ANS Flashcards
What are the receptor types in the parasympathetic division?
Muscarinic (M2, M3, and M) and Nicotinic (Nn and Nm)
Where can M2 receptors be found? Cholinergic nerve response at each site?
SA node- decrease HR, AV node- decrease conduction velocity, Atria and Ventricles- decrease contractility
Where can M3 receptors be found and the cholinergic nerve response at each location?
VSM- constriction, Endothelium- NO, dilation, Bronchial muscles- constriction, Bronchial glands- secretion, GI- increase motility/tone, relax sphincters, and increase proton pump secretion, Detrusor- contraction, Trigone & sphincter- relaxation, Penis- erection, Eye sphincter- contraction (miosis), Ciliary muscle- contract (focus near), and Salivary glands- salivation
Where can the M receptor be found? cholinergic nerve response?
sweat glands, sympathetic response, perspiration
Where can Nn receptors be found? Cholinergic nerve stimulation response?
autonomic ganglia, EPSP
Where can Nm2 receptors be found? Cholinergic nerve stimulation response? What part of nervous system?
skeletal muscle contraction, somatic system
what are the sympathetic system receptors?
M, Nn, Nn2, B1, B2, B3, A1, A2
Where can M receptors be found? What is their cholinergic nerve response?
sweat glands, perspiration, sympathetic
Where can Nn2 receptors be found? Cholinergic nerve stimulation?
adrenal medulla, epinephrine release
Where can B1 receptors be found? What is the response to adrenergic nerve stimulation?
SA node- increased HR, AV node- increased conduction velocity, atria and ventricles- increased contractility, Kidney- increased renin release
Where can B2 receptors be found? What is the response to adrenergic nerve stimulation?
skeletal muscle BV- dilation, bronchial muscle- dilation, detrusor- relaxation, ciliary muscle- relax (focus far), uterus- relaxation, liver- glycogenolysis
Where can B3 receptors be found? What is the response to adrenergic nerve stimulation?
detrusor muscle- relaxation
Where can A1 receptors be found? What is the response to adrenergic nerve stimulation?
BV- constriction, Trigone & sphincter- contraction, penis- ejaculation, radial muscle- constriction (mydriasis), uterus- contraction
Where can A2 receptors be found? What is the response to adrenergic nerve stimulation?
adrenergic neurons- decreased transmitter release (- feedback)
What action on what receptor does mecamylamine have?
non-competitive antagonist of Nn, blocks PNS and SNS postganglionic, reveals dominant ANS controlling the tissue
What are the tissue responses seen with mecamylamine? which tissues are SNS dominant? PNS dominant?
arterioles-dilate (S), veins- dilate (pooling, S), heart tachycardia(PS), iris- mydriasis (PS), ciliary- cycloplegia (blurred vision, PS), GI- constipation (PS), Bladder- urine retention (PS), salivary glands- dry mouth (PS), sweat glands- increased body temp (S)
What is the mechanism and site of action of onabotulinum toxin?
inhibitor of Ach release, taken into neuron terminal via receptor mediated endocytosis, inactivates SNAP-25 required for docking of vesicle with presynaptic membrane; temporary cholinergic denervation,
What is the drug action, therapeutic use and side effects of onabotulinum toxinA?
flaccid paralysis of skeletal muscle, softens facial wrinkles, relaxes spasms, inactivates sweat glands; muscle spasms/dystonia (strabismus, blepharospasm, cervical dystonia), cosmetic, axillary hyperhidrosis, overactive bladder; dysphagia and difficulty breathing if spreads beyond injection site, ptosis, pain, allergic rxn rare
What type of signaling is utilized by M1 (CNS, ganglia) and M3 (smooth muscles, glands endothelium) receptors? general response?
Gq->PLC->inc IP3 + DAG-> inc Ca2+ + PKC; excitation/contraction/secretion
What type of signaling is utilized by M2 (heart) receptors? General response?
Gi-> dec cAMP; K+ efflux-> hyperpolarization; cell inhibition
What is the prototype agonist for M1-M5 receptors? What is the prototype antagonist?
muscarine; atropine
What is the prototype agonist for Nn receptors? Antagonist?
nicotine (high affinity, followed by desensitization), mecamylamine
What is the prototype agonist for Nm receptors? Antagonist?
nicotine (low affinity, stimulation phase obscured by desense and muscle paralysis), dtubocurarine (non-depolarizing competitive neuromuscular blockade)
What is the function and location of BuChE?
drug metabolizer of choline esters and AChE inhibitors, plasma, glial cells and liver; if deficient can cause succinylcholine induced apnea
Describe the progression of catecholamine synthesis including location. What is the rate-limiting step of all of these? What increases synthesis of EPI? how?
