BCMB 230 1st Edition Lecture 16 Outline of Last Lecture I.Cardiovascular SystemII.BloodIII.HeartIV.ValvesV.PacemakersVI.Differences Between CellsOutline of Current Lecture I.Physics of Blood FlowII.Physics of the HeartIII.Control of Blood FlowCurrent LectureBlood FlowI. Physics of Blood Flow Laminar flow-normal condition of vessels; smooth surface, little turbulenceEquation: F=∆P/RFlow (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 wastePