Week 17: (B) The effect of beta-adrenoreceptor Ligand Upon the Heart Flashcards
What are the catecholamines agonists?
Dobutamine, adrenaline & noradrenaline
What do the agonist increase agonist?
increase force, rate and cardiac output & O2 consumption
What do the agonists decrease?
-Cardiac efficiency (O2 consumption increase more than cardiac work)
• can cause disturbances in cardiac rhythm (arrhythmias)
What are the clinical uses of adrenaline?
- Cardiac arrest (sudden loss of pumping function)
- Emergency treatment of asthma
- Anaphylactic shock
What are the clinical uses of Dobutamine?
(selective for Beta1-adrenoreceptors).
acute, but potentially reversible, heart failure e.g. following cardiac surgery, or cariogenic shock
What is a non selective Beta-blocker?
propranolol, antagonist of beta1 and beta 2
What are the pharmacodynamic effects of antagonists?
- At rest; little effect on rate, force, CO or MABP.
- During exercise; decrease rate, force and CO.
What is effect of antagonists on mammal exercise tolerance?
reduced
What effect does antagonist have on coronary vessel diameter?
slightly reduced (beta2-adrenoreceptor controls vasodilation)
What are the selective blockers of the beta 2 receptor?
metoprolol and atenolol
What are clinical uses of the beta-Andrenoreceptor antagonist?
1) Treatment of disturbances of cardiac rhythm (dysrhythmias)
2) treatment of hypertension
3) treatment angina
4) treatment heart failure
What can sessile sympathetic activity lead to?
tachycardia
or spontaneous activation of ‘latent cardiac pacemakers’ outside nodal tissue.
What to beta blockers do?
decrease excessive sympathetic drive and help
restore normal sinus rhythm (i.e. rhythm driven by the SA node)
How does the non-selective muscarinic antagonist Atropine effect pharmacodynamics?
-Modest increase in heart rate (tachycardia)
in normal subjects
-More pronounced
effect in highly trained athletes (who have
increased vagal tone)
-No effect upon arterial BP (resistance
vessels lack a parasympathetic innervation)
• No effect upon the response to exercis
What are the clinical uses of Atropine?
-Reverse bradycardia following myocardial infarction (in which
vagal tone is elevated).
-anticholinesterase poisoning (to reduce excessive
parasympathetic activity)
