Cardiovascular Physiology PDF

Cardiovascular Physiology “…For it is the heart by whose virtue and pulse the blood is moved, perfected, made apt to nourish and is preserved from corruption and coagulation…It is indeed the fountain of life, the source of all action.”...

Cardiovascular Physiology “…For it is the heart by whose virtue and pulse the blood is moved, perfected, made apt to nourish and is preserved from corruption and coagulation…It is indeed the fountain of life, the source of all action.” Joe Sepe, PhD -William Harvey, Exercitatio de Motu Cordis (1628) CV 1 October 7th, 2024 Session Learning Objectives: Students will be able to: 1. Describe the roles of the cardiovascular system in maintaining homeostasis. 2. Identify the components of the cardiovascular system. 3. Compare and contrast the structure of the pulmonary and systemic circulatory systems. 4. Define Ohm’s Law and relate it to flow in the cardiovascular system. 5. Recall the factors that impact resistance to flow, with importance placed on vessel radius. 6. Recall the major anatomical structures of the heart and order of blood flow through the heart and vasculature. 7. Describe the electrical connection of cardiac myocytes. 8. Compare and contrast cardiac, skeletal, and smooth muscle cells. Office Hours Mondays: 2-3pm, room 3-129 in Jackson Hall Wednesdays: 230-330pm in lab classroom The Cardiovascular System Roles in Homeostasis: Main transport system for delivering nutrients, removing wastes, distributing hormones and other signaling molecules Temperature regulation Recall from Unit 1 what life would be like for a cell at the center of a mass of 75 trillions cells if it depended on diffusion… To be “biologically viable”, most cells in the body are within 10 µm of a capillary Components of the Cardiovascular System Heart: the biological pump; generates force to move the blood. 2 events for each beat: electrical (action potential) followed by mechanical (contraction) Blood: the medium through which O2 and nutrients are transported. Vasculature: the vessels through which the blood flows; they are NOT passive in the process of blood movement. Let’s take a tour through each of these components  The Blood Total volume of blood, on average, is 5.5 liters Plasma averages 55-58% of total blood volume, and is part of the extracellular fluid (ECF) “buffy coat” : contains leukocytes (immune cells) and platelets (clotting). Erythrocyte (red blood cells) volume averages 42- (hematocrit = 45%) 45%, called the “hematocrit”. Mainly for gas transport. Overview of Heart and Vasculature 2 pumps (right ventricle (RV) and left ventricle (LV)) and 2 circulatory systems (pulmonary and systemic) Parallel vascular beds vs vascular beds in-series Pressure differences between pulmonary and systemic circuits Perfusion: passage of blood through a vascular bed Ischemia: lack of oxygen/blood flow. Typically due to an occlusion. The left and right sides of the heart are not identical Size Really Can Make a Difference Wall of left ventricle (the myocardium, i.e. the muscle) is much thicker than the right. Allows the LV to generate greater pressure. Why does the LV need to generate more force (pressure) than the RV? The pressure in the systemic circulation is much higher than the pressure in the pulmonary circulation. The ventricles must generate enough pressure to create a gradient so that blood can flow (from high pressure to low pressure). Parallel vs Series Arrangement of Vascular Beds Pulmonary circuit is arranged in-series, systemic is in-parallel. Same quality of blood to all tissues Allows for better regulation of blood flow Takes less pressure than if arranged in series Guyton, Figure 14.1 Receptors of the CV system Targets for therapeutic modification Muscarinic Acetylcholine Receptor (mAChR) Cholinergic at Nicotinic Acetylcholine located hR Receptor (nAChR) nAC tonomic all au a li gang Alpha (α) Adrenergic (we’ll focus on α1) Beta (β) (we’ll focus on β1 and β2) Raff, Fig. 19-1 Pressure, Flow, and Resistance F (or Q) = Flow (L/min) This is not velocity (distance/time) ∆P = Pressure difference between two points (mmHg). It’s the gradient that matters, not the absolute pressures. R = Resistance to flow (mmHg*min/L) It’s the Pressure Gradient! Same rate of flow, despite differences in absolute pressure (assuming same resistance) However, having to generate higher pressures to create this gradient, and the high pressures the organs experience, can cause pathologies. Resistance Resistance = Flow What impacts resistance? L = vessel length = viscosity of the blood r = radius of vessel (raised to the 4th power) Changes in vessel radius can have drastic impacts on resistance and flow A B C The Heart: Our Biological Pump Heart Valves Purpose: To promote one-way direction of blood flow. When they don’t function properly, disease typically ensues. 2 types (4 valves total): 1) Atrioventricular valves (AV) right AV (tricuspid) left AV (bicuspid) 2) Semilunar valves (SL) pulmonary semilunar valve aortic semilunar valve Pressure gradients induce opening and closing of valves (a passive process; valves don’t directly require ATP to open/close) Atrioventricular (AV) Valves Right AV valve = tricuspid valve Left AV valve = bicuspid valve; mitral valve Semilunar Valves Pulmonary and Aortic Semilunar Valves Innermost layer of the heart. Separates chambers from the heart muscle (myocardium) Thick layer of cardiac muscle Fluid filled sac that surrounds the heart, protecting it and providing lubrication. Epicardium separate the myocardium from the pericardial fluid.  Electrical connections between cardiac muscle cells (coordination of the heart beat) “Adhesive” that holds the neighboring cells together Electrical synapse Connected via gap junctions = rapid communication! Functional syncytium (heart muscle cells are synchronized in health) Cardiac Myocytes Striated Mostly mononucleated (one nucleus) Branched ends Cardiac Muscle Compared to Skeletal and Smooth All three types: Sliding filaments and cross-bridges ATP powers the force generation Elevated Ca2+ triggers contraction Ways cardiac is similar to skeletal: Ways cardiac is similar to smooth: Has sarcomeres Pacemaker cells Striated Gap junctions (syncytium) Has troponin Ca2+ entry from ECF T-tubules Autonomic/hormones modulate activity Involuntary