The Cardiovascular System Overview

The Cardiovascular System

• The heart is a muscular organ that pumps blood through the body, it is part of the cardiovascular system.
• Blood circulates through the body using two distinct systems: the pulmonary circulation and the systemic circulation.
• The pulmonary circulation routes blood from the heart to the lungs to pick up oxygen and releases carbon dioxide.
• The systemic circulation pumps oxygenated blood from the heart throughout the body and returns deoxygenated blood to the heart.

Functions of the Heart

• The heart generates blood pressure.
• The heart routes blood through the body.
• The heart ensures one-way flow of blood.
• The heart regulates the supply of blood to tissues.

Heart Characteristics

• The heart is about the size of a fist and weighs less than a pound.
• Cardiac muscle cells contract when stimulated by action potentials.
• Action potentials of cardiac muscle cells are longer than action potentials of skeletal muscle cells.

Conduction System of Heart

• The conduction system of the heart is composed of specialized muscle cells that coordinate atrial and ventricular contractions.
• Cells in the conduction system can produce spontaneous action potentials.
• The conduction system includes: the sinoatrial node, atrioventricular node, atrioventricular bundle, right and left bundle branches, and Purkinje fibers.

Cardiac Cycle

• The cardiac cycle includes: atrial systole, ventricular systole, atrial diastole, and ventricular diastole.
• Heart sounds are produced by the closing of heart valves.
• The 'lubb' sound is caused by closure of the atrioventricular valves.
• The 'dupp' sound is caused by closure of the semilunar valves.

Regulation of Heart Function

• Stroke volume is the volume of blood pumped per ventricle per contraction, roughly 70 milliliters per beat.
• Heart rate is the number of heart beats per minute, approximately 72 beats per minute.
• Cardiac output is the volume of blood pumped by a ventricle in 1 minute, roughly 5 liters/minute.
• Cardiac output is calculated by multiplying stroke volume times heart rate.

Intrinsic Regulation of the Heart

• Intrinsic regulation refers to the heart's control of its own cardiac output.
• Venous return is the amount of blood returning to the heart.
• Preload is the degree of ventricular wall stretch at the end of diastole.
• Preload, venous return, and stroke volume are linked.
• Starling’s law of the heart explains the relationship between preload and stroke volume.
• Afterload is the pressure against which ventricles must pump blood.

Extrinsic Regulation of Heart

• Extrinsic regulation uses external mechanisms, like the nervous and chemical systems, to control heart function.
• The autonomic nervous system controls heart activity through the sympathetic and parasympathetic divisions.
• The baroreceptor reflex regulates heart function by monitoring blood pressure.
• The chemoreceptor reflex regulates heart function by sensing chemical changes in the blood.

Heart Disease

• Coronary artery disease occurs when blood supply to the heart muscle is decreased due to narrowed coronary arteries.
• Myocardial infarction or heart attack occurs when one or more coronary arteries close, causing cardiac muscle lacking blood supply to die and scar.

Heart Procedures

• Angioplasty is a procedure used to open blocked blood vessels.
• Stents are inserted to keep vessels open.
• A bypass procedure reroutes blood away from blocked arteries.