HLSC 2410 Fall 2023 Cardiovascular Physiology PDF

HLSC 2410 Fall 2023 Cardiovascular (CV) Physiology: Overall Design & Introduction to Hemodynamics ( study of the flow of blood through the CV system) Assigned Reading: Vander’s Physiology Chapter 12 , Section A 15th Ed Chapter 12, 12.1-12.3 16th Ed Friday, Sept 7, 9:00 AM Dr. Maureen Basha mbash1@l...

HLSC 2410 Fall 2023 Cardiovascular (CV) Physiology: Overall Design & Introduction to Hemodynamics ( study of the flow of blood through the CV system) Assigned Reading: Vander’s Physiology Chapter 12 , Section A 15th Ed Chapter 12, 12.1-12.3 16th Ed Friday, Sept 7, 9:00 AM Dr. Maureen Basha [email protected] Overview of Block 2 • Intro to CV and Hemodynamics • Blood with a focus on Red Blood Cells and Hemostasis • Heart: Electrical and Mechanical events of the Heart. • Blood Vessels: Structure and Function of different types of blood vessels. • Regulation of Arterial Blood Pressure Learning Objectives A Describe the organization and function of the cardiovascular system. B Review the pathway of blood through the heart. Compare and contrast the pulmonary and systemic circulation. Define Bulk flow and pressure gradient and describe how changes in pressure gradients influence blood flow. Apply your understanding of Poiseuille’s Law to explain the factors that influence resistance to blood flow. Apply your understanding of Ohm’s Law to explain the relationship between flow, pressure and resistance in the cardiovascular system. Learning Objective 1: A. Describe the organization and function of the cardiovascular system. B. Review the pathway of blood through the heart. CV System Functions PRIMARY FUNCTION: Delivery of oxygenated, nutrient rich blood to meet metabolic needs of tissues of the body, removal of waste products of metabolism from tissues of body. This function involves a team effort of the CV and respiratory system Other functions: • Thermoregulation: regulation of skin blood flow to alter how much heat is lost/preserved from the surface of the body • Hormone production : production of hormones that regulate blood pressure • Fluid balance: exchange of fluids at capillaries to regulate body fluid balance CV system: Components Heart - Pump : generate pressure to drive blood through the vasculature and perfuse capillaries (site of gas/nutrient exchange) Heart wall :CARDIAC MUSCLE Vasculature- Tubing: specialized structure according to function of types of blood vessels Arteries- blood delivery to tissues Capillaries – oxygen/nutrient exchange with tissues Veins- return blood to heart Blood vessel wall: SMOOTH MUSCLE Blood-Medium: carry oxygen/nutrients to tissues and remove carbon dioxide/waste products • RBCs are key players in oxygen delivery • Platelets are key players in preventing blood loss Review: Heart Chambers and Valves Fig 12.9 Atria: “receiving” chambers • right - receives blood from vena cavae • left - receives blood from pulmonary veins Atrio-ventricular (AV) Valves: between atria and ventricles • right : tricuspid valve • left: bicuspid (mitral) valve Ventricles: “ pumping” chambers • right - pumps blood into pulmonary arteries • left - pumps blood into aorta Semilunar valves: Between ventricles and vasculature • right: pulmonary valve • left: aortic valve Purpose of one-way valves in the heart ➢ONE-WAY flow of blood through the heart and out into the vasculature. • INTO Atria → OUT of Ventricle ➢maintaining adequate filling and emptying of ventricles Heat valves are opened and closed by pressure differences between the two cardiovascular structures they are located. 8 Learning Objective 2: Compare and contrast the pulmonary and systemic circulation. Important Terminology • Blood Volume: Total amount of blood in the cardiovascular system (Liters) • Stroke Volume: amount of blood ejected from the ventricle with each beat (milliliters) • Heart Rate: number of times the heart beats per unit time (beats/minute) • Cardiac Output: amount of blood ejected from the ventricle per unit time. (volume/minute, i.e. Liters/minute) • Venous Return: amount of blood returned to the right atrium per unit time . (volume/minute, i.e. Liters/minute) Cardiovascular Circuit Mammalian Heart :”Double Pump” • Left Heart/ Systemic Circulation: Pumps oxygenated to body to meet cells metabolic needs. • Right Heart/Pulmonary Circulation: Pumps deoxygenated blood to lungs to pick up more oxygen RIGHT LEFT Deoxygenated blood: blood that has had some oxygen removed . This doesn’t mean blood has zero oxygen, it means less oxygen. Pulmonary versus systemic circulation Pulmonary Circulation: RIGHT • Low RT LT Pressure System: right heart only has to pump blood through the lungs •Low Resistance System: less extensive system of blood vessels to pump blood through Systemic Circulation: LEFT CLOSED SYSTEM • High Pressure System: left heart needs to pump blood to entire body • High Resistance System: extensive blood vessel circuitry to pump blood through Fig 12-5 Series Circuits : flow through tubes that are arranged sequentially Tube 1 Tube 2 Tube 3 Flow the same through each tube VR ~ 5 Liters/min Right atrium ALL of the blood vessels of the Systemic vasculature Right ventricle CO ~ 5 Liters/minute ALL of the blood the vessels of Pulmonary vasculature CO ~ 5 Liters/minute Left ventricle Left atrium Systemic Circulation in series with pulmonary circulation in a closed system • • • all blood from left side delivered to right side and vice versa Cardiac output (CO) of left heart is equal to the cardiac output of the right heart! Venous Return to the right heart is equal to Cardiac Output Parallel Circuits: flow