What is a typical response of the body to low serum potassium levels?

The correct response to low serum potassium levels involves a complex interaction within the body to restore potassium homeostasis. When serum potassium levels drop, one of the key physiological mechanisms activated is the secretion of hormones that help regulate potassium balance.

In this context, insulin plays a significant role. Insulin prompts cells to take up potassium from the bloodstream, thereby helping to lower serum potassium levels. This occurs as insulin facilitates the movement of potassium into cells, counteracting low serum potassium concentrations. This process is particularly crucial after meals, where increased glucose and insulin levels help ensure that potassium is effectively utilized by the body's tissues, especially muscle cells.

Regarding the other choices, increased muscle excitability typically occurs with high potassium levels, as potassium is crucial for maintaining the resting potential of muscle cells. A decreased heart rate may occur with higher potassium levels due to its effects on cardiac electrical stability, but it would not be a typical response to low levels. Finally, increased renal excretion of potassium is typically a compensatory mechanism seen when serum potassium levels are high, not low. The kidneys adjust potassium levels in response to dietary intake and bodily needs, which is opposite to the situation described in the question.