Therefore, to raise blood pressure, the body will first cause an increase in sympathetic nerve activity to the SA node, causing it to fire more frequently, which increases the heart rate.

因此，要升高血压，身体首先会引起SA结交感神经活动增加，使其更频繁地放电，从而增加心率。

This typically happens when atrial cells get irritated and stressed - the causes of that might include electrolyte imbalances, drugs like cocaine or methamphetamines, ischemic damage like a heart attack, or anything that increases sympathetic activity, like anxiety.

这通常发生于心房细胞受到激惹和应激时，原因可能包括电解质紊乱、使用可卡因或麻黄碱类药物、心肌梗死等缺血性损伤，或焦虑等增高交感神经活性的因素。