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Pharmacology

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Autonomic Nervous Systems

Question
41 out of 75
 

All of the following are actions of epinephrine on beta-receptors except



A Tachycardia

B Ventricular arrhythmias

C A-V block

D Increased cardiac output

Ans. C A-V block
  1. Epinephrine is a powerful cardiac stimulant and it acts directly on the predominant beta-2 receptors of the myocardium and of the cells of the pace maker and conducting tissues.
  2. The heart rate increases, and the rhythm is often altered. Cardiac systole is shorter and more powerful, cardiac output is enhanced and the work of the heart and its oxygen consumption are markedly increased. However, cardiac efficiency (work done relative to oxygen consumption) is lessened.
  3. Direct responses to epinephrine include increase in contractile force, accelerated rate of rise of isometric tension, enhanced rate of relaxation, decreased time to peak tension, increased excitability, acceleration in the rate of spontaneous beating, induction of automaticity in specialized regions of the heart.

Autonomic Nervous Systems Flashcard List

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