Cardiovascular System

• The closed circulatory system of vertebrates is known as the cardiovascular system
• Blood circulates to and from the heart through arteries, veins, and capillaries
• Arteries carry blood away from the heart to organs throughout the body
• Arteries branch into arterioles within organs, which then convey blood to capillaries
• Capillaries are microscopic vessels with thin, porous walls that allow rapid transfer of substances between cells and blood
• Veins return blood to the heart with lower pressure compared to arteries
• Arteries transport blood swiftly and at high pressure to tissues
• Veins have thinner walls with fewer elastic fibers and muscle fibers compared to arteries
• Double circulation involves two circuits in the cardiovascular system, with the heart serving as the pump for both
• The heart contracts and relaxes in a rhythmic cycle known as the cardiac cycle
• The sinoatrial (SAN) node, or pacemaker, initiates the heartbeat and can be influenced by hormonal and nervous stimuli
• The conducting system of the heart includes the atrioventricular (AV) node, bundle of His, and Purkinje fibers
• The SA node generates electrical impulses that spread through the heart, causing muscle contractions
• Control of the cardiac cycle involves a combination of nervous and hormonal mechanisms, with the sympathetic system speeding up the pacemaker and the parasympathetic system slowing it down
• The cardiovascular control centers in the medulla oblongata of the brain regulate the activity of nerves affecting the pacemaker
• Body temperature can also influence the heart rate
• Arteriosclerosis involves the thickening of artery walls due to plaque deposits
• Coronary Heart Disease occurs when the coronary arteries are blocked, leading to insufficient blood supply to the heart and potentially causing a heart attack
• Oxygenated blood then returns to the left side of the heart through pulmonary veins.
• Blood flows from the right side to the lungs where it picks up oxygen.
• The heart is divided into four chambers, two atria (right and left) and two ventricles (right and left).
• Valve closure prevents backflow during contraction.
• In the lungs, carbon dioxide diffuses out of the bloodstream and oxygen enters the bloodstream.
• Valve closure creates sounds that can be heard with a stethoscope.
• Blood flows from the right ventricle to the lungs via the pulmonary trunk (pulmonary artery).
• Semilunar valves prevent backflow between the ventricles and the great vessels.
• Systole refers to the period of time when the heart contracts.
• Ventricular systole contracts and ejects blood out of the heart.
• Ventricular diastole occurs when both ventricles relax simultaneously.
• The left atrium receives deoxygenated blood from the body through four pulmonary veins.