How does increasing the extracellular calcium concentration lead to a decrease in excitability? A) Ca²⁺ can block Na⁺ channels, so the extra concentration means fewer channels are available for Na⁺ to move through. B) Ca²⁺ increases the voltage threshold required to open the Na⁺ channels, so the extra concentration means channels require more stimulus. C) Ca²⁺ decreases the voltage threshold required to open the K⁺ channels, so the extra concentration means K⁺ channels will open sooner, hyperpolarizing the cell. D) It makes the outside of the cell more positive, so by comparison the inside is more negative and therefore less likely to depolarize.

Question

Quizplus · Accepted Answer

Increasing the extracellular calcium concentration increases the voltage threshold required to open the Na+ channels. This means that more stimulus is required to open the channels and depolarize the cell, ultimately leading to a decrease in excitability.

How Does Increasing the Extracellular Calcium Concentration Lead to a Decrease