E109 Lecture 9: CV 1 Fall 2024 Cardiovascular System PDF

E109 Lecture 9: CV 1 Volume, Pressure, Valves Learning objectives Observe that the cardiovascular system includes the heart, the systemic and pulmonary circuits Understand that changes in volume induce changes in pressure to drive flow through the circulatory system...

E109 Lecture 9: CV 1 Volume, Pressure, Valves Learning objectives Observe that the cardiovascular system includes the heart, the systemic and pulmonary circuits Understand that changes in volume induce changes in pressure to drive flow through the circulatory system Learn that unidirectional flow through the heart is achieved through the opening and closing of heart valves Integrate that the blood output with each heartbeat (stroke volume) depends on the filling (end diastolic volume) and emptying (end systolic volume) of the ventricles Function of the Cardiovascular System Transport Regulation Respiratory Hormonal Transport of O2 &CO2 Endocrine organs Target cells minimizediffusion of gasses Nutritive Temperature Digestive Tract/Liver All cells Blood diversion for Thermoregulation Excretory Immune Wastes Liver/Kidneys Transport of Leukocytes, Cytokines Heart as a Pump Pulmonaryarteries lungs 25/8 comingfromtheheartis goingtowardstheheartis mm veinsgobackto theheart d d L oxigenated nomatterwhatsystem veins arenotalways depend I system theyrein 120/80 veinsruntotheheartin both insystemiccircitiinParents deoxygenated inthe pulmonary circutveinsareoxygenated arteries goawayfrom thebody Structure of the Heart Aorta Superior Pulmonary vena cava artery Left atrium Right start atrium Coronary artery and vein Right ventricle Left ventricle tissue toa takingb9 theyare cells The sides are reversed because we are looking at a mirror image Pumps and Valves V P whenvolumedecreases Pressureincreases P causes liquidtomove Contraction (Systole) ax V P V P P P Relaxation (Diastole) Relaxation (Diastole) Valves and Cardiac Cycle AV valves Pulmonary vein 9m arteryinto Semilunar leftatrium valves Ventricles relaxed Ventricles contracted diastole systole The Cardiac Cycle 1 Late diastole—both sets of chambers are relaxed and START ventricles fill passively. 5 Isovolumic ventricular relaxation—as ventricles relax, pressure in ventricles falls, blood flows back into 2 Atrial systole—atrial contraction cusps of semilunar valves and snaps them closed. forces additional blood into ventricles. S1 S2 4 Ventricular ejection— 3 Isovolumic ventricular as ventricular pressure contraction—first phase of rises and exceeds pressure ventricular contraction pushes AV in the arteries, the semilunar valves closed but does not create valves open and blood is enough pressure to open semilunar ejected. valves. Pressure-Volume relationship during cardiac cycle Time (msec) closing of the AV valves 0 100 200 300 400 500 600 700 800 120 A AV valves close C 90 Dicrotic notch B Semilunar valves open Pressure B (mm Hg) Left main p.at 60 ventricular pressure C Semilunar valves close D AV valves open 30 Left atrial pressure D iiaT ventricl 0 A Heart abouttopush 9 fd volume sounds S1 S2 135 E E End diastolic Left ventricular volume (mL) F afterallbloodis pushedout 65 Atrial Ventricular Ventricular Atrial F End systolic volume systole systole diastole systole EDV-ESV= stroke volume volumewitheach beat of Atrial systole Isovolumic ventricular Ventricular systole Early ventricular Late ventricular Atrial systole theheart contraction diastole diastole Review The cardiovascular system includes the heart, the systemic and pulmonary circuits Changes in volume induce changes in pressure to drive flow through the circulatory system Unidirectional flow through the heart is achieved through the opening and closing of heart valves The output of blood with each heartbeat (stroke volume) depends on the filling (end diastolic volume) and emptying (end systolic volume) of the ventricles during a cardiac cycle Cardiac Muscle Contraction Two Types of Cardiac Muscle Cells contractilecells autorhythmiccells Membrane potential of autorhythmic cell Membrane potential of contractile cell Autorhythmic Cells Yielita inraeiin Contractile cell Intercalated disk with gap junctions Myocardial Contractile Cells: Structure iii iii havesacromeres Cardiac muscle cell Intercalated disk (sectioned) Nucleus Intercalated disk Mitochondria givingcellssomething toattachto to contract Contractile speed Myocardial Contractile Cells: Action Potentials 1 Resting potential east +20 3 PNaEmirates 4 tii t.in irsstor 2 Na+ channels open PK PCa datingtennis it Membrane Potential (mV) 0 3 Na+ inactivation gate tostay high closes -20 4 Ca2+ channels open fast K+ channels close potassium9PMcloses -40 5 2 depolarization PK PCa 5 Ca2+ channels close -60 by Na slow K+ channels open PNa -80 1 1 nohyperpolaritations -100 lower membrane 0 100 200 300 Time (ms) of antibody Refractory Period: Skeletal Muscle youcannotgetsummation b process is refractory period its going as fast as it can Refractory Period: Cardiac Muscle there is no summationof force in cardiac muscles Cardiac Muscle Contraction 10 9 1 Action potential enters 3 Na+ Ca2+ from adjacent cell. Ca2+ 2 K+ ECF 1 ATP NCX Voltage-gated Ca2+ 2 ICF channels open. Ca2+ 3 Na+ enters cell. Ca2+ RyR2 2+ 2+ 2 3 Ca induces Ca release through ryanodine 3 receptor-channels (RyR2). SR L-type Sarcoplasmic reticulum Ca2+ (SR) Ca2+ channel 4 Local release causes Ca2+ stores Ca2+ spark. 4 ATP 2+ 5 Summed Ca2+ sparks 8 create a Ca signal. Ca2+ sparks T-tubule 2+ 6 Ca ions bind to troponin 5 to initiate contraction. Ca2+ signal Ca2+ Ca2+ 7 Relaxation occurs when Ca2+ unbinds from troponin. 6 7 7 Actin 2+ 8 Ca is pumped back into the sarcoplasmic reticulum for storage. 2+ 9 Ca is exchanged with Na+ by the NCX antiporter. Contraction Relaxation Myosin 10 Na+ gradient is maintained by the Na+-K+-ATPase. Review Contractile cells within the heart are connected through intercalated disks that contain gap junctions and allow for transmission of force and graded potentials between cells Action potentials of cardiac contractile cells are long lasting with the cell remaining depolarized for substantially longer period of time The long refractory period prevent summation of force The contraction cycle within cardiac muscle has features that resemble both skeletal and smooth muscle contraction Two Types of Cardiac Muscle Cells Membrane potential of autorhythmic cell Membrane potential of contractile cell Autorhythmic Cells Contractile cell Intercalated disk with gap junctions Figure 14-17 Action potential: Autorhythmic Cells pacemaker occurs natural there is noretractionperiod 20 3 1 If channels open Na+ enters cells 2 Ca2+ channels open causing 0 rapid depolarization 3 Ca2+ channels close K+ channels 4 open mm –20 a ntal 4 K+ moves out of the cell 2 5 If channels open Na+ enters cells Threshold –40 1 5 –60 Pacemaker Action potential potential Time Electrical Conduction in the Heart 1 1 SA node depolarizes. SA node AV node THE CONDUCTING SYSTEM OF THE HEART SA node Internodal pathways AV node AV bundle Bundle branches Purkinje fibers Figure 14-18, step 1 Electrical Conduction in the Heart 1 1 SA node depolarizes. SA node AV node 2 2 Electrical activity goes rapidly to AV node via internodal pathways. THE CONDUCTING SYSTEM OF THE HEART SA node Internodal pathways AV node AV bundle Bundle branches Purkinje fibers Figure 14-18, steps 1–2 Electrical Conduction in the Heart 1 1 SA node depolarizes. SA node AV node 2 2 Electrical activity goes rapidly to AV node via internodal pathways. 3 Depolarization spreads more slowly across THE CONDUCTING SYSTEM atria. Conduction slows through AV node. OF THE HEART SA node 3 Internodal pathways AV node AV bundle Bundle branches Purkinje fibers Figure 14-18, steps 1–3 Electrical Conduction in the Heart 1 1 SA node depolarizes. SA node AV node 2 2 Electrical activity goes rapidly to AV node via internodal pathways. 3 Depolarization spreads more slowly across THE CONDUCTING SYSTEM atria. Conduction slows through AV node. OF THE HEART 4 Depolarization moves SA node rapidly through ventricular 3 conducting system to the Internodal apex of the heart. pathways AV node AV bundle 4 Bundle branches Purkinje fibers Figure 14-18, steps 1–4 Electrical Conduction in the Heart 1 1 SA node depolarizes. SA node AV node 2 2 Electrical activity goes rapidly to AV node via internodal pathways. 3 Depolarization spreads more slowly across THE CONDUCTING SYSTEM atria. Conduction slows through AV node. OF THE HEART 4 Depolarization moves SA node rapidly through ventricular 3 conducting system to the Internodal apex of the heart. pathways 5 Depolarization wave spreads upward from the apex. AV node AV bundle 4 Bundle branches Purkinje fibers 5 Figure 14-18, steps 1–5