7 Questions
During which phase of the action potential do inward positive current stops?
Phase 3
Which ion is responsible for the small outward positive current during the plateau phase?
K+
What is the role of the Na+-Ca++ exchanger during the late part of the plateau phase?
It produces inward positive current
Which ion channels are responsible for maintaining the membrane potential nearly constant during the plateau phase?
K+ channels
What causes the repolarization in phase 3 of the action potential?
Activity of inwardly rectifying K+ channels
What is the duration of the plateau phase in ventricular myocytes?
200 msec
Which ion is carried out by the Na+-Ca++ exchanger during the late part of the plateau phase?
Ca++
Test your knowledge on the maintenance of ionic concentrations in cardiac myocytes, including the role of inwardly rectifying potassium channels, influx of Na+ and Ca++ ions, and Na+-K+ ATPase activity. Understand how these mechanisms contribute to the resting membrane potential.
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