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Neuro II Exam 2 > Intro To Cholinergic Agonists And Antagonists > Flashcards

Intro To Cholinergic Agonists And Antagonists Flashcards

1
Q

Parasympathetics:

  • Neurotransmitters
  • Receptors
  • Locations
A
  • NT: ACh
  • Rec: nAChR, mAChR
  • Loc: cardiac and smooth muscle, gland cells, nerve terminals
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2
Q

Sympathetic:

  • NT
  • Receptors
  • Locations
A
  • NT: NE>Epi (DA); ACh
  • Rec: alpha, beta, (D), nAChR, mAChR
  • Loc: sweat glands (ACh, M); cardiac and smooth muscle, gland cells, nerve terminals (NE, alpha/beta); renal vascular smooth muscle (D, D1)
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3
Q

Cholinergic nerve terminal:

  1. ACh synthesis
  2. ACh storage
  3. ACh release
  4. ACh destruction
A
  1. Synthesized in cytoplasm: AcCoA + Choline
  2. Stored in vesicle
  3. Released into synaptic terminal to bind to mAChR and nAChR in other cell
  4. Destroyed into choline and acetate
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4
Q

Adrenergic nerve terminal:

  1. Synthesis
  2. Storage
  3. Release
  4. Reuptake
A
  1. Synthesized in cytoplasm from tyrosine to dopa to dopamine
  2. Stored in vesicle as DA and converted in vesicle to NE
  3. Released as NE into synaptic cleft to bind to alpha/beta receptors
  4. Reuptake as NE
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5
Q

Sympathetic effects and receptors on heart

A

beta1>beta2

Increase in heart rate, contractility, conduction velocity, automaticity, rate of idioventricular pacemakers

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6
Q

Parasympathetic effects and receptors of heart

A

M2>M3
Decrease in heart rate, contractility, conduction velocity
shortened AP duration
AV block

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7
Q

Sympathetic effects and receptors on blood vessels

A

Coronary: constriction, dilation. alpha1/2, beta2
Skin and mucosa: constriction. Alpha1/2
skeletal muscle: constriction, dilation. Alpha1, beta2
Cerebral: constriction (slight). Alpha1
Pulmonary: constriction, dilation. Alpha1, beta2
Abdominal viscera: constriction, dilation. Alpha1, beta2
Salivary glands: constriction: alpha1, beta2
Renal: constriction, dilation. Alpha1/2, beta1/2
Veins: constriction, dilation. Alpha1/2, beta2

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8
Q

Parasympathetic effects and receptors on blood vessels

A

Salivary glands: dilation, M3

Rest: no innervation

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9
Q

Sympathetic effects and receptors on lung

A

Tracheal/bronchial smooth muscle: relaxation, beta2

Bronchial glands: decreased/increased secretion, alpha1, beta2

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10
Q

Parasympathetic effects and receptors on lung

A

Tracheal/bronchial smooth muscle: contraction, M2=M3

Bronchial glands: stimulation, M3, M2

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11
Q

Sympathetic effects and receptors on stomach/intestine

A

Motility and tone: decrease, alpha1/2, beta1/2
Sphincters: contraction, alpha1
Secretion: Inhibition, alpha2

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12
Q

Parasympathetic effects and receptors on stomach/intestine

A

Motility and tone: increase, M2=M3
Sphincters: Relaxation, M3, M2
Secretion: Stimulation, M3, M2

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13
Q

Sympathetic effects and receptors on gallbladder

A

Relaxation, beta2

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14
Q

Parasympathetic effects and receptors on gallbladder

A

Contraction, M

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15
Q

Sympathetic effects and receptors on renin secretion

Parasympathetic?

