Cardiac Muscle Contraction Quiz

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Excitation contraction coupling in the myocardial cells is the process where the depolarization wave is propagated over the cardiac muscle fibers then spreads through T-tubules → release of ______ from the terminal cisternae of sarcoplasmic reticulum.

Ca++

The released ______ binds to troponin C.

Ca++

The strength of cardiac muscle contraction is directly proportional to the concentration of ______ in the extracellular fluid.

calcium

Extracellular calcium enters via L-type Ca++ channels during action potential along ______.

T tubules

At the end of plateau of cardiac muscle, Ca++ influx is suddenly stopped and active pumping (reuptake) of Ca++ occurs into SR by Ca++ ATP ase, and outside the cell through T tubules by ______-Ca++ exchanger.

Na+

According to Starling's law, an increase in venous return leads to an increase in initial length (EDV) which results in an increase in ______.

force of contraction

Within certain limits, the greater the initial length of the cardiac muscle fibers, the greater the ______.

force of contraction

Positive inotropic agents lead to an increase in ______.

contractility

Vagal tone reduces SAN rhythm from 120 beat/min to 70 beat/min, blocking vagus with atropine results in an increase in ______.

HR (heart rate)

Marked increase in extracellular K+ may stop the heart in ______.

diastole

Test your knowledge on the ability of the cardiac muscle to convert chemical energy into mechanical energy for pumping blood. Explore topics like excitation-contraction coupling in myocardial cells and the process of cross bridge cycling for contraction.

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