Animal Systems II: Cardiovascular Physiology VEM 5111G PDF

Animal Systems II: Cardiovascular Physiology VEM 5111G  Animal Systems II: Cardiovascular Physiology VEM 5111G Course coordinator: Carl Hansen, PhD Office: V2-163 Phone: Email: [email protected] Office hours by appointment (made via hansenc@...

Animal Systems II: Cardiovascular Physiology VEM 5111G  Animal Systems II: Cardiovascular Physiology VEM 5111G Course coordinator: Carl Hansen, PhD Office: V2-163 Phone: Email: [email protected] Office hours by appointment (made via [email protected]) All course materials on e-learning E-learning site Syllabus, Calendar, and notes for each lecture Power points will be posted before lecture Links to supplemental websites to visit Link to physiology textbook in Syllabus/course materials Copies of the PHYSIOLOGY textbooks in VET library Animal Systems II: Cardiovascular Physiology Seven Modules: Module 1: Introduction to the Cardiovascular System Module 2: Electrical Activity of the Heart Module 3: Cardiac Contractility, Cardiac Cycle, and Cardiac Output Module 4: ECG Analysis and Interpretation Module 5: Histology and Development Module 6: The Circulation Module 7: System Control & Integration Schedule Cardiovascular Function and Control: Dr. Hansen Clinical ECG (electrocardiography): Dr. Aherne ECG in clinical skills lab: Dr. Aherne Practical application/measurement/discussion Cardiovascular Histology lecture and lab: Dr. Pierezan Cardiovascular Embryology and Development: Dr. Tevosian  Course Grading Grading (see Syllabus): ECG lab attendance & participation: 5% of total grade. Four Canvas-based quizzes: 10% of total grade One final exam: 85% of total grade Clinical correlate questions are included on final exam An Introduction To The Cardiovascular System Learning Objectives Identify the basic components of the cardiovascular system and how they are integrated. Identify the relationship between pressure and flow in the cardiovascular system. Cardiovascular Disease Statistics Estimated 1 in 4 Americans will develop cardiovascular disease. Estimated 1 in 3 dogs have some form of heart disease by age 13. Cardiovascular disease is often without any obvious symptoms prior to becoming a severe problem. The main function of the cardiovascular system is to continuously distribute blood throughout the body providing nutrient delivery and waste removal. It consists of two divisions Systemic and Pulmonary Flow is unidirectional Has the capacity to adjust its outflow to meet the demands of the tissues. Key measure of cardiac performance is Cardiac Output: The volume of blood pumped per unit time (L/min) Humans: 5 L/min Dogs: 2.5 L/min Other functions of the cardiovascular system? Each Division Consists of Four Functional Components: 1. Pump Left and right ventricles 2. Distribution system Arterial tree Systemic arteries Pulmonary arteries 3. Exchange region Capillaries Systemic capillaries Pulmonary capillaries 4. Collection system Venous tree Atria during ventricular systole (ventricles contracting) The Heart Produces the Energy for Blood to Flow through the Cardiovascular System What is the function of the heart? What causes blood to flow? Anatomically one structure. Physiologically two separate pumps Each pump consists of an atrium and a ventricle. Both pumps are mechanically and electrically interdependent. Uni-directional flow is maintained by valves At ventricular input: Mitral and tricuspid valves (AV valves) prevent backflow into atria and venous system when ventricles are generating pressure (contracting). At ventricular output: Aortic and pulmonic semilunar valves prevent backflow of high pressure aortic and pulmonary trunk blood back into the relaxing ventricles.  Heart valves open and close passively based on the direction of the pressure gradients. Isovolumetric Ventricular filling Fluid ejection contraction Diastole Systole Relaxation phase Contraction phase Aortic > ventricular pressure Ejection when Aortic < ventricular pressure Left atrium > left ventricle P Left atrium < left ventricle pressure Valve status ? Ventricle fully relaxed Left AV? ____________ Aortic semilunar? ___________ Isovolumetric contraction Left AV? ____________ Aortic semilunar? ___________ Ventricle ejecting blood Left AV? ____________ Aortic semilunar? ___________ The left pump generates higher pressure than the right pump Pressure: application of a force onto a surface. Pressure: amount of force acting on a unit area. mmHg, torr, psi, pascals Flow: movement of a fluid down a pressure gradient Why does the left heart generate higher pressures than the right heart? Resistance is the force opposing flow. It is caused by friction and deflection forces generated as the fluid flows through the vessels and results in a decrease (loss) in pressure. Significance: Pressure decreases as the fluid flows over distance The systemic (left) pump must generate greater pressure than the pulmonary (right) pump in order to provide flow through the larger surface area and higher resistance of the systemic cardiovascular tree relative to the pulmonary cardiovascular tree The much larger mass of the