A

Symp: decrease, increase, alpha1, beta1
Para: no innervation

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16
Q

Sympathetic effects and receptors on urinary bladder

A

Detrusor: relaxation, beta2

Trigone and sphincter: contraction, alpha1

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17
Q

Parasympathetic effects and receptors of urinary bladder

A

Detrusor: contraction, M3>M2

Trigone and sphincter: relaxation, M3>M2

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18
Q

Sympathetic effect and receptors on uterus

A

Pregnant contraction: alpha1
Pregnant relaxation: beta2
Nonpregnant relaxation: beta2

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19
Q

Sympathetic and parasympathetic effects and receptors of male sex organs

A

Sympathetic: ejaculation, alpha1
Para: erection, M3

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20
Q

Sympathetic effects and receptors of skin

A

Pilomotor muscles: contraction, alpha1

Sweat glands: localized/generalized secretion: alpha1

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21
Q

Location, structural features, mech of M1

A

Nerves
GPCR, Gq/11
IP3, DAG

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22
Q

Location, structural features, mech of M2

A

Heart, nerves, smooth muscle
GPCR, Gi
Inhibition of cAMP production, activation of K+ channels

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23
Q

Location, structural features, mech of M3

A

Glands, smooth muscle, endothelium
GPCR, Gq
IP3, DAG

24
Q

Location, structural features, mech of M4

A

CNS
GPCR, Gi
Inhibition of cAMP production

25
Q

Location, structural features, mech of M5

A

CNS
GPCR, Gq
IP3, DAG

26
Q

Describe direct-acting cholinergic agonists: choline esters

A 
MOA: agonists at cholinergic receptors
Choline esters permanently charged
Poor absorption and distribution to CNS
Metabolized by acetylcholinesterase
ACh>methacholine>carbachol=bethanecol
27
Q

Describe direct-acting cholinergic agonists: alkaloids

A

MOA: agonists at cholinergic receptors
Uncharged tertiary amines -> well absorbed (nicotine patch)
Muscarine is charged but can cross BBB and is highly toxic when ingested (mushrooms)
MAChR: muscarine and pilocarpine
nAChR: nicotine, lobeline

28
Q

What are the 3 groups of AChE inhibitors?

A
  1. Alcohols: reversible
  2. Carbamic acid esters: reversible but longer lasting than alcohols
  3. Organophosphates: irreversible (covalent)
29
Q

Describe PK and PD of AChE inhibitors

A

Chemistry dictates PK

Charged AChE inhibitors are insoluble in lipids

  • Do not cross BBB, poor PO absorption
  • Quaternary agents (edrophonium, pyridostigmine, neostigmine, echothiophate, ambenoium)

Neutral AChE inhibitors are lipid-soluble

  • Can cross BBB and readily absorbed
  • Most organophosphates, tertiary agents (physostigmine, donepezil, galantamine, rivastigmine, tacrine)

MOA: inhibition of AChE (also BuChE)

30
Q

Acetylcholine clinical use

A

Intraocular use during surgery and causes miosis (reduction in pupil size)

31
Q

Bethanechol clinical use

A

Selective mAChr agonist that primarily affects urinary and GU tracts
Used to treat pts with urinary retention and heartburn
Little cardiovascular stimulation
May produce urinary tract infection if sphincter fails to relax

32
Q

Carbachol clincal use

A

Nonspecific cholinergic agonist that is used for treatment of glaucoma or to produce miosis during surgery or ophthalmic examination

33
Q

Cevimeline clinical use

A

Oral tablet used to treat dry mouth (xerostomia) in patients with Sjogren syndrome

34
Q

Pilocarpine

A

Approved for xerostomia treatment in pts with Sjogren syndrome or head and neck cancer treatment related to xerostomia
Miosis during ophthalmic procedures (topical) and for glaucoma (topical)
Pure mAChR agonist

35
Q

Varenicline (Chantix) clinical use

A

FDA approved for smoking cessation
Partial agonist that binds with high affinity and selectivity to alpha4beta2 nAChRs (Nn)
MOA: stimulation and subsequent moderate, sustained release of mesolimbic dopamine are thought to reduce craving and withdrawal symptoms associated with smoking cessation
Nausea most common adverse side effect
Serious adverse side effects: neuropsychiatric symptoms including changes in behavior, agitation, depressed mood, suicidal ideation, and attempted and completed suicide

