THE HEART IS A HOLLOW, MUSCULAR ORGAN THAT CONTRACTS AT REGULAR INTERVALS, FORCING BLOOD THROUGH THE CIRCULATORY SYSTEM. The Heart is cone-shaped, about the size of a fist, and is located between the lungs directly behind the sternum. (breastbone). The heart is tilted so that the apex (the pointed end) is oriented to the left.

The heart is enclosed in a protective membrane sac called the pericardium. The pericardium surrounds the heart and secretes a fluid that reduces friction as the heart beats. Vertically dividing the right and left sides of the heart is a wall called the septum. The septum prevents the mixing of oxygen-poor and oxygen- rich blood. The Human Heart

RIGHT SIDE OF THE HEART Deoxygenated blood from the body enters the right side of the heart through 2 large blood vessels called:  superior vena cava  carries deoxygenated blood from the head and upper body to the right atrium.  Inferior vena cava  carries deoxygenated blood from all veins below the diaphragm to the right atrium. LEFT SIDE OF THE HEART Receives oxygenated blood from the lungs and pumps it to the cells of the body.

1. Pulmonary Circulatory System  blood carried to and from lungs. 2. Cardiac Circulatory System  blood travels through the heart tissue. 3. Systematic Circulatory System  blood travels to and from the body cells. Circulatory System

2 thin walled atria (atrium)  chambers of the heart that receive blood from veins. 2 thick walled ventricles  chambers of the heart that deliver blood to the arteries.

Cardiac Conduction When the heart relaxes (between beats), pressure in the circulatory system causes the atrium to fill with blood. When the heart contracts, blood is squeezed from the right atrium to the right ventricle through flaps of tissue called a atrioventricular (AV) valves  AV valves separate the atria from the ventricles, and maintain one-way flow. When the heart contracts a second time, blood in the right ventricle is sent through the semilunar valves and to the pulmonary arteries to the lungs.  Pulmonary Arteries are the only arteries to carry oxygen-poor blood.  Semilunar valve prevents blood from traveling back into the right ventricle.

Oxygen-rich blood leaves the lungs and returns to the heart by way of blood vessels called the pulmonary veins Pulmonary veins are the only veins to carry oxygen-rich blood. Returning blood enters the left atrium, it passes through the AV valve to the left ventricle. From the left ventricle, blood is pumped through the SL valve to the aorta artery that carries blood to every part of the body BUT the lungs. At the base of the aorta is a valve that prevents blood from flowing back into the left ventricle.

The aorta is the largest artery in the body, and carries oxygenated blood to the body. coronary arteries  a branch of the aorta, that carries blood (oxygen and nutrients) to the cardiac muscles. Pumping Animation

Fat deposits and plaques accumulate here. Operation involves removing the a vein from another patients body and grafting it into the position in the heart. However, to graft the vein, the heart needs to be stopped. Heart is cooled and a heart- lung machine maintains oxygen supply and blood flow to tissues. Coronary Bypass Surgery YouTube - Off Pump Coronary Artery Bypass - A Beating Heart Procedure YouTube - Off Pump Coronary Artery Bypass - A Beating Heart Procedure

A procedure where a small, thin, hallow tub, called a catheter, is passed into an artery in the groin. The catheter is pushed up through the aorta and into the heart. A dye that is visible in X-rays is then injected into the catheter. An area of restricted blood flow pinpoints the blockage. Angioplasty  balloon on the end of the catheter opens the blocked blood vessel. Blood sample tell info about oxygen present in different chambers

Appear striated (striped) Display a branching pattern Can contract without being stimulated by external nerves, myogenic muscle.  Explains why the heart will continue to beat when removed form the body. YouTube - beating Human heart

The heart contracts and relaxes in a rhythmic cycle. Contracts  pumps blood Relaxes  chambers fill with blood One complete cycle of pumping and filling is the cardiac cycle.

sinoatrial (SA) node  a small mass of tissue in the right atrium that sets the hearts beat rate at 70 beats per minute. The SA node acts as a pacemaker Contraction now travel to a second node: atrioventricular (AV) node  (right atrioventriculal region) This node is the conductor, passes impulses through the Purkinje Fibers, and on to the ventricles.  Purkinje fibers run along the septum that separates the right and left ventricles, to the bottom tip of the heart. From here, branch fibers carry impulses along the outer walls of the ventricles and back towards the atria.  Heart Beat Heart Beat

Sympathetic and parasympathetic nervous systems conduct impulses from the brain to the SA node. In stressful situations, the sympathetic stimulates an increase in heart rate (increased blood flow). During times of relaxation, parasympathetic nerves are stimulated to slow the heart rate.

Familiar heart sounds are caused by the closing of heart valves. When atria relax (diastole), it fills with blood and as blood increase the atria contracts; thereby, forcing AV valves to open. Blood flows from the atria to the ventricles. As ventricles fill with blood and then they contract (systole), which closes the AV valve. This creates the lub sound as blood in pushed into the arteries. To prevent blood in the arteries from re-entering the semilunar valves close. The closing of this valve creates the dup sound.

Occurs when valves do not close completely. Murmur created when blood leaks past the valve. Results in a faster beat rate (compensate for decreased oxygen delivery) and enlarged heart (atria receive additional blood from the ventricle).

Used to map electrical fields within the heart to make tracings to diagnosis certain heart problems. Changes in electrical current reveal normal or abnormal events. Examples of ECGs

P wave  the electrical impulse that causes atrial contraction. QRS wave  the electrical impulse that causes the ventricles to contract. T wave  signals that the ventricles are relaxed.

Irregular heart beats caused by a blocked coronary artery.

Beta blockers  helpful in patients with irregular heartbeats or who display high blood pressure. Receptor sites receive hormones that affect the way the cells behave. Epinephrine, a stress hormone, increases heart rate and narrowing blood vessels. Beta blockers attach and block this receptor.