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In certain cardiac muscle cells, the
membrane potential gradually becomes less negative, until it
reaches a threshold. At this
point,voltage-gatedCa++
channels open.
Q.
Is this positive or negative feedback?
-Positive
The
influx of Ca++ ions causes membrane
depolarizationandtriggers
the cell to
contract.
Afterwards,
K+ channels open. K+ flows into the cell, down its
concentration gradient, repolarizing the cell.
Then,
the Na+/K+ pump goes back to work to return the cell to its
initial state.
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