Final answer:
Potassium toxicity or hyperkalemia occurs under conditions of excessive potassium intake, leading to serious symptoms like cardiac arrhythmias and muscle paralysis, which can be fatal.
Step-by-step explanation:
Individuals experience potassium toxicity, known as hyperkalemia, under conditions of excessive potassium intake which can come from diet or certain medical conditions. Hyperkalemia impairs the function of skeletal muscles, the nervous system, and the heart. The symptoms of hyperkalemia include malaise, cardiac arrhythmias, mental confusion, numbness, weakness of respiratory muscles, and potentially fatal cardiac outcomes such as the heart "seizing" and stopping to pump blood. This happens because of high concentrations of potassium in the extracellular fluid (ECF) leading to partial depolarization of cells which can prevent normal relaxation and repolarization of the heart after a contraction.
An extreme intake of potassium, such as an injection of a potassium solution, is lethally disruptive because it dissipates the electrochemical gradient in cardiac muscle cells, preventing them from contracting efficiently. Such situations can often be fatal within minutes. Potential causes of potassium loss leading to hypokalemia include starvation, vomiting, diarrhea, or alkalosis, which can result in slow heart rate, muscle weakness, and irritability among others.