through parallel arrangement of tubes Flow is delivered to tubes that branch off a single tube and is distributed amongst the branches Tube 1 Tube 2 Tube 3 Tube 4’[ Systemic Circulation: parallel branches off aorta to each organ system brain heart A o r t a skin skeletal muscle kidney gastrointestinal other Blood delivery to each organ system can be changed by changing diameter of blood vessels to each individual organ…stay tuned! Systemic Circulation: distribution of blood flow to systemic organs ➢Numbers represent % cardiac output at rest. • Greatest percentage of cardiac output delivered to abdominal organs as it is a large organ system • Heart receives small percentage, a relatively small organ. • Kidney receives a high percentage despite being relatively small as it has the job of filtering blood. • Skeletal muscle receives a high percentage as it is a large amount of tissue. • Although skin a large organ, it receives a relatively low percentage as it has low metabolic needs. • Blood flow into the brain remains virtually the same no matter what! Fig 12-6 Learning Objective 3: A. Define bulk flow and pressure gradient and describe how changes in pressure gradients influence blood flow. . Important Terminology: Pressure, Flow & Resistance ➢Pressure (mmHg): A FORCE • force exerted against something such , i.e. fluid exerting force against the wall of a container. ➢Flow (Liters/min): A RATE • volume of fluid that moves per unit time. ➢Resistance (mmHg/ml/min):A FORCE • force that opposes flow, i.e. a more viscous fluid would have more resistance to flow BLOOD PRESSURE Blood Pressure: force exerted on walls of blood vessels by blood inside it. Measured in mmHg (millimeters of mercury) • Arterial blood pressure: pressure in systemic arteries. • Pulmonary arterial blood pressure: pressure in pulmonary arteries Arterial blood pressure can be changed by: • Changing total blood volume • Changing rate of blood delivery into and rate of blood exit out of arteries Key regulated variable in the cardiovascular system is arterial blood pressure! Blood movement throughout the cardiovascular system: BULK FLOW • Bulk Flow: Movement of a fluid due to a pressure difference/pressure gradient. • Blood moves from a region of HIGH pressure to LOW pressure. • The pressure gradient to drive blood flow through the CV system is created by the pumping action of the heart. Pressure Gradient: pressure difference between two points Fig 12-7 P1 – P2 = ∆ P (pressure difference) • pressure difference between two points is the driving force for flow • Fluid moves from region of HIGH to LOW pressure. Learning Objective 4: Apply your understanding of Poiseuille’s Law to explain the factors that influence resistance to blood flow. Resistance and Poiseuille’s Law • Poiseuille’s (Pwaa-Zuh-EE) Law R = 8Lη / π • R = resistance • L = length of vessel 4 r This formula for understanding factors that influence resistance, not for calculating a value. • η = viscosity of blood • r = radius of vessel • Viscosity (η) –friction between molecules of flowing fluid Can you think of situations that would change blood viscosity? 22 R = 8L 4 πr Resistance is inversely proportional to radius TO THE FOURTH POWER The RADIUS of blood vessels is the most important determinant of the resistance to blood flow!!!!!! Effect of Tube Radius on Resistance Fig 12-8 Smaller radius tube has higher resistance : more fluid in contact with the walls of the tube and therefore more friction to work against to move blood. Physiological Significance: the radius of blood vessels can be changed by contracting or relaxing VASCULAR SMOOTH MUSCLE in the walls of blood vessels. Change radius of blood vessels: change resistance Changing resistance of blood vessels: Vasoconstriction: Contraction of SMOOTH muscle in blood vessel wall to reduce radius of blood vessel (r) • What happens to resistance? • What happens to flow for any given pressure gradient? Vasodilation: Relaxation of SMOOTH muscle in blood vessel wall to increase radius of blood vessel (r) • What happens to resistance? • What happens to flow for any given pressure gradient? R = resistance r = radius Learning Objective 5 Apply your understanding of Ohm’s Law to explain the relationship between flow, pressure and resistance in the cardiovascular system. Ohm’s Law: Flow of blood is equal to the pressure gradient divided by the resistance. F=∆P/R Flow = Pressure Gradient Resistance Flow: directly proportional to Δ P - Flow increases as pressure gradient increases P1 This formula for understanding factors that influence resistance, not for calculating a value. P2 - Flow decreases as pressure gradient decreases Flow: inversely proportional to resistance (R) - Flow increases as resistance DECREASES - Flow decreases as resistance INCREASES F = P-pressure; F-flow; R-resistance P1 – P2 R Effect of Tube Radius on Fluid Flow: Parallel Circuit F = Δ P/R P • Tube A and B have the same pressure gradient (∆ P) • radius of Tube A two times greater than tube B • flow (mL/min) through tube A is 16 times more than through tube B. Fig 12-8 Blood takes the path of least resistance when blood vessels are arranged in parallel to each other: i.e. more blood to organs with dilated blood vessels, less blood to organs with constricted blood vessels Summary: Key figures and formulae R = 8Lη / πr4 • Changing radius of blood vessels major determinant of resistance Pulmonary Circulation: low pressure low resistance circuit Systemic Circulation: high pressure high resistance circuit • Blood flow increases with increases in pressure gradient and decreases with increases in resistance