Which of the following statements about the action potential in contractile card

ID: 3481015 • Letter: W

Question

Which of the following statements about the action potential in contractile cardiomyocytes is NOT true?

a) The initial rapid depolarization of the cell membrane in an AP is due to opening of voltage-gated Na+ channels.

b) Voltage-gated Ca2+ channels are responsible for the prolonged depolarization (the plateau phase) of the action potential.

c) Because cardiac muscle cells do not have voltage-gated K+ channels, the AP has a prolonged depolarization (the plateau phase)

d) During the effective refractory period, a muscle cell cannot be stimulated to contract again by normal physiological mechanisms

e) The effective refractory period lasts until the cell membrane has almost completely repolarized.

The cardiac action potential cosists of rapid depolarisation, plateau phase, rapid repolarisation and refractory phase

during the plateau phase of cardiac muscle repolarisation occur very slowly and the membrane poential remains almost the same.

THE plateau phase occurs due to movement of the charges in and out of cell. the potassium ions move out of cell and calcium ions move into the cell.

cardiomyocytes contain K+ channel which are characterised by low conduction for potassium which increases slowly.

cardiomyocytes also contain calcium channel - Lcalcium channel which opens very slowly but remains open for longer period.

This balance between the influx of calcium and efflux of sodium cause long plateau phase

from the above explaination it is clear that cardiomyocytes contain potassium channel

so the answer is C .

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