Q71 - Reading Cardiac Action Potential Phases from Ion Movements
The action potential of cardiac muscle cells differs from that of other cells such as skeletal muscle cells and neurons. Figure Q.71 displays the different phases of action potential in cardiac muscle cells, with numbered points 1 through 5 marking the resting level, the rapid depolarization upstroke, the initial partial repolarization, the plateau phase, and the return to resting potential.
Figure Q.71
Figure 1.
Using the information and data, determine which of the statements are true or which are false.
A. A substance that inhibits the reuptake of Ca2+ into the sarcoplasmic reticulum increases the time interval from 3 to 4.
B. The concentration of K+ in the sarcoplasm at position 2 is higher than that at position 3.
C. Injection of adrenaline decreases the time interval from 1 to 5.
D. The height of action potential (from 1 to 2) is decreased when the sarcoplasmic level of Na+ is higher than the normal level.
Question reproduced from IBO 2016, Theoretical Paper B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)