Cardiovascular - Blood Pressure Students PDF

Cardiovascular System Blood Pressure 1 Learning Objectives Differentiate between systolic and diastolic blood pressure Describe the factors that influence BP Discuss real-life scenarios and their effect on BP 2...

Cardiovascular System Blood Pressure 1 Learning Objectives Differentiate between systolic and diastolic blood pressure Describe the factors that influence BP Discuss real-life scenarios and their effect on BP 2 1  Blood Pressure Pressure exerted by blood on walls of a vessel caused by contraction of the ventricles highest in aorta 120 mm Hg during systole / 80 during diastole Pressure falls steadily in systemic circulation with distance from left ventricle 35 mm Hg entering the capillaries 0 mm Hg entering the right atrium 3 Mean Arterial Pressure (MAP) MAP = DBP + (0.33 x [SBP - DBP]) 4 2  Mean Arterial Pressure (MAP) MAP = DBP + (0.33 x [SBP - DBP]) We spend more time in diastole. What is MAP if SBP is 120 and DBP is 80? 5 PRELOAD 6 3  With someone around you, discuss the factors influencing cardiac output I will ask you to share in 3 minutes 7 PRELOAD 8 4  SV and HR 9 Factors Affecting Stroke Volume (previous slide) Contractility: the forcefulness of contraction of the ventricle fibers, depends on the calcium kinetics and agents that increase or decrease the availability of calcium in sarcolemma Preload: the degree of stretch of the heart before contraction (Frank-Starling Law), preload is proportional to EDV (more blood, more stretch) Afterload: the pressure that must be overcome before a semilunar valve opens and blood can be sent to pulmonary and systemic circulation 10 5  Other Factors Influencing Blood Flow and Stroke Volume 11 Venous Return Volume of blood flowing back to the heart from the systemic veins depends on pressure difference from venules (16 mm Hg) to right atrium (0 mm Hg) Pressure difference between venous side to the right heart normally is enough to drive blood back to the right heart Two extra mechanisms: 1) muscle pump 2) respiratory pump 12 6  Muscle Pump Action: Helps driving the blood back to the RH through a milking action Example: end of a marathon Video 13 Respiratory Pump: During inhalation the diaphragm is pushed down and there is a pressure difference between the abdominal (high) to the thoracic cavity (low) This drives blood back to the RH 14 7  PRELOAD RESPIRATORY PUMP 15 Velocity of Blood Flow The velocity of blood flow is inversely related to the CSA of blood vessels Capillaries are the smallest blood vessels, but have the greatest total CSA 16 8 17 Some helpful tools from WP 18 9  See MAP Chart: Factors Influencing TPR 19 PRELOAD 20 10  Systemic Vascular Resistance (SVR) or Total Peripheral Resistance (TPR) Sum of all friction between blood and the walls of vessels Influenced by: 1) size of lumen (diameter, VC, VD) 2) blood viscosity 3) total blood vessel length 21 How does this change in the diameter of the lumen affect flow? R  1/d4 R = resistance d = diameter The smaller the diameter of the vessel, the greater resistance it offers to blood flow. 22 11  Vasoconstriction vs. Vasoconstriction vs Vasodilation Vasodilation BF  Blood Vessel  Diameter,  Resistance,  BF,  BP 23 Vasoconstriction vs. Vasoconstriction vs Vasodilation Vasodilation BF  Blood Vessel  Diameter,  Resistance,  BF,  BP 24 12  Discuss these with someone around you for 5 minutes 1) How would a decrease in muscle pump activity influence MAP? When would this happen? 2) How would an increase in blood volume influence MAP? How might this happen? 3) How would a decrease in hematocrit influence MAP? How would you decrease your hematocrit? 4) How would epinephrine influence MAP? Can you think of an example? 25 Questions? 26 13