left ventricle is indicative of its ability to generate around 5 times greater pressure than the right ventricle. Three key factors that affect resistance (that dissipate pressure) to flow: Viscosity of the fluid (blood) (h) Length of the vessel (l) Diameter of the vessels (r) Poiseuille's law Q= flow Basic features of the vascular system or distribution system Function: Transports metabolic substrates to tissues and removes metabolic waste products from tissues. Arteries supply high pressure blood flow to all major regions of the body. Have robust, elastic muscular walls. Arterioles regulate perfusion pressure to tissue capillary beds. Have thick, less elastic muscular walls. Regulate blood pressure through vasoconstriction and vasodilation. Precapillary sphincters regulate blood flow through capillary beds. Exchange occurs at the level of the capillaries. Very thin. Composed only of a single layer of endothelial cells. No muscular wall, typically porous (leaky) cell junctions. What us the function of the lymphatic system with regards to capillary exchange? Venules and veins collect blood from the capillaries and transport it back to the heart Vein/venules also serve as the blood’s “reservoir” system Venules and veins are thin-walled, highly compliant, low-pressure vessels. Provides a large blood store capacity that can be quickly recruited to the arterial side via venoconstriction.  Cardiovascular Regulation Maintains blood pressure Adjusts cardiac output to the demands of the tissues. Functional coordination is regulated by Intrinsic cardiovascular mechanisms: Frank-Starling Law of the heart. Myogenic vascular smooth muscle. Autonomic nervous system Sympathetic. Parasympathetic. Hormonal regulation RAAS (renal angiotensin system) Vasopressin (antidiuretic hormone) Epinephrine Atrial natriuretic protein Cardiovascular disease: Failure to adequately deliver nutrients and O2, and adequately remove metabolic wastes and CO2 from tissues. Cardiac pathologies: Pump dysfunction: Valve failure Myocardium dysfunction Conduction perturbations Vascular dysfunction atherosclerosis hypertension embolisms ischemic attacks hemorrhage All can lead to a disruption of perfusion (flow) to the tissues. Valve dysfunction is a common veterinary problem Flow no longer unidirectional What is a common cardiac sign indicating improper unidirectional flow? FLOW Flow = the volume of blood that moves past a particular point in the cardiovascular system at a given time. Cardiac output: volume of blood pumped per minute by the heart This would be the flow entering the ascending aorta. “Typical” canine: cardiac output is _____________. “Typical” human: cardiac output is _____________. Remember: Flow rate is determined by the pressure pushing the liquid and resistance in the system countering flow. Flow (Q) of a liquid is described by Poiseuille's law: (laminar flow) Which side of the heart, left or right, pumps the most blood (generates the greatest flow)? Relationship between pressure and flow Blood pressure (BP): Measurement of the cardiac force being generated to cause the blood to flow. A However, the rate of flow is proportional to the pressure B gradient (DP) between two points, and not the absolute pressure generated at the heart. C Can simplify Poiseuille's law to: Q=DP/R All the above vessels have the same (Flow = pressure gradient/ resistance) resistance. = DP/R (R=8hl/pr4) Which vessel above has the lowest flow rate? Do any of the vessels have the same For a human: flow rate? 93 Average aortic BP?_________ mmHg (120/80) ~2 mmHg Average vena cava BP? ______ The driving force (DP)?______ mmHg Resistance decreases flow Poiseuille's law: = DP/R (R=8hl/pr4) Simple frictional forces in the system impede flow. Length (l): physiologically, changes little. Viscosity (h): physiologically relatively constant, but can become a pathological issue (polycythemia (high hematocrit) or hyperproteinemia) Diameter (r): Greatest determinant of flow because = r4 Physiologically, the primary regulator of cardiovascular resistance Doubling the diameter increases flow 16 fold Halving diameter decreases flow 16 fold. Hence: blood pressure and tissue perfusion is primarily regulated by vasodilation and vasoconstriction First measurement to determine blood pressure was done in a horse by Reverend Stephen Hales in 1733. Sphygmomanometer  SUMMARY Heart is a two-pump system consisting of systemic and pulmonary circuits. The heart generates the pressure which provides the driving force for flow through the cardiovascular system. Valves within the heart ensure unidirectional flow. Flow = the amount of fluid passing through a point in the system per unit time (L/min) Blood flow can be described by Poiseuille's law: Q=(P1-P2)/R = DP/R Two primary determinants of blood flow are: 1. DP: Magnitude of the pressure gradient 2. R: Resistance in the system to flow Strongest contributor to flow resistance in the cardiovascular system is vessel diameter, since is contribution is to the 4th power (r4). Length is relatively constant Viscosity is relatively constant, but is influenced by hematocrit and blood protein levels