The Heart

Tricuspid Bicuspid Right SV Left SV Valves of the Heart A-V valves Semilunar valves Tricuspid Bicuspid Right SV Left SV bw RA - bw LA - bw RV - bw LV and RV and LV and and pulmonary aorta artery

The Structure of the Heart

The Heartbeat Cycle DIASTOLE SYSTOLE 2. Atria contract. 3.Ventricles contract. Semilunar valves are open. 1. Heart is relaxed. AV valves are open.

Systole: Contraction period The Heartbeat Cycle The pumping action of the heart has two periods: Systole: Contraction period Diastole: Relaxation period During diastole the heart muscle is relaxed and A-V valves are open. Blood flows from the atria into ventricles . (This fills the ventricles %70 not fully.)

The Heartbeat Cycle Systole begins with the contraction of atria. When atria contract they can pass all blood inside to the ventricles, so ventricles are full of blood. Then ventricles contract and the pressure of contraction closes A-V valves. The pressure also opens the semilunar valves. As a result blood flows from right ventricle to pulmonary artery and transported to lungs; blood in the left ventricle flows into the aorta to be carried throughout the body.

Heart Sounds Heart sounds are formed as a result of opening and closing of A-V and semilunar valves. They are called the lub-dup sounds. lub-dup sound closing of closing of A-V valves semilunar valves

Heart Sounds Lub sound: Dup sound: Ventricles contract Pressure increases Mitral and tricuspid valves close Dup sound: At the beginning of diastole pressure in the relaxed ventricles drops below that in the arteries Semilunar valves close

Heart Sounds Lub hiss dup When A-V valves don’t close completely (blood flows back into atria causes this sound) Lub dup hiss When semilunar valves don’t close completely (blood flowing back into ventricle causes this sound)

The Coronary Arteries They are the first arteries to branch off from the aorta. They nourish the heart muscle. If there is blood clot or accumulation of materials in coronary arteries this may cause heart attack.

The Coronary Arteries

Heart Rate The number of times the heart contracts each minute is the heart rate or pulse rate. (The pulse is the expansion and relaxation that can be felt in an artery each time the left ventricle contracts and relaxes.) It is measured by feeling the impact of blood on the wall of an artery. Pulse can be felt in wrist on each side of throat Normal heart rate 50-80 (beats) times in a minute In vigorous exercise 200 times a minute

Control of the Heartbeat Heart is made up of the cardiac muscle. Although the nervous system controls the contraction of other types of muscle, cardiac muscle has a built-in ability to contract. Even when it is removed ftom the body, the heart will keep beating for a while in a special solution called Ringer solution. Ringer solution contains NaCl, KCl and CaCl.

Control of the Heartbeat There are structures in the heart muscle which are called nodes. Sinoatrial node (SA node = pacemaker): is located in the wall of the right atrium near the opening of superior vena cava. Atrioventricular node (AV node): is located in the wall of right atrium near the septum (behind the tricuspid valve)

Control of the Heartbeat

Control of the Heartbeat SA node generates impulses, specialized fibers carry impulses throughout the atria and stimulates AV node. The group of fibers called bundle of His distribute the impulses through the ventricles from AV node.

Control of the Heartbeat Contraction of the heart begins when, the heart receives electrical impulses from the SA node atria contract the impulse reaches the AV node the AV node triggers an impulse that causes the ventricles to contract Bundle of His conducts the impulses through the ventricles.

Control of the Heartbeat SA node . . The electrical current produced by heart can be recorded by a machine that produces an electrocardiogram (ECG). . AV node Bundle of His

The Rate of Heart Beat is Regulated by Vagus nerve Slow down the pacemaker Cardioaccelerator nerve Speed up the pacemaker Acetylcholine Vagus nerve [CO2] in blood High temperature Anxiety Adrenalin Cardiovascular nerve decreases the heartbeat rate increases the heartbeat rate

Cardiac Output The amount of blood pumped by the left ventricle each minute is called cardiac output. Resting: the heart pumps about 5 lt. of blood each minute. Exercise: cardiac output may increase up to 37 lt. per minute.