36
Q

Describe major uses of direct-acting cholinergic agonists

A

Diseases of eye:
Glaucoma
Accommodative esotropia: misalignment of eyes caused by hypermetropic accomodative error

GI/GU disorders:
Postoperative ileus
Congenital megacolon
Urinary retention
Esophageal reflux
Xerostomia, Sjogren syndrome
37
Q

Describe toxicity of direct-acting cholinergc agonists: muscarinic stimulus

A

Predictable: nausea, vomiting, diarrhea, urinary urgency, salivation, sweating, cutaneous vasodilation, bronchial constriction, increase in glandular secretion (SLUDGE)

Contracindicated: asthma, hyperthyroidism, coronary insufficiency, acid-peptic disease

38
Q

Describe toxicity of direct-acting cholinergic agonists: nicotinic stimulants

A

Nicotine poisoning from cigarettes and insecticides
Acute toxicity includes CNS stimulation, skeletal muscle end plate depolarization, respiratory paralysis, hypertension, cardiac arrhythmias

Treat with atropine and parenteral anticonvulsants (diazepam)

39
Q

Describe clinical uses of indirect-acting cholinergic agonists

A
  • Glaucoma: stimulation of mAChRs on ciliary body facilitates aqueous humor outflow and reduces intraocular pressure (replaced by beta-blockers, prostaglandins)
  • Dementia (Alzheimer and Parkinson): deficiency of intact cholinergic neurons (particularly those extending from subcortical areas such as nucleus basalis of Meynert)
  • Antidote to anticholinergic poisoning:
  • -from atropine, antihistamines, TCAs, sleep aids, cold preparations
  • -symptoms: cutaneous vasodilation, anhidrosis, anhydrotic hyperthermia, nonreactive mydriasis, delirium, hallucinations, reduction/elimination of desire to urinate
  • Reversal of neuromuscular paralysis
  • Myasthenia gravis
40
Q

Describe AChE inhibitor toxicity

A

SLUDGE symptoms, effects on NMJ

Treatment: atropine, maintenance of vital signs, decontamination, pralidoxime (cholinesterase regenerator)

41
Q

Compare/contrast cholinergic agonist vs cholinergic antagonist effects on organ systems

A 
Cholinergic agonist:
Eye: pupillary constriction, near vision
Salivary glands: salivation
Bronchi: constriciton, secretion
Heart: Slowing
GI tract: gastric secretion increased, colic, diarrhea
Bladder: voiding of urine
Cholinergic antagonists:
Eye: pupillary dilation, far vision
Salivary glands: dry mouth
Bronchi: relaxation, sticky dry
Heart: acceleration
GI tract: gastric secretion reduced, constipation
Bladder: retention of urine
42
Q

Describe antinicotinic and antimuscarinic agents

A

Antinicotinic agents:
Neuromuscular junction: skeletal muscle relaxants
Ganglia: rarely used

Antimuscarinic agents:
CNS, nerves, heart, smooth muscle, glands, endothelium
Block effects of parasympathetic autonomic discharge
Most clinically useful cholinergic antagonists
Protype: atropine

43
Q

Drugs used for motion sickness

A

Scopolamine

44
Q

Drugs for GI disorders

A

Atropine
Dicyclomine
Glycopyrrolate
Hyoscyamine

45
Q

Drugs used in ophthalmology

A 
Atropine
Cyclopentolate
Homotropine
Scopolamine
Tropicamide
46
Q

Drugs used for respiratory disorders

A

Ipratropium

Tiotropium

47
Q

Drugs used for urinary disorders

A 
Darifenacin
Oxybutynin
Solifenacin
Tolterodine
Trospium
48
Q

Drugs used for cholinergic poisoning

A

Atropine (+pralidoxime)

49
Q

Drugs used for movement disorders

A 
Benztropine
Biperiden
Orphenadrine
Procyclidine
Trihexyphenidyl
50
Q

Describe organ system effects of anticholinergics

A

(General increase in sympathetic tone)

CNS: sedation, drowsiness, amnesia, hallucinations, tremor reduction. Effects vary with class (atropine vs scopolamine)

