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55 Cards in this Set
- Front
- Back
SNS regulates these 2 major things. Especially in response to what? What mediates the SNS stimulation?
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Heart & Peripheral Vasculature
Stress NE (& Epi from adrenal medulla) |
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Drugs that mimic the actions of Epi or NE are called what?
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Sympathomimetic drugs
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List 3 modes of action of Indirecting acting Adrenoceptor-activating agents
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1. promote release of Endogenous Catecholamines
2. displace stored catecholamines = Amphetamine & Tyramine 3. inhibit reuptake of Catecholamines (Cocaine) |
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What is the function of Alpha-1 Adrenoceptors?
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Contraction of Smooth Muscle
-Peripheral Vasculature = increase BP -GI & Bladder sphincters = urinary retention -radial muscle of iris = mydriasis -Kidney = decrease Renin release |
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What is the mechanism of action of the Alpha-1 adrenoceptors?
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Activation of Gq
1. stimulate PIP2 hydrolysis 2. formation of IP3 -> Ca++ mobilization 3. formation of DAG -> PKC activation 4. Phospholipase C activation |
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What is the function of the Alpha-2 adrenoceptors?
What is the mechanism of action? |
Presynaptic autoregulation of neurotransmitter release
1. activate Gi 2. inhibition of Adenylyl Cyclase 3. decrease in cAMP **MAD 2's |
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Define the affinity of Beta-1 adrenoceptors for Epi & NE
Define the affinity of Beta-2 adrenoceptors for Epi & NE |
Beta-1 --> Epi = NE
Beta-2 --> Epi > NE |
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Where are Beta-1 receptors located?
What is their mechanism of action? |
SA node, AV node, and Ventricular muscle of the heart
1. activate Gs 2. stimulate Adenylyl Cyclase 3. increase cAMP levels |
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Where are the Beta-2 adrenoceptors located?
What is their mechanism of action? |
VENOUS vascular smooth muscle, bronchial smooth muscle, and in walls of GI tract & bladder
1. activate Gs 2. stimulate AC = increase cAMP levels |
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Whare are Dopamine receptors located? (3)
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1. Brain
2. Splanchnic vasculature 3. Renal vasculature |
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What is the difference b/w D1 and D2 adrenoceptors?
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D1 = stimulates AC (Gs)
D2 = inhibits AC (Gi) |
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What is the parent compound of the Catecholamines? Substitutions at what positions yields different catecholamines?
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Phenyl-ethyl-amine = benzene ring with ethylamine side chain
positions 3 & 4 |
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Adrenoceptors & Blood Vessels:
1. receptors present on the ARTERIAL smooth muscle = vasoconstriction 2. receptors present on the VENOUS smooth muscle = capacitance 3. receptors on the Skeletal muscle vessels 4. receptors that stimulate Renin secretion 5. receptors that inhibit Renin secretion |
1. Alpha-1
2. Beta-2 = relax smooth muscle 3. Beta-2 = relax smooth muscle & allow blood to flow into muscles 4. Beta-1 5. Alpha-1 |
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Adrenoceptor that is dominant in the Heart
What is the function? |
Beta-1
results in increased Ca++ influx in cardiac cells = positive inotrophy (faster) & chronotrophy (harder) -AV conduction velocity increased -refractory period decreased **with normal reflexes, HR is dominated by Vagal tone (Muscarinic)!!! = trumps sympathetic |
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What effect do Alpha agonists have on the Eye?
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contract Radial Pupillary Dilator muscle = Mydriasis = excessive dilation of pupil
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What effects do Beta agonists have on the Eye?
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Increase Aqueous Humor secretion from the Ciliary Epithelium
**Beta-antagonists are important in the treatment of Glaucoma |
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Respiratory Tract
1. What are the effects of Beta-2 receptors? 2. What are the effects of Alpha-1 receptors? |
1. Bronchodilation
2. present in blood vessels of upper respiratory musoca = contraction produces DECONGESTION |
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GI tract:
1. what are the effects of Beta receptors? 2. Alpha-2 activation effect? |
1. present on smooth muscle cells = mediate relaxation
2. decreases PNS drive on enteric system ***major effect*** |
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What adrenoceptors are present in the GU tract? What are their functions?
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Alpha-1 = contract bladder base, urethral sphincter = urinary retention
Beta-2 = relax smooth muscle in the bladder wall = promotes urinary retention |
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What adrenoceptors are present on the Exocrine glands? What is the function?
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Alpha-1 on Apocrine (stress) sweat glands
Sweating on palms, brow, upper lip |
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List the effects Beta-adrenoceptor activation has on metabolism
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1. increases Lipolysis
2. enhances Glycogenolysis 3. increases Glucose release 4. increases Insulin secretion (in response to high serum glucose) |
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What adrenoceptor decreases Insulin release?
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Alpha-2
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Is Insulin increased or decreased during SNS discharge? Why?
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Increased due to high serum glucose levels
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Endogenous catecholamine that has relatively little effect on Beta-2 adrenoceptors
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Norepinephrine = does not cause Venodilation
**but has similar potency to Epi at Beta-1 |
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What are the major effects of Epi release?
