When KATP channels are open, which ion movement predominates?

When KATP channels are open, which ion movement predominates?

• A. Sodium influx
• B. Potassium efflux
• C. Calcium influx
• D. Chloride influx

Answer: (B)

Opening these channels lets potassium leave the cell. They are highly selective for K+, and with intracellular K+ much higher than outside, the gradient drives K+ outward when the channel is open. The outward K+ current hyperpolarizes the membrane, reducing excitability and calcium entry. This outward movement is the dominant flux because other ions don’t pass through these channels in significant amounts.

Opening these channels lets potassium leave the cell. They are highly selective for K+, and with intracellular K+ much higher than outside, the gradient drives K+ outward when the channel is open. The outward K+ current hyperpolarizes the membrane, reducing excitability and calcium entry. This outward movement is the dominant flux because other ions don’t pass through these channels in significant amounts.