Final answer:
The triad of pheochromocytoma includes episodic headaches, diaphoresis, and tachycardia. It results from excessive production of catecholamines by tumors in the adrenal medulla, particularly epinephrine and norepinephrine, causing hypertension and potential arrhythmias.
Step-by-step explanation:
The triad of pheochromocytoma refers to the classic presentation of symptoms which include episodic headaches, diaphoresis (excessive sweating), and tachycardia (rapid heartbeat). Pheochromocytomas are tumors that arise from chromaffin cells in the adrenal medulla, leading to the excessive production of catecholamines, namely epinephrine and norepinephrine. These hormones play a critical role in the body's fight-or-flight response, and their overproduction results in a variety of symptoms, the most significant of which is hypertension (high blood pressure).
Due to the catecholamine release, patients may experience increased heart rate and blood pressure. In some cases, catecholamine release can be massive, which coupled with sympathetic stimulation, may cause heart rhythm abnormalities (arrhythmias). However, there is no parasympathetic stimulation to the adrenal medulla to counteract these effects.
Furthermore, excessive catecholamines affect ion channels, particularly increasing the influx of sodium and calcium ions that can lead to heightened depolarization rates and a shortened repolarization period in cardiac cells. This abnormal ion movement contributes to the cardiovascular disturbances in pheochromocytoma.