Students lose balance over the yin-yang of sodium physiology

Abstract

One of the major areas that students studying physiology stumble over is sodium homeostasis. In particular, there is often an unclear separation in their understanding to differentiate between sodium balance and sodium concentration (NaC) control. Functionally, students need to understand that NaC control involves the osmoreceptors that monitor changes in NaC in the extracellular fluid (ECF) since NaC is the dominant determinant of ECF osmolarity. This teaching note aims to address the common misconception regarding sodium physiology, specifically that ECF NaC is not regulated by the renin-angiotensin-aldosterone (RAAS) family of hormones. The RAAS is instead directed toward total body sodium or sodium balance. Different scenarios of ECF changes that alter sodium balance and/or NaC will be illustrated with a summary of “Tables of Salt.” Hopefully, both students and teachers will find this teaching note useful in their appreciation of the wonderful Yin Yang of sodium physiology.

Keywords

• Homeostasis
• physiology
• sodium