CARDIOVASCULAR SYSTEM
Overview Heart and Vessels 2 Major Divisions Pulmonary Circuit Systemic Circuit Closed and Continuous Loop
Location Aorta Superior vena cava Right lung Pulmonary trunk Base of heart Parietal pleura (cut) Pericardial sac (cut) Apex of heart (c) Diaphragm
III. Structure Coverings Pericardium Parietal Pericardium Visceral Pericardium Pericardial Cavity Wall Epicardium Myocardium Endocardium
Fig. 19.3a Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pericardial cavity Myocardium Endocardium Epicardium Pericardial sac
Anatomy Chambers Atria Ventricles Septums Interatrial Interventricular Valves Atrioventricular Semilunar
Fig. 19.9 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10 1 Blood enters right atrium from superior and inferior venae cavae. Aorta 5 11 5 Left pulmonary artery 2 3 Blood in right atrium flows through right AV valve into right ventricle. Contraction of right ventricle forces pulmonary valve open. Superior vena cava Right pulmonary veins Right atrium Right AV (tricuspid) valve Right ventricle 6 1 2 9 3 4 8 7 6 Pulmonary trunk Left pulmonary veins Left atrium Aortic valve Left AV (bicuspid) valve Left ventricle 4 5 6 7 8 9 Blood flows through pulmonary valve into pulmonary trunk. Blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO 2 and loads O 2. Blood returns from lungs via pulmonary veins to left atrium. Blood in left atrium flows through left AV valve into left ventricle. Contraction of left ventricle (simultaneous with step 3 ) forces aortic valve open. Blood flows through aortic valve into ascending aorta. Inferior vena cava 11 10 Blood in aorta is distributed to every organ in the body, where it unloads O 2 and loads CO 2. 11 Blood returns to heart via venae cavae.
Cardiac Conduction System Sinoatrial Node (SA node) Atrial Ventricular Node (AV node) AV Bundle Bundle Branches Purkinje Fibers
Fig. 19.12 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 SA node fires. Right atrium Sinoatrial node (pacemaker) Atrioventricular node Atrioventricular bundle 2 1 3 2 4 5 Left atrium Purkinje fibers Bundle branches 2 3 4 5 Excitation spreads through atrial myocardium. AV node fires. Excitation spreads down AV bundle. Purkinje fibers distribute excitation through ventricular myocardium. Purkinje fibers
EKG (Electrocardiogram/ECG) P Wave QRS Wave T Wave
Millivolts Fig. 19.15b Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. R R +1 PQ segment ST segment P wave T wave 0 PR interval Q S QT interval QRS interval 1 Atria contract Ventricles contract Atria contract Ventricles contract
Action Potential Slight Difference in Action Potential An influx of Calcium causes a plateau. This plateau prolongs depolarization and allows for a stronger contraction. Also prolongs absolute refractory period.
Membrane potential (mv) Fig. 19.14 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 Plateau 1 Voltage-gated Na + channels open. +20 0 20 4 Action potential 5 Myocardial relaxation 2 3 Na + inflow depolarizes the membrane and triggers the opening of still more Na + channels, creating a positive feedback cycle and a rapidly rising membrane voltage. Na + channels close when the cell depolarizes, and the voltage peaks at nearly +30 mv. 40 60 80 2 1 Myocardial contraction Absolute refractory period 4 5 Ca 2+ entering through slow Ca 2+ channels prolongs depolarization of membrane, creating a plateau. Plateau falls slightly because of some K + leakage, but most K + channels remain closed until end of plateau. Ca 2+ channels close and Ca 2+ is transported out of cell. K + channels open, and rapid K + outflow returns membrane to its resting potential. 0.15.30 Time (sec)
Fig. 19.16 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Key Wave of depolarization Wave of repolarization R P P Q S 1 Atria begin depolarizing. 4 Ventricular depolarization complete. R P P T Q S 2 Atrial depolarization complete. 5 Ventricular repolarization begins at apex and progresses superiorly. R R P P T Q Q S 3 Ventricular depolarization begins at apex and progresses superiorly as atria repolarize. 6 Ventricular repolarization complete; heart is ready for the next cycle.
Cardiac Cycle Systole Diastole Cycle Atrial systole, Ventricular Diastole Atrial Diastole, Ventricular Systole Atrial Diastole, Ventricular Diastole
Fig. 19.19 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atrium Atrioventricular valve Ventricle (a) Atrioventricular valves open Atrioventricular valves closed Aorta Pulmonary artery Semilunar valve (b) Semilunar valves open Semilunar valves closed