Dysrhythmias are a sign of potassium depletion in cardiac muscles. Other cardiovascular effects include irregular, rapid, weak pulse; decreased blood pressure; flattened and inverted T waves, prominent U waves, depressed ST segments, peaked P waves, and prolonged QT intervals. Muscle weakness is a symptom of potassium depletion in skeletal muscles; potassium facilitates the conduction of nerve impulses and muscle activity. Irritability, as a result of heightened neuromuscular activity, is a sign of hyperkalemia. Abdominal cramps, as a result of heightened neuromuscular activity, is a symptom of hyperkalemia. Tingling of the fingertips, as a result of a lowered threshold of excitation of peripheral sensory nerve fibers, is a symptom of hypocalcemia.