Eye: Pupil dilation, cycloplegia (ciliary muscle paralysis), loss of accommodation, secreation reduction

CV system: tachycardia may occur. Little effect on blood pressure

Respiratory system: Bronchodilation and secretion reduction

GI tract: reduction in salivation, gastric secretion, prolonged gastric emptying time

GU tract: urinary retention

Sweat glands: suppression of thermoregulatory sweating by inhibiting sympathetic cholinergic nerve fibers (no parasympathetic innervation of sweat glands)

51
Q

Describe anticholinergics for CNS disorders

A

Parkinson:
MAChR antagonists can reduce tremors
Not as effective as standard dopaminergic therapy (often used in combination)
Tertiary amines benztropine, trihexyphenidyl, and procyclidine

Motion sickness:
Scopolamine: PO, injection, transdermal

Anesthesia:
Atropine given to block responses to vagal reflexes induced by surgical manipulation of visceral organs
Atropine or glycopyrrolate is paired with cholinesterase inhibitor neostigmine to block parasympathetic effects

52
Q

Describe anticholinergics for ophtalmologic disorders

A

MAChR antagonists only used when cyclopegia or prolonged mydriasis is required

  • refractive eye surgery (LASIK)
  • alpha-adrenergic receptor agonists are shorter-acting and produce less adverse effects

Homatropine and atropine are used to prevent synechia formation in uveitis and iritis (where iris adheres to either lens or cornea)

  • long-acting agents
  • mydriasis may last 6 hours to 12 days , and cycloplegia persists about 10 hours to 14 days
53
Q

Anticholinergics for respiratory disorders

A

Asthma and chronic obstructive pulmonary disease (COPD)

Ipratropium and tiotropium

  • inhalation mAChR antagonists
  • tiotropium has a longer bronchodilator action than ipratropium and can be dosed once daily

MACH antagonists such as atropine and scopolamine were used in preoperative settings to limit airway secretions that were increased by irritant anestehtics (ether)
-Now replaced by inhalational anesthetics

54
Q

Describe anticholinergics for GI disorders

A

MAChR antagonists used in treatment of common traveler’s diarrhea and other mild and self-limited conditions of hypermotility

Side effects and alternative therapies limit use

Often combined with opioid antidiarrheal drug to discourage abuse of opioid agent
Ex: lomotil: combination of atropine and diphenoxylate

55
Q

Describe anticholinergics for GU disorders

A

MAChR antagonists can provide symptomatic relief in treatment of urinary urgency caused by minor inflammatory bladder disorders

Agents with selectivity to M3 subtype of mAChR are beneficial due to presence in bladder wall and sphincter smooth muscle

Oxybutynin: prototype selective M3 antagonist but has side effects (dry mouth/eyes, dizziness, constipation, blurred vision)

Darifenacin, solifenacin, and tolterodine are selective for M3 subtype and are advantageous because of longer half-lives and reduced incidence of xerostomia and constipation

56
Q

Describe anticholinergics for cholinergic poisoning

A

Medical emergency that can be caused by cholinesterase inhibitor insecticides, wild mushrooms, chemical warfare nerve gases

Antimuscarinic agents (atropine) given to reduce mAChR stimulation

No effective treatment at nAChR (pralidoxime)

Atropine is useless in delayed-onset mushroom poisoning
-characterized by vomiting and nausea 6-12 hrs after ingestion and causes hepatic/renal cellular injury by amatoxins that inhibit RNA polymerase

57
Q

Describe adverse effects and contraindications of anticholinergics

A

Good for one organ, bad for another
-mydriasis and cycloplegia may be adverse effects if muscarinic agents used to reduce GI secretion

High systemic concentrations lead to block of parasympathetic function

  • dry as a bone, blind as a bat, red as a beet, mad as a hatter, hot as a hare
  • treat with AChE inhibitors or symptomatically

Contraindications/caution:
Glaucoma
Prostatic hyperplasia
Acid-peptic disease

Neuro II Exam 2 (6 decks)

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