每日一题_2022.12.13

A 55-year-old man with hypertension is pre- scribed an antiarrhythmic agent that alters the flow of cations in myocardial tissue. The image is a trace of a myocardial action potential. Each phase is associated with the opening and/ or closing of various ion channels. Which of the following would be affected by an agent that affects phase 0 of the myocardial action potential?

1例55岁男性高血压患者，预先接受了改变心肌组织中阳离子流动的抗心律失常药物。图像是心肌动作电位的痕迹。各相与各种离子通道的开放和（或）关闭有关。影响心肌动作电位0相的药物会影响以下哪一项？

(A) Ligand-gated calcium channels opening

(B) Ligand-gated potassium channels closing

(C) Ligand-gated sodium channels opening

(D) Voltage-gated calcium channels opening

(E) Voltage-gated potassium channels closing

(F) Voltage-gated sodium channels closing

(G) Voltage-gated sodium channels opening

答案解析：

电压门控Ca + 通道（L型）在钠上升（约-40 mV）时缓慢打开，使钙沿其浓度梯度流入细胞。同时，存在通过电压门控通道的外向钾电流，导致平台期。其结果是传导缓慢，使心房到心室的传导时间延长。

正确答案：G