The urinary system plays a vital role in maintaining the delicate ion balance of the body.
One of the ions it helps to regulate is potassium (K+). K+ is a hugely important electrolyte within the body and plays a vital role in maintaining the resting membrane potential of cells. Even a small change in the extracellular concentration of K+ could depolarize or hyperpolarize cells quite significantly, which has big implications for cardiac function amongst other things.
The normal concentrations of K+ in each vary somewhat but are said to be between 3.5-5.0 mmol/L in the ECF and between 120-150 mmol/L in the ICF. 98% of the body’s K+ is stored intracellularly.
The concept of maintaining an internal balance of K+ refers to its movement between the extracellular fluid (ECF) and intracellular fluid (ICF).
The external balance of K+ is regulated by the kidneys and refers to its filtration and subsequent reabsorption and secretion within the nephron – this can be adjusted depending on potassium intake and use within the body.
The urinary system also plays a role in maintaining acid-base balance in the body via movement of ions and the buffering system. The acid-base balance is vital for normal bodily functions and when disrupted severe symptoms such as arrhythmias and seizures can occur.