Compare the action potentials of a sino-atrial node cell and a myocardial cell.
A good answer included a well labelled sketch with a description of ion channels and relative
directional flow. When using sketches in an answer they should be correctly labelled, and
when used as a comparison with another sketch, the differences should be clear e.g. shape,
duration and voltage difference.
A "well labelled sketch with a description of ion channels and relative directional flow" would probably be intolerably messy because there would be a considerable amount of text present on the diagram, which in many ways defeats the objectives of having a diagram. However, to humor the examiners, such a sketch is presented below:
A more efficient use of art would be to label the phases of the cardiac action potential in a diagram and then explain their ionic correlations in a tabulated legend, as follows:
Cell | Ventricular Myocyte | Pacemaker cell |
Resting potential | -90 mV | -60 mV |
Threshold Potential | -70 mV | - 40 mV |
Phase 4 |
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Phase 0 |
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Phase 1 |
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Phase 2 |
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Phase 3 |
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Antoni, H. "Electrophysiology of the heart at the single cell level and cardiac rhythmogenesis." Comprehensive Human Physiology. Springer, Berlin, Heidelberg, 1996. 1825-1842.
Pinnell, Jeremy, Simon Turner, and Simon Howell. "Cardiac muscle physiology." Continuing Education in Anaesthesia, Critical Care and Pain 7.3 (2007): 85-88.
Bers, Donald M. "Cardiac excitation–contraction coupling." Nature 415.6868 (2002): 198-205.
Draper, Morrell Henry, and Silvio Weidmann. "Cardiac resting and action potentials recorded with an intracellular electrode." The Journal of physiology 115.1 (1951): 74-94.
Bers, Donald M. "Cardiac excitation–contraction coupling." Nature 415.6868 (2002): 198-205.
DiFrancesco, Dario. "Pacemaker mechanisms in cardiac tissue." Annual review of physiology 55.1 (1993): 455-472.
Noma, Akinori. "Ionic mechanisms of the cardiac pacemaker potential." Japanese heart journal 37.5 (1996): 673-682.
Grunnet, Morten. "Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti‐arrhythmic principle?." Acta physiologica 198 (2010): 1-48.