NE formed in adrenergic postganglionic neurons (Tyr->DOPA->DA-> active transport from cytosol to vesicle->NE); DA in basal ganglia of CNS (Tyr->DOPA->DA), EPI in adrenal medulla (Tyr->DOPA->DA-> act trans to vesicle-> NE-> leak to cytosol->EPI) RLS= tyrosine hydroxylase (Tyr->DOPA); glucocorticoids (inc PMNT)
Why are catecholamines stored in vesicles? How do they get there?
protect from MAO degradation, VMAT-2 (vesicular monoamine transport-2)
What is the mechanism of action of reserpine? Therapeutic use? Side effects?
irreversible inhibitor of VMAT-2, prevents uptake of DA and recycled NE, and reuptake of leaked transmitters, loss of symp transmission-> dec Cardiac output, and TPR lowering BP; antihypertensive and antipsychotic; SE- sedation, unopposed cholinergic (cramping, diarrhea), psychotic depression
What is the mechanism of action of the A2 receptor?
Gi-> inhibition of Ca2+ influx; - feedback of NE release
What does tyramine do? Mechanism? source? bioavailability?
stimulate NE release; displaces NE from vesicles, non-vesicular release from nerve terminals via reverse transport thru NET;fermentation byproduct of tyrosine, aged cheese, beer/wine, soy/fish, sauerkraut/kimchee, cured meats; low oral bioavil. due to GI/hepatic MAO (except when on MAO inhibitors); high systemic=hypertensive crisis
What is the mechanism of action of methyldopa? Therapeutic use? Side effects?
A2 receptor agonist, A2 stimulation in CNS reduces SNS outflow to periphery (dec CO and TPR); gestational hypertension; SE- sedation, dry mouth, edema, hemolytic anemia (Coomb’s test positive, rare life threatening, no explanation)
What is the mechanism of the receptor A1? A2?
Gq-> inc Ca2+ (SM contract), Gi-> dec cAMP (nerves)
What is the mechanism of the receptor B1? B2? B3?
Gs-> inc cAMP->PKA->Ca2+ channels (heart, kidney, excitation/contraction), Gs (relaxation, lung, skeletal muscle, uterus), Gs (lipolysis, relax, adipose, detrusor)
What is the mechanism of cocaine?
inhibitor of NE reuptake, CNS and periphery, excess NE in synapse following SNS activation
How are catecholamines metabolized? How are they targeted for diseases? Urine metabolite excreted?
MAO (mitochondria) deaminates catacholamines, tyramine, and histamine, clearing in nerve terminals, inhibitors for depression; COMT (cytosol, liver and kidney) o-methylates catechols, clearance of circulating, inhibitors for Parkinson’s; VMA
What is the mechanism of amphetamines?
promotes NE release/inhibits reuptake (ADHD)
What are the pharmacokinetic/dynamic properties of ACh?
poor lipid solubility, short duration of action (BuChE), non-selective cholinergic actions (M + Nn) at multiple sites
What are the cardiovascular effects of ACh, receptor, and receptor action?
vasodilation- M3 vascular endothelium, Gq-> PLC-> IP3-> Ca2+/calmodulin induced NO release, diffusing into adjacent smooth muscle->relaxation; (-) chronotrope via M2, (-) ionotrope via decrease Ca2+, decrease AV and SA node CV
What happens when ACh is given in the presence of atropine? Why?
ACh-induced stimulation of sympathetic ganglia-> vasoconstriction, inc. HR; Atropine is M antagonist so counteracts all M receptor effects leaving only Nn effects of ACh
What is the ophthalmic use for ACh? Adverse effects?
inject into anterior chamber, rapid and complete miosis (drops not lipid soluble enough); cataract surgery, keratoplasty, iridectomy; ciliary muscle contraction opens trabecular meshwork increasing outflow of aqueous humor (reduce intraocular pressure); rarely systemic (bradycardia, hypotension)
What are the general properties of Choline esters? Alkaloids?
more selective and prolonged action; esters don’t penetrate BBB but alkaloids do; used: bladder disorders, xrostomia and diagnosis of bronchial hyperreactivity, miosis and glaucoma
What are the properties and uses of bethanechol? Uses?
choline ester selective for bladder (detrusor) and GI M3, resistant to ChE, postoperative and postpartum urinary retention; orally for 3-4 days can avoid catheterization
What are the uses and properties of Methacholine?
inhalation-> diagnosis of hyperreactivity (asthmatics) targets bronchial M3; also used opth. for miosis and glaucoma
What are the properties and uses of pilocarpine? Uses?
prototype alkaloid; partial agonist of all M receptors; oral- for xerostomia induced by radiation or sjorgens syndrome (receptor reserve), salivary parenchyma must have residual capacity; topically- 2nd line for wide angle glaucoma, associated with ocular hypertension
What are the properties and uses of Cevimeline? Uses?
selective agonist for M1/M3 in lacrimal and salivary glands; sjogrens and xerostomia induced by radiation, longer duration and fewer side effects than pilocarpine