Final answer:
Fibrillation describes small areas of the myocardium contracting chaotically in the heart. An ectopic focus or ectopic pacemaker can lead to fibrillation, and it can be caused by various factors such as drug exposure and elevated stimulation by the nervous system.
Step-by-step explanation:
Fibrillation is the correct term to describe small areas of the myocardium contracting chaotically. Fibrillation is an uncoordinated beating of the heart and can occur in different parts of the heart, such as atrial fibrillation or ventricular fibrillation.
An ectopic focus or ectopic pacemaker, which can be stimulated by various factors, may lead to fibrillation.
Examples of diseases or pathological conditions that can lead to fibrillation include exposure to drugs like caffeine, digitalis, or acetylcholine, and elevated stimulation by both sympathetic or parasympathetic divisions of the autonomic nervous system.