Respuesta :
Answer: The upper chamber is called an atrium, or auricle, and the lower chamber is called a ventricle. The two atria act as receiving chambers for blood entering the heart; the more muscular ventricles pump the blood out of the heart.
Answer:
The pumping of the heart involves the alternate contraction and relaxation of the chambers of the heart. The upper chambers of the heart are called atria , and the lower chambers of the heart are called ventricles .