A deficiency in which electrolyte results in muscle weakness, polyuria, and U waves on an ECG?

A deficiency in potassium is associated with muscle weakness, polyuria, and the presence of U waves on an ECG. Potassium plays a crucial role in maintaining cellular function, particularly in muscle and nerve cells. When potassium levels are low, it can lead to disturbances in electrical conduction in the heart and skeletal muscle, resulting in clinical manifestations such as muscle weakness and increased urinary output due to impaired renal handling of electrolytes.

The U wave observed on the ECG, which appears after the T wave, can be indicative of hypokalemia (low potassium levels). This is a hallmark finding that helps differentiate potassium deficiency from other electrolyte imbalances. The cardiovascular effects of hypokalemia include not only U waves but also an increased risk of arrhythmias and changes in heart rhythm, which further highlight the importance of adequate potassium levels for normal heart function.

In contrast, deficiencies in sodium, chloride, or calcium present with different clinical symptoms and do not specifically lead to the combination of muscle weakness, polyuria, and U waves on an ECG. Sodium deficiency (hyponatremia) typically presents with neurological symptoms due to cerebral edema, chloride deficiency may not have specific clinical manifestations, and calcium deficiency can lead to muscle cramps and tetany but would not produce U waves