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Potent vasoconstriction (alpha-1) and Cardiac stimulant (beta-1)
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Explain the differences in the effects of Epi & NE
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Epinephrine
-potent vasoconstrictor (alpha-1) & cardiac stimulant (beta-1) -Venodilation due to Beta-2 = venous capacitance Norepinephrine -little effect on Beta-2 = no venous capacitance -increases BOTH diastolic and systolic BP -peripheral vagal reflexes overcome direct positive chronotrophy |
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Positive nonselective Beta-receptor agonist (Beta-1 = Beta-2)
What are its effects? |
Iso-proter-enol
Beta-1 = increase HR, contractility Beta-2 = decrease diastolic & mean arterial pressures (venodilation) |
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What effects does Dopamine have?
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activates D1 receptors in Renal Vasculature ➡ increases renal blood flow
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Relatively Beta-1 selective synthetic catecholamine that also activates Alpha-1 receptors (Beta-1 > Beta-2)
What is it useful for? |
Dobutamine
Cardiovascular insufficiency |
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Norepinephrine:
-big increase in resistance = due to Alpha-1 that is unopposed by Beta-2 -Unopposed resistance causes increased Blood Pressure = increased in both Diastolic and Systolic pressures; MAP also increases -Increased MAP ➡ Vagal response ➡ decreased HR due to PSNS activation of muscarinic receptors |
What catecholamine would cause this? Explain
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Epinephrine
-Alpha-1 = Arterial constriction -Beta-2 = venous dilation -MAP doesn’t change -Widening of Pulse pressure due to Arterial constriction & venodilation -Beta-1 causes increased HR **Epi stimulates all Alpha's & Beta's |
What would produce this response?
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Isoproterenol = selective Beta-agonist (Beta-1 = Beta-2)
-Beta-1 = increased HR -Beta-2 = venodilation = decreased peripheral resistance -Systolic goes slightly up due to increased HR & CO from Beta-1 -since MAP is not changed much ➡ no reflex |
What would cause this effect? Explain
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Prototypic Alpha-1 agonist
What is another alpha-1 agonist? |
Phenyl-ephrine
Methox-amine |
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Why does Phenylephrine have a longer duration of action than the Catecholamines?
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It is not a catechol derivative = not inactivated by MAO or COMT
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What is Phenylephrine used clinically for?
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Alpha-1 agonist
1. Mydriatic = pupil dilator 2. Decongestant **can also raise blood pressure if used at high levels |
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Fisrt orally active Sympathomimetic drug
What activity does it have? |
Ephedrine
Alpha agonist, displaces NE from vesicles (major effect) |
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Widely available OTC decongestant
What is it's MOA? |
Pseudoephedrine
Direct alpha adrenoceptor activation & indirect effects causing release of endogenous NE |
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2 direct Alpha-1 agonists that are used as topical decongestants (nasal spray)
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Oxy-metaz-oline
Xylo-metaz-oline |
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List 4 Alpha-2 selective agonists
What are they used as? |
Clonidine
Methyldopa Guanfacine Guanabenz Anti-hypertensives b/c inhibit release of endogenous NE |
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List 2 Beta-1 selective agonists
What do they do? |
Dobut-amine
Pre-nalt-erol (partial agonist) Increase Cardiac Output with less reflex tachycardia -don't cause the Beta-2 stimulated venodilation |
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List 4 Beta-2 selective Agonists
What are they used to treat? |
Albuterol
Salmeterol Terbutaline Rito-drine Asthma Uterine relaxation in premature labor (Ritodrine) |
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Beta-2 selective agonist used for uterine relaxation in premature labor (prevent premature labor)
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Rito-drine
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Indirect sympathomimetic that enters presynaptic neuron via Uptake 1 and releases stores of catecholamines
-marked stimulant effects on mood and alertness -depressant effect on appetite -commonly abused drug |
Amphetamine
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What is the difference between Amphetamine and Methamphetamine
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Methamphetamine has a higher ratio of central to peripheral actions
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Amphetamine variant used in ADHD due to less stimulant effects
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Methylphenidate
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What is the mechanism of action of Cocaine?
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Sympathomimetic that blocks Uptake 1
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Tyramine
1. mechanism of action 2. where is it found? 3. what potentiates its effects? 4. what can it produce? |
1. gets in via uptake 1 ➡ has high affinity for VMAT ➡ shoved into vesicles ➡ pushes NE out
2. Fermented foods (cheese) and aged foods 3. MAO inhibitors 4. Hypertensive crisis |
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In what conditions would Sympathomimetics be used to increased blood flow or pressure?
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1. Hypotension (secondary to Cardiac Arrhythmias, neurologic disease)
2. Hypovolemic or Cardiogenic shock 3. Cardiac insufficiency |
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What would be used to cause Hemostasis for Surgery?
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Cocaine = causes vasoconstriction
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What would be used to reduce diffusion of Local Anesthetics?
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Epi
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What sympathomimetics would be used to reduce mucous membrane congestion?
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Alpha-1 agonists
-Phenylephrine -Methoxamine -Oxymetazoline |
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What might be used to treat Heart Failure?
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Dobutamine (Beta-1 agonist)
**but tolerance/desensitization limits used |
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What sympathomimetic would be used for Fundoscopic examination of the retina?
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Alpha-1
-Phenylephrine -Methoxamine -Oxymetazoline |
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What sympathomimetic would be used to treat Narcolepsy (daytime sleepiness)?
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Amphetamines produce alertness and defer sleep
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What would be the symptoms of toxicity of Sympathomimetic drugs?
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1. Hypertension
2. Tachycardia 3. CNS -restlessness -tremor -insomnia -anxiety -paranoia |