Exam # 3 Study Guide MPP 3202 1st EditionChapter 14: Cardiovascular SystemComponents of the Cardiovascular System:• Heart = pumps oxygenated blood to body and deoxygenated blood to lungs• Blood vessels = arteries, arterioles, capillaries, post-capillaries, venules, veins (pulmonary/systemic)• Blood = plasma, RBC’s and WBC’sMain Functions of the Cardiovascular System:1. To transport materials throughout the body2. To protect the body from infection and blood loss3. To help the body maintain a constant temperature4. To help maintain fluid balancePressure Differentials Direct Blood Flow:• Pressure created by contracting muscles is transferred to blood• Driving pressure is created by the ventricles• If blood vessels dilate, blood pressure decreases• If blood vessels constrict, blood pressure increases• Volume changes affect blood pressure in cardiovascular system• Flow through a tube is directly proportional to the pressure gradient (the higher the pressure gradient the greater the flow, must be positive)• Flow through a tube is inversely proportional to resistance (if resistance increases flow decreases)Poiseuille’s Law:• Resistance is proportional to length (L) of the tube (blood vessel)◦ Resistance increases as length increases• Resistance is proportional to viscosity (), or thickness, of the fluid (blood)◦ Resistance increases as viscosity increases • Resistance is inversely proportional to tube radius to the fourth power◦ Resistance decreases as radius increases Resistance Opposes Flow:• Small change in radius has a large effect on resistance to blood flow◦ Vasoconstriction is a decrease in blood vessel diameter/radius anddecreases blood flow◦ Vasodilation is an increase in blood vessel diameter/radius and increases blood flow• Flow = P/R◦ Flow of blood in the cardiovascular system is▪ Directly proportional to the pressure gradient▪ Inversely proportional to the resistance to flow Cardiac Muscle:• Myocardium = cardiac muscle• The heart generates pressure when it contracts (systole) and pumps blood into the arterial or the circulation• Arteries act as a pressure reservoir during diastole• Mean arterial pressure = cardiac output - peripheral resistanceThe Heart:• Pericardium = tough membranous sac that encases the heart• Chordae tendineae = attach flaps of valves to the walls of the ventricles• Papillary muscle = extensions of ventricle muscle that hold the chordae in place• Left ventricle = receives blood from left atrium, sends blood to body • Right ventricle = receives blood from right atrium, sends blood to lungs• Left atrium = receives blood from pulmonary veins, sends blood to left ventricle• Right atrium = receives blood from vena cavae, sends blood to right ventricle• Aorta = receives blood from left ventricle, sends blood to systemic arteries• Superior/inferior vena cava = receives blood from systemic veins, sends toright atrium• Pulmonary artery = receives blood from right ventricle, sends to lungs• Pulmonary veins = receives blood from lungs, sends to left atrium • Coronary artery/veins = surface blood vesselsHeart Valves:• Two sets of heart valves ensure one-way flow◦ Atrioventricular valves▪ Between atria and ventricles▪ Tricuspid valve on the right side▪ Bicuspid valve, or mitral valve, on the left side◦ Semilunar valves▪ Between right ventricle and pulmonary trunk = Pulmonaryvalve▪ Between left ventricle and aorta = Aortic valveVentricular Contraction & Relaxation:• During ventricular contraction, the AV valves remain closed to prevent blood flow backward into the atria• The semilunar valves prevent blood that has entered the arteries from flowing back into the ventricles during ventricular relaxationCardiac Muscle:• Contractile cells◦ Striated fibers organized into sarcomeres• Autorhythmic cells, or pacemakers◦ Signal for contraction◦ Smaller and fewer contractile fibers compared to contractile cells◦ Do not have organized sarcomeres• Myocardial muscle cells ◦ are branched◦ have a single nucleus◦ are attached to each other by specialized junctions known as intercalated disks• The spiral arrangement of ventricular muscle allows ventricular contraction to squeeze the blood upward from the apex of the heart• Intercalated disks contain desmosomes that transfer force from cell to cell, and gap junctions that allow electrical signals to pass rapidly from cell to cellExcitation-Contraction Coupling:1. Action potential enters from adjacent cell. 2. Voltage-gated Ca2 channels open. Ca2 enters cell. 3. Ca2 induces Ca2 release through ryanodine receptor-channels (RyR). 4. Local release causes Ca2 spark.5. Summed Ca2 sparks create a Ca2 signal.6. Ca2 ions bind to troponin to initiate contraction.7. Relaxation occurs when Ca2 unbinds from troponin.8. Ca2 is pumped back into the sarcoplasmic reticulum for storage. 9. Ca2 is exchanged with Na by the NCX antiporter.10. Na gradient is maintained by the NA-K-ATPase.Cardiac Muscle Contraction:• Force generated is proportional to number of active crossbridges◦ Determined by how much Ca2 is bound to troponin• Sarcomere length affects force of contraction• The refractory period lasts almost as long as the entire muscle twitch◦ Long refractory period in a cardiac muscle prevents tetanusCardiac Autorhythmic Cells :• Autorhythmic cells have unstable membrane potentials called pacemaker potentials• The pacemaker potential gradually becomes less negative until it reaches threshold, triggering an action potentialElectrical Conduction of Myocardial Cells:• Autorhythmic cells spontaneously fire action potentials• Depolarizations of the autorhythmic cells then spread rapidly to adjacent contractile cells through gap junctions 1. SA node depolarizes2. Electrical activity goes rapidly to AV node via internodal pathways3. Depolarization spreads more slowly across atria. Conduction slows through AV node4. Depolarization moves rapidly through ventricular conducting system to the apex of the heart5. Depolarization wave spreads upward from the apex• Atrioventricular (AV) node◦ Routes the direction of electrical signals so the heart contracts from apex to base◦ AV node delay is accomplished by slower conduction signals through nodal cells• Sinoatrial (SA) node◦ Sets the pace of the heartbeat at 70 bpm◦ AV node (50 bpm) and Purkinje fibers (25–40 bpm) can act as pacemakers under some