Week 17: (B) The effect of beta-adrenoreceptor Ligand Upon the Heart

Question 1

What are the catecholamines agonists?

Answer 1

Dobutamine, adrenaline & noradrenaline

Question 2

What do the agonist increase agonist?

Answer 2

increase force, rate and cardiac output & O2 consumption

Question 3

What do the agonists decrease?

Answer 3

-Cardiac efficiency (O2 consumption increase more than cardiac work)
• can cause disturbances in cardiac rhythm (arrhythmias)

Question 4

What are the clinical uses of adrenaline?

Answer 4

• Cardiac arrest (sudden loss of pumping function)
• Emergency treatment of asthma
• Anaphylactic shock

Question 5

What are the clinical uses of Dobutamine?

Answer 5

(selective for Beta1-adrenoreceptors).

acute, but potentially reversible, heart failure e.g. following cardiac surgery, or cariogenic shock

Question 6

What is a non selective Beta-blocker?

Answer 6

propranolol, antagonist of beta1 and beta 2

Question 7

What are the pharmacodynamic effects of antagonists?

Answer 7

• At rest; little effect on rate, force, CO or MABP.

- During exercise; decrease rate, force and CO.

Question 8

What is effect of antagonists on mammal exercise tolerance?

Answer 8

reduced

Question 9

What effect does antagonist have on coronary vessel diameter?

Answer 9

slightly reduced (beta2-adrenoreceptor controls vasodilation)

Question 10

What are the selective blockers of the beta 2 receptor?

Answer 10

metoprolol and atenolol

Question 11

What are clinical uses of the beta-Andrenoreceptor antagonist?

Answer 11

1) Treatment of disturbances of cardiac rhythm (dysrhythmias)
2) treatment of hypertension
3) treatment angina
4) treatment heart failure

Question 12

What can sessile sympathetic activity lead to?

Answer 12

tachycardia

or spontaneous activation of ‘latent cardiac pacemakers’ outside nodal tissue.

Question 13

What to beta blockers do?

Answer 13

decrease excessive sympathetic drive and help

restore normal sinus rhythm (i.e. rhythm driven by the SA node)

Question 14

How does the non-selective muscarinic antagonist Atropine effect pharmacodynamics?

Answer 14

-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

Question 15

What are the clinical uses of Atropine?

Answer 15

-Reverse bradycardia following myocardial infarction (in which
vagal tone is elevated).
-anticholinesterase poisoning (to reduce excessive
parasympathetic activity)

Question 16

What’s Digoxin?

Answer 16

A Cardiac Glycoside That Increases

Contractility of the Heart

Question 17

Effects of Digoxin?

Answer 17

-Heart failure – a CO insufficient to provide adequate tissue
perfusion
-Many causes – but ultimately the ventricular function curve is
depressed
-Inotropic drugs (e.g. digoxin, dobutamine) enhance contractility