Final answer:
Ectopic foci in Afib and atrial flutter originate from areas of the heart other than the SA node and are known as ectopic pacemakers or foci. They can be stimulated by factors such as localized ischemia, drugs, autonomic nervous system stimulation, or disease conditions.
Step-by-step explanation:
The ectopic foci in atrial fibrillation (Afib) and atrial flutter originate from areas of the heart other than the SA node. These areas, known as ectopic foci or ectopic pacemakers, can be a part of the conduction system or other contractile cells. They are stimulated by factors such as localized ischemia, certain drugs, elevated stimulation from the autonomic nervous system, or various disease conditions.