Deoxygenated blood pumped from right ventricle via pulmonary artery to lungs. Explore this web site to learn about the cardiovascular system. Be certain to look at the Table of Contents. Describe two in the human body. Describe cardiac muscle.
Heart sounds caused by closing of valves.
They can contract without a signal from the nervous system. However, contractions of cardiac muscle cells must be coordinated. The tissue of the SA node has characteristics of both muscle and nervous tissue. It contracts like muscle and generates electrical impulses. As the SA node contracts a wave of excitement travels through the heart muscle causing the two atria to contract in unison.