BCMB 230 1st Edition Lecture 16 Outline of Last Lecture I Cardiovascular System II Blood III Heart IV Valves V Pacemakers VI Differences Between Cells Outline of Current Lecture I Physics of Blood Flow II Physics of the Heart III Control of Blood Flow Current Lecture Blood Flow I Physics of Blood Flow Laminar flow normal condition of vessels smooth surface little turbulence Equation F P R Flow F how much blood we are moving with more flow the better ability to carry nutrients oxygen and waste material if flow is not adequate there is a buildup of waste Pressure P force exerted on capillary walls important in order to get material to move from capillaries out into tissues if pressure is not adequate it reduces flow so materials can be carried out to tissues but oxygen and nutrients are not delivered effectively if pressure is too high it can cause damage Resistance R opposition to flow if looking at just resistance doesn t matter if low or high does not have an intrinsic effect resistance is critical because it helps us control flow and pressure Flow and pressure are directly proportional to each other if resistance is constant Resistance and pressure are directly proportional to each other if flow is constant Resistance and Flow are inversely proportional to each other if pressure is constant These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute in arteries constant pressure is a good assumption in veins there is much lower pressure cannot assume constant P because of pressure gradient R 8L r4 Since only looking at relationships we can ignore constants 8 and Length L length of vessel Viscosity thickness of blood Radius of Vessel r responsible for regulation of flow and pressure Length and resistance are directly proportional to each other Viscosity and resistance are directly proportional to each other Vessel radius and resistance are inversely proportional to each other exponential relationship change resistance by 2 then vessel radius changes by 16 Regulate viscosity so that it is constant Regulate pressure and flow in circulatory system through regulating vessel diameter radius vasoconstriction vasodialation Blood volume has effect on pressure and flow II Physics of the Heart CO SV x HR Cardiac output CO how much blood is moving out of the heart Stroke volume SV how much blood is moving with each heartbeat contraction Heart rate HR how many beats we have per minute pacemakers set intrinsic rate of the heartbeat controls SA node sympathetic nervous system can increase heart rate epinephrine and norepinephrine another source for epinephrine and norepinephrine adrenal medulla endocrine system parasympathetic nervous system can decrease heart rate acetylcholine increase in heart rate increases cardiac output assume stroke volume stays constant decrease in heart rate decreases cardiac output assuming stroke volume staying constant is a good assumption unless there is a very high heart rate it is true most of the time if heart rate is too high cardiac output will actually decrease because the heart is beating too quickly to fully refill between beats SV EDV ESV Endsystolic ESV volume of blood after contraction Enddiastolic EDV volume of blood before contraction Factors that influence both influence in venus return influence how much flood is getting into the heart Enddiastolic blood volume venus vasoconstriction influenced by sympathetic nervous system skeletal muscle pump respiratory pump all of these are preload all of these are directly proportional to enddiastolic Endsystolic Starlings Law the relationship between cardiac muscle and stretch increasing contraction through increasing stretch inversely proportional contractility increasing contraction strength independent of stretch use sympathetic nervous system contractility cannot be reduced under normal levels increase in calcium availability inversely proportional afterload resistance in arteries that are coming out of the heart primarily in the pulmonary trunk going into lungs and aorta going into systemic system direcly proportional The more blood in the heart the harder it is going to contract the less blood that is going to be left inside Can use the term volume in two different ways volume of fluid or volume of container III Control of Blood Flow Two main control systems to help control blood flow active hyperemia and flow autoregulation active hyperemia increase in activity of muscle metabolic activity causes production of metabolites byproducts ex lactic acid ADP dec in oxygen dec in pH which can build up these cues cause dilation in artery which increases blood flow to organ vessels then use vasoconstriction back to original size flow autoregulation decrease pressure in organ could be due to dec in systemic pressure or clot leads to a decrease in flow normal activity causes metabolites to build up with a decrease in stretch in smooth muscle causes to contract decrease stretch causes dilation in organ restores blood flow to normal levels Myogenic response in smooth muscle stretch influencing vessel diameter dilation or constriction