This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Body Fluids, Subject name: Physiology
Potassium in which compartment is responsible for cardiac and neural function? 
Select and explain. 
A. Intracellular, B. Extracellular, C. Intravascular, D. Extravascular
A: Intracellular
Answer: A: Intracellular 
Explanation: ANSWER: (A) IntracellularREF: Guyton's physiology 11th edition page 46 & 358, Ganongs 22nd edition chapter 1''Potassium cations are important in neuron (brain and nerve) function, and in influencing osmotic balance between cells and the interstitial fluid"* Potassium is the most abundant cation in intracellular fluid.* Phosphate is the most abundant intracellular anion.* Sodium is the most abundant extracellular cation.* Chloride is the most abundant extracellular anion.