PSL301H Cardiovascular System Lecture Notes 2022 PDF

CARDIOVASCULAR SYSTEM (PSL301H) 2022 - 8 lectures Lecture Title 1 The Heart: Cardiac Muscle and Action Potential 2 Cardiac Excitability: Heart Rate and ECG 3 The Heart as a Pump: Cardiac Cycle 4 Regulation of Cardiac Output, Blood vessel Introduction 5 Blood flow: Pressure gradients and r...

CARDIOVASCULAR SYSTEM (PSL301H) 2022 - 8 lectures Lecture Title 1 The Heart: Cardiac Muscle and Action Potential 2 Cardiac Excitability: Heart Rate and ECG 3 The Heart as a Pump: Cardiac Cycle 4 Regulation of Cardiac Output, Blood vessel Introduction 5 Blood flow: Pressure gradients and resistance 6 Blood Pressure Control 7 Microvasculature, Lymph and Venous Return 8 Cardiovascular Health and Disease Silverthorn Textbook Chapter 14: Cardiovascular Physiology Chapter 15: Blood flow and control of blood pressure Professor Scott Heximer Physiology, 661 University Avenue, Rm 1414 E-mail: [email protected] About these lectures Goals: To understand: • (1) the basic science of the heart and blood vessels • (2) how dysfunction leads to disease To achieve this: • Learn the anatomy and physiology of the cardiovascular system • Understand: muscle biochemistry • Consider: Heart as a pump in closed system • Understand: pressure/ volume/ flow/ resistance PSL301H – Lecture 1: The heart: cardiac muscle and cardiac action potential What are the main functions of the CIRCULATORY SYSTEM? ‘What’ is being transported and ‘where’? Describe the structures of the heart and cardiac muscle How does an electrical signaling lead to contraction? **Please review my action potential review video Silverthorn 7th ed: 443-452, 435-439, 8th ed: 440-449, 432-436 What are the main functions of the “CIRCULATORY SYSTEM”? 1. Transport and distribute essential substances to the tissues. 2. Remove metabolic byproducts. 3. Adjustment of oxygen and nutrient supply in different physiologic states. 4. Regulation of body temperature. 5. ‘Humoral’ communication. Cardiovascular system anatomy The cardiovascular system is a closed loop with two pumps working in series. The heart contains two pumps working simultaneously to circulate blood through the system. Arteries take blood away from the heart, and veins carry blood back to the heart. Pulmonary Circuit: Right ventricle ! pulmonary trunk ! pulmonary arteries (branches) ! lungs pulmonary veins return O2-rich blood to the left atrium. Systemic Circuit: Left ventricle !Aorta carrying O2rich blood from the left ventricle! branches with an artery to each organ. Arteries divide into arterioles and capillaries which then lead to venules. Structure of the Heart • The heart is composed mostly of myocardium (muscle) 2 pumps – need muscle to squeeze STRUCTURE OF THE HEART Aorta Pulmonary artery Superior vena cava Pericardium Right atrium Auricle of left atrium Coronary artery and vein BASE Right ventricle Diaphragm (e) The heart is encased within a membranous fluid-filled sac, the pericardium. Left ventricle APEX (f) The ventricles occupy the bulk of the heart. The arteries and veins all attach to the base of the heart. The Cardiovascular System • The Heart has 4 Valves to direct one-way blood flow • Bicuspid (mitral) valve. • Tricuspid valve. • Pulmonary valve. • Aortic valve. " Semilunar valves " cup-like leaflets, found at ventricular exit points " Pulmonary valve – between RV and pulmonary trunk " Aortic valve – between LV and aorta " Atrioventricular valves " found between the atria and ventricles " tricuspid valve on the right AV junction " bicuspid (mitral) valve on the left AV junction " valves are re-enforced by chordae tendinae attached to muscular projections within the ventricles. Copyright © 2009 Pearson Education, Inc. Anatomy of the Heart: Major vessels, input and output Aorta Right pulmonary arteries Superior vena cava Right atrium Pulmonary semilunar valve Left pulmonary arteries Left pulmonary veins Left atrium Cusp of the AV (bicuspid) valve Cusp of a right AV (tricuspid) valve Chordae tendineae Papillary muscles Left ventricle Right ventricle Inferior vena cava Descending aorta • The heart valves ensure one-way flow Passage of Blood Through the Heart Blood follows this sequence through the heart: → superior and inferior vena cava → right atrium → tricuspid (AV) valve → right ventricle → pulmonary (semilunar) valve → pulmonary trunk and arteries to the lungs → pulmonary veins leaving the lungs → left atrium → bicuspid (AV/mitral) valve → left ventricle → aortic (semilunar) valve → aorta → to the body. Path of blood through the heart and body Review question: A red blood cell is just leaving the foot. Arrange the following structures in the order that the red blood cell will encounter them on its path if it travels once around the body back to the foot. 1) Inferior vena cava 2) Mitral valve 3) Pulmonary artery 4) Aorta 5) Pulmonary semilunar valve Coronary artery circulation Cardiac Muscle: Central piece in CV physiology Myocardial muscle cells are branched, have a single nucleus, and are attached to each other by specialized junctions known as intercalated disks. Intercalated disks Myocardial muscle cell Intercalated disk (sectioned) Nucleus Intercalated disk Mitochondria Cardiac muscle cell Contractile fibers Unique properties of cardiac muscle Cardiac Muscle Properties •Syncytial network – branched myocyte connections (1 cell may be connected to several –think about waves of dominoes) •Connected by intercalated disks containing desmosomes (VelcroTM) to allow force transfer, and gap junctions for electrical connectivity •Mitochondria occupy one-third of cell volume A schematic diagram of a cardiac muscle shows T-tubules, sarcoplasmic reticulum and myofilaments in skeletal muscle D. M. Bers, Excitation-Contraction Coupling and Cardiac Contractile Force, 2nd ed. (2002) Cardiac Muscle: Excitation-contraction coupling 10 Ca2+ 1 ECF 3 2 K+ ATP ICF Na+ 9 Ca2+ 1 Action potential enters from adjacent cell. NCX 3 Na+ RyR 2 Ca2+ 2+ 2+ 3 Ca induces Ca release through ryanodine receptor-channels (RyR). 2 3 SR L-type Ca2+ channel Ca2+ 4 2+ Ca sparks Sarcoplasmic reticulum (SR) 2+ Ca stores release causes 4 Local 2+ Ca spark. ATP T-tubule Voltage-gated Ca2+ channels open. Ca2+ enters cell. 2+ 5 Summed Ca sparks create a Ca2+ signal. 8 2+ 6 Ca ions bind to troponin to initiate contraction. 5 Ca2+ signal 6 Contraction Ca2+ 7 Relaxation occurs when Ca2+ unbinds from troponin. Ca2+ 7 7 Relaxation Actin Myosin 2+ 8 Ca is pumped back into the sarcoplasmic reticulum for storage. 2+ 9 Ca is exchanged with Na+ by the NCX antiporter. 10 Na+ gradient is maintained by the Na+-K+-ATPase. Side view of Ca2+-dependent regulation of acto-myosin interaction in cardiac muscle Copyright © 2009 Pearson Education, Inc. Action Potentials transmit electrical signals in the heart Copyright © 2009 Pearson Education, Inc. ke upstro (mV) resting potential -90 1 ms Number of open channels • Downstroke phase: Na+ permeability decreases as Na+ channels inactivate. K permeability increases as K+ channels open. Membrane potential approaches EK 0 ENa ok e n s tr • Upstroke phase: Na+ permeability increases as Na+ channels open. Membrane potential approaches ENa +61 d ow Ion channels alter membrane permeability EK Membrane hyperpolarized Na+ channels K+ channels Action Potentials propagate through the heart tissue Propagation: Rest Stimulated (local depolarization) Propagation (current spread) • Na+ channel open generates local depolarization • Local depolarization activates adjacent Na+ channels… and so on… Copyright © 2009 Pearson Education, Inc. Cardiac action potentials are unique • Cardiac muscle action potentials differ considerably from action potentials found in neural and skeletal muscle cells. • Main difference • Main difference is duration: • Nerves, about 1 ms. • Skeletal muscle cells, 2-5 ms. • Cardiac action potentials range from 200 to 400 ms. Membrane potential (mV) Myocardial Contractile Cell Action Potential 1 +20 PX = Permeability to ion X PNa 2 PK and PCa 0 –20 3 –40 0 –60 PNa –80 4 PK and PCa 4 –100 0 Phase 100 200 Time (msec) 300 Membrane channels 0 Na+ channels open 1 Na+ channels close 2 Ca2+ channels open; fast K+ channels close 3 Ca2+ channels close; slow K+ channels open 4 Resting potential Myocardial Contractile Cells: Refractory period • Refractory period in cardiac muscle Skeletal Contractile Cells: Refractory period • Refractory period in skeletal muscle Figure 14-14 - Overview Cardiac Na+ channels : inactivation and resetting upon repolarization n io de po la ri za t t za ri la po re io n Closed/Primed by repolarized state Inactivation open Copyright © 2009 Pearson Education, Inc. Inactivated by depolarized state Shown are the action potential (red) and muscle contraction profiles (blue) for skeletal and cardiac muscle in response to an electrical stimulus at time 0 ms (black arrowhead). If you give a second stimulus 50 ms after the first (red arrowhead), when would you expect the next action potential to begin for the two different muscle cells. Skeletal A. Skeletal, 50 ms; Cardiac, 50 ms. C. Skeletal, Never; Cardiac, 50 ms E. Skeletal, 50 ms; Cardiac, 300 ms Cardiac B. Skeletal, 100 ms; Cardiac, 300 ms D. Skeletal, 50 ms; Cardiac, Never Action Potentials in Skeletal muscle vs Myocardium One down – seven to go #