RLD47

Oh! My med-surg book is really off then! It says "Low serum potassium levels increase the difference in the amount of potassium between the fluid inside the cells, and the fluid outside the cells. This increased difference reduces the excitability of cells. As a result, the cell membranes of all excitable tissues, such as nerve and muscle, are less responsive to normal stimuli." That's from the Ignatavicius med surg book. (See why I am so confused) I understand the effects of potassium on the heart, my question is about the changes in intestinal motility caused by hypokalemia and hypomagnesemia. But if my book is wrong, then it makes complete sense! lol

I'm having trouble understanding the relationship between potassium, and magnesium, mostly related to the bowels. I know that hypomagnesemia causes increased membrane excitability, and hypokalemia causes cells to be less responsive to normal stimuli. My confusion, is that constipation/decreased motility accompanies both imbalances. It seems to make sense in terms of hypokalemia, because of the decrease in excitability of cells. But, if magnesium normally inhibits nerve transmission, it doesn't make sense to me why having low magnesium levels wouldn't cause increased intestinal motility instead of decreased. I've tried finding the answer in every resource available to me, with no luck. Any help is appreciated!