Final answer:
Aldosterone is responsible for regulating Na+ and K+ levels and is stimulated by changes in blood volume, blood pressure, Na+, or K+ levels. It plays a critical role in the RAAS to control blood pressure and electrolyte balance.
Step-by-step explanation:
The correct description that explains what aldosterone regulates, and how it is stimulated, is option b) Aldosterone regulates sodium and potassium levels and is stimulated by low blood volume and pressure. Aldosterone, being the main mineralocorticoid, is essential in the regulation of sodium (Na+) and potassium (K+) ion concentrations in urine, sweat, and saliva.
It is released in response to low blood pressure or low blood volume as part of the renin-angiotensin-aldosterone system (RAAS). When blood pressure drops, cells in the juxtaglomerular apparatus release renin, initiating a cascade that ultimately increases Na+ reabsorption, leading to water retention and an elevation in blood pressure. Additionally, aldosterone release is triggered by either a decrease in blood Na+ levels or an increase in blood K+ levels.