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Physiology

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Cardiovascular System

Question
7 out of 13
 

Calcium enters the cardiac cell during:



A Rapid upstroke of the action potential

B Down slope of the action potential

C Plateau phase of the action potential

D Slow diastolic depolarization (phase 4) of the action potential

Ans. A Endocardium, epicardium, upper most part of septum

1. Depolarization started from SA node spreads radially all over the atria and converges on AV node arid this process takes 0.1 seconds.

2. As the conduction in AV node is slow, wave of excitation spreads to ventricles after another 0.1 second.

3. From top of septum the wave spreads rapidly in Purkinje fibers and ventricles in 0.08 to 0.1 seconds.

4. Ventricular depolarization starts at the left side of interventricular septum and moves to right across the middle portion of septum.

5. From here it spreads down the septum to the apex of heart and returns along the ventricular wall to the AV junction. Endocardium is stimulated, then myocardium, and then the epicardium. Last parts of heart to be depolarized are postero-basal part of left ventricle, pulmonary conus and finally upper most portion of septum.

Cardiovascular System Flashcard List

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