heart

• the heart contracts to pump blood around the body
• valves make sure blood flows in the right direction
• blood flows into the two atria from the vena cava and the pulmonary vein
• atria contracts pushing the blood into the ventricles
• ventricles contract forcing blood into the pulmonary artery and the aorta and out the heart
• blood then flows to the organ through arteries and returns through veins
• the atria fill again to start cycle over
• resting heart rate is controlled by a group of cells that act as a pacemaker
• pacemaker cells produce a small electric impulse which spread to the muscle cells causing them to contract
• an artificial pacemaker is used to control heartbeat if natural pacemaker doesnt work
• an artificial pacemaker is a device placed under your skin and has a wire going to your heart