The extraglomerular mesangial cells help with the signalling between macula densa cells and juxtaglomerular cells.

球外系膜细胞辅助致密斑和球旁细胞的信息传递过程。

The juxtaglomerular cells then receive the signal and also independently sense the low pressure in the blood vessels and secrete an enzyme called renin which increases sodium reabsorption which helps raise the blood volume.

球旁细胞接收信号，同时也可感受血管低血压，并分泌一种叫肾素的酶，而肾素能增加钠的重吸收，从而能增加血容量。

Each nephron also has a really unique region called the juxtaglomerular complex which is involved in the regulation of blood pressure and the glomerular filtration rate —or the amount of blood that passes through the glomeruli each minute.

每个肾单位有一个独特的区域，称为球旁复合体；球旁复合体与血压的调控和肾小球滤过率（每分钟流经肾小球的血量）有关。

So, in the case of hypovolemia and hypotension, the macula densa cells sense the low sodium and chloride levels and send a signal over to the juxtaglomerular cells which are located in the wall of the afferent arteriole.

因此，当血容量减少、低血压时，致密斑感受到钠、氯含量降低，传递信号给位于入球小动脉血管壁上的球旁细胞。