, Bladder, Smooth muscle, glands |
| Muscarinic receptors are activated by ACh release from the SNS in only one tissue: | Sweat glands |
| The SNS releases which neurotransmitter at sweat glands? | ACh |
| Nicotinic receptors transduce signals via: | Ion channels |
| Muscarinic receptors transduce signals via: | G-protein coupled receptors |
| Number of bound ACh molecules needed to activate nicotinic receptors = | 2 |
| Number of bound ACh molecules needed to activate muscarinic receptors = | 1 |
| The rate-limiting step of ACh synthesis is: | Uptake of choline into the presynaptic neuron |
| M3 receptors lead to (excitatory/inhibitory) activity through their effects on ______. | excitatory; PLC --> IP3 --> increase intracellular Ca2+ |
| M2 receptors lead to (excitatory/inhibitory) activity through their effects on ______. | inhibitory; K+ channels (open --> hyperpolarization), also decr inward Ca2+ current, inhibit adenylyl cyclase |
| Nm receptors lead to (excitatory/inhibitory) activity through their effects on ______. | excitatory; Na+/K+ channels |
| Acetylcholinesterase (AChE) | Hydrolyzes ACh to inactive fragments (choline + acetate) |
| ACh hydrolysis is (faster/slower/the same) at the NMJ compared to ganglionic synapses. | The same |
| ACh hydrolysis is (faster/slower/the same) at the NMJ compared to the postganglionic neuroeffector junction of muscarinic receptors. | Faster |
| The effects of ACh are (longer/shorter) lasting at muscarinic neuroeffector junctions compared to nicotinic NMJs. | Longer |
| Nicotinic Nm receptors are primarily located in which tissue(s)? | NMJ of skeletal muscle |
| Nicotinic Nn receptors are primarily located in which tissue(s)? | ANS ganglia, adrenal medulla |
| Why do Nm and Nn receptors respond differently to nicotinic drugs? | The alpha subunit, where ACh binds, is different in Nm and Nn receptors. |
| Supra-sensitivity to cholinergic agents | System damage (burn trauma, cut nerve) causes nicotinic receptors to spread over entire sarcolemma instead of being confined to endplate |
| Desensitization of nicotinic receptor | Prolonged exposure to nicotinic agonists leads to a lower change in membrane potential |
| Hyperkalemia | Dispersed nicotinic receptors from trauma -- depolarization (e.g. with succinylcholine) can lead to dangerously high extracellular K+ (can shut down heart) |
| Safety factor | At motor nerve: much higher end plate potential (EPP) than what is needed to trigger an AP in muscle |
| There is a (higher, lower) safety factor at ganglionic synapses than at neuromuscular synapses. | Lower |
| Number of synaptic potentials generated at the NMJ | 1 |
| Number of synaptic potentials generated at autonomic ganglia | 4+ |
| The only synaptic potential generated by nicotinic receptors is: | fast EPSP |
| The fast EPSP | triggers the postsynaptic AP |
| The slow IPSP, slow EPSP, and late, slow EPSP | modulate the excitability of ganglionic cells |
| Activation of M2 receptors leads to | bradycardia, decr AV conduction, negative inotropic effect |
| Muscarinic effects are elicited by (higher/lower/same) concentrations of ACh compared to nicotinic effects | Lower |
| 3 major effects of increased doses of atropine (in order): | increased salivation; increased HR; decreased GI motility |
| Two types of cholinesterases in the body | Acetylcholinesterase (AChE), Butyrylcholinesterase (BChE) |
| Distribution of AChE in the body | bound to basement membrane of synaptic cleft of cholinergic synapses; RBC membranes |
| Distribution of BChE in the body | liver, brain, plasma |
| Selectivity of AChE: | Relatively selective for ACh, does not metabolize ester type drugs |
| ACh is positioned on AChE via (type of interaction) to the (esteratic/anionic) site | electrostatic attraction; anionic site |
| ACh is bound to AChE via (type of interaction) to the (esteratic/anionic) site | covalent bonding; esteratic site |
| Selectivity of BChE: | Relatively nonselective, metabolizes some other choline esters more rapidly than ACh, also metabolizes ester containing drugs like procaine + succinylcholine |
| Early symptoms of AChE toxicity: | Runny nose, bronchial secretions, chest tightness, vision trouble/pain, pin-point pupils, drooling, sweating, nausea/vomiting, defecation, seizure, coma, death |
| Two conditions with contraindications to atropine | Glaucoma, prostatic hypertrophy |
| ACh increases EDNF/NO, which leads to... | dilation of arterioles and decreased BP |
| Malignant hyperthermia | inherited inability of sarcoplasmic reticulum to sequester Ca2+; abnormal Ca2+ release can lead to prolonged m. contractions, lactic a. production, increased body temp |
| How might malignant hyperthermia be triggered iatrogenically? | Administration of succinylcholine w/volatile anesthetics in a patient with rare heritable impairment in ability to sequester Ca2+ |
| Malignant hyperthermia is treatable with... | Dantrolene (blocks opening of ryanodine receptor channels in skeletal m.) |
| 3 situations in which succinylcholine can induce contractures | diabetic neuropathy, general myopathies/injuries with denervation sensitivity, malignant hyperthermia |
| Tetanic fade in train of 4 monitoring is seen in which type of NM block? | Nondepolarizing NM block |
| Constant but diminished train of 4 monitoring is seen in which type of NM block? | Depolarizing block (phase I) |
| A myasthenic patient will be (more/less) sensitive to nondepolarizing blockers? | More |
| A myasthenic patient will be (more/less) sensitive to depolarizing blockers? | Less |
Created by:
eemolee27
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