The Cardiovascular System

Functions Transportation What is transported? Vehicle? The force?

Anatomy of the Heart Location Hollow, cone-shaped Size? Weighs?

Anatomy(cont.) How stay in place? The walls of the heart are composed of three layers Epicardium Myocardium Endocardium

4 Chambers of the Heart Two superior Atria Receiving chambers low pressure Two inferior Ventricles Thick walled discharging chambers pumps of the heart

Pulmonary Circuit Pump The circulation of the right side of the heart to the lungs and back to the left side of the heart Carries blood to the lungs for gas exchange and then return it to the heart.

Systemic Circulation Supplies oxygen and nutrient-rich blood to all body organs. From the left side of the heart through the aorta to the body tissues and back to the right side of the heart.

Valves Four valves, which allow blood flow in only one direction through the heart AV valves prevent backflow back into the atria as ventricles contract Bicuspid (Mitral)-the left AV valve Tricuspid-the right AV valve AV valves are open during heart relaxation and closed when ventricles are contracting

Valves (cont.) Semilunar valves guard the bases of the two large arteries leaving the ventricular chambers Pulmonary valve-guards the right ventricle from backflow from the pulmonary arteries Aortic valve-guard the left ventricle from backflow of the aorta Semilunar valves are closed during heart relaxation and are forced open when the ventricles contract. Chordae tendineae anchor the cusps to the walls of the ventricles

Blood Vessels Blood circulates inside the blood vessels, which form a closed transport system. As the heart beats, blood is propelled into the large arteries leaving the heart. It then moves into successively smaller and smaller arteries and then into the arterioles, which feed the capillary beds in the tissues.

Blood vessels (cont.) Capillary beds are drained by venules, which in turn empty into veins that finally empty into the great veins entering the heart. Arteries carry blood away from the heart Veins drain body tissue and return blood to the heart. Capillary beds where exchanges occur.

Cardiac Cycle Atria contract simultaneously,as they start to relax, contraction of the ventricles begins. Systole means contraction of the ventricles Diastole means relaxation of the ventricles The first heart sound (lub) is caused by the closing of the AV valves The second sound (dup) occurs when the semilunar valves close at the end of systole

Heart Sounds (cont.) Blood flows silently if it is smooth and uninterrupted. Abnormal heart sounds are called murmurs.

Cardiac Circulation Coronary arteries (not the blood in the heart) supply oxygen and nourishment to the heart These arteries are compressed when ventricles are contracting and fill when the heart is relaxed. (why would a rapidly beating heart caused a problem?)

Physiology of the Heart In one day the heart pushes the body’s supply of 6 quarts or so of blood through the blood vessels over 1000 times. As the heart beats, the blood makes continuous round trips-in and out of the heart, through the rest of the body, and then back to the heart-only to be sent out again.

Conduction of the Heart Cardiac muscle cells contract spontaneously. Atrial and ventricular cells beat at different rates if left alone, so they need a controlling system to regulate heart activity. Nervous system Nodal system built into heart tissue

Nodal System SA node (sinoatrial) in the right atrium starts each heartbeat and sets the pace for the whole heart. Called the pacemaker SA node- AV node-AV bundles-bundle branches-Purkinje fibers resulting in a wringing contraction

Heart Rate (cont.) Heart rate is also modified by various chemicals, hormones, and ions. Epinephrine and thyroxine both increase heart rate Electrolyte imbalances pose a real threat to the heart. Reduced levels of ionic Ca in the blood depress the heart and hypercalcemia causes prolonged contractions that the heart may stop.

Physiology of Circulation A person’s arterial pulse and blood pressure measurements are a good indication of the efficiency of their circulatory system. Pulse is the alternating expansion and recoil of an artery that occurs with each beat of the left ventricle creates a pressure wave that travels through the entire arterial system. Normally pulse equals the heart rate. ( beats per minute)

Cardiac Cycle Refers to the events of one complete heartbeat, during which both atria and ventricles contract and then relax. The average heart beats about 75 times per minute. Length of cardiac cycle is about.8 seconds

Measuring Blood Pressure Because the heart alternately contracts and relaxes, the off-and-on flow of blood into the arteries causes the blood pressure to rise and fall during each beat. So two arterial blood pressure measurements are usually made Systolic pressure-pressure in the arteries at the peak of ventricular contraction Diastolic pressure-pressure when the ventricles are relaxing