Cardiac Muscle, Dr. D. Penney

Self Assessment:

1) Cardiac muscle cells continue to divide and synthesize myosin and actin until shortly after the time of birth (T / F).

2) Phase zero of the action potential is almost finished before peak twitch tension occurs (T / F).

3) In pacemaker cells, the rate of rise of the pre-potential may be (increased / decreased) by the presence of acetylcholine, (increasing / decreasing) the firing rate.

4) Calcium for muscle activation comes from the sarcoplasmic reticulum and from (.......................................).

5) Increasing the preload, increases the strength of contraction and (increases / doesn't change / decreases) the maximal velocity of shortening?

6) Increasing the inotropic state, increases the maximal velocity of shortening and (increases / doesn't change / decreases) the strength of contraction.

7) The slow inward flow of Ca++ ions through slow channels is responsible for phase (0 / 1 / 2 / 3 / 4).

8) Maximal efficiency of work occurs at intermediate load and velocity of shortening (T / F).

9) The absolute refractory period in cardiac muscle prevents tetanus, circus movements and ineffective tachycardias (T / F).

10) Norepinephrine has a direct action on the heart of (increasing / decreasing) the diastolic potential.

11) The effect of increasing cycle length on the cardiac action potential of a follower cell is to (increase / decrease) intracellular Ca++ concentration.

12) Treppe in heart muscle involves tetany. (T / F)

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