Anatomy & Physiology/Cardiovascular System

About the size of a an adult fistHollow and cone shapedWeighs less than a pound

Sits atop the diaphragm and is centered between the left and right lung.

The pointed apex is directed towards the left hip, while the base is directed towards the right shoulder.

The heart is composed of four chambers:The right and left atria, which make up the top

portion of the heart, are receiving chambers.The right and left ventricles, which make up

the bottom portion of the heart, are the discharging and pumping chambers.

The lengthwise membrane that divides the heart is referred to as the interatrial septum OR interventricular septum, depending on which chambers it is dividing.

The heart functions as a double pump.Pump #1 controls

pulmonary circulation, which brings blood to and from the lungs.

Pump #2 controls systemic circulation, which carries blood throughout the body and back to the heart.

Superior and Inferior Vena Cava = located above and below the right atrium, carry deoxygenated blood from the body into the right atrium of the heart.

Pulmonary Arteries = Exit from the right ventricle and carry deoxygenated blood from the heart to the lungs.

Pulmonary Veins = Exit the lungs and carry oxygenated blood to the left atrium of the heart.

Aorta (Artery) = Exits the left ventricle of the heart and carries oxygenated blood to the body tissues.

Coronary Arteries = branch out from the aorta and deliver oxygenated blood to the heart tissues.

Cardiac Veins = carry deoxygenated blood from the heart tissues to the right atrium.

The heart has four valves, which allow blood to flow in only one direction through the heart:Atrioventricular (AV) Valves = located between

the atrial and ventricular chambers on each side. These valves prevent backflow into the atria when the ventricles contract.The left atrioventricular valve is also called the

bicuspid valve because it is made of two flaps.The right atrioventricular valve is also called

the tricuspid valve because it is made of three flaps.

The heart has four valves, which allow blood to flow in only one direction through the heart:Semilunar Valves = located between the

ventricles and the large arteries that exit them. These valves prevent backflow into the ventricles when the ventricles relax.Pulmonary semilunar valves = located

between right ventricle and pulmonary arteries.

Aortic semilunar valves = located between left ventricle and aorta.

Systole = heart contractionDiastole = heart relaxationThese terms refer to the contraction and

relaxation of the ventricles, unless otherwise noted.

Blood Pressure readings are recorded as systolic pressure over diastolic pressure, which refer to the pressure in the arteries during contraction and relaxation, respectively.

A typical blood pressure reading is around 120/80 mmHg

Unlike skeletal muscle, cardiac muscle can contract independently, even if it is severed from all nerve connections.

Two systems act to regulate heart activity:The nerves of the nervous system act to

decrease and increase heart rate in response to environmental changes.

The intrinsic conduction system (nodal system) built into the cardiac muscle tissue.

There are four major parts that make up the intrinsic conduction system:Sinoatrial (SA) Node = tissue located on the

right atrium which starts each heartbeat and sets the pace for the whole heart. Also known as the pacemaker.

Atrioventricular (AV) Node = tissue located at the junction of the atria and ventricles.

Atrioventricular (AV) Bundle = groups of fibers located on the interventricular spetum.

Purkinje Fibers = spread throughout the muscle of the ventricle walls.

The electrochemical impulse that travels through the heart and generates each heart beat follows this path:The impulse is generated in the SA NodeThe impulse travels through the right and left

atrium, triggering contraction of the atria.The impulse reaches the AV Node where it is

delayed long enough for the atria to complete contraction.

The impulse then travels along the Bundle of His to the Purkinje fibers and begins contraction of the ventricles at the apex of the heart.

The impulses generated by the heart can be detected on the surface of the body.

A typical EKG includes three waves:P Wave = the first wave, which signals the

depolarization of the atriaQRS Complex = signals the depolarization of

the ventriclesT Wave = the second wave, signals the

repolarization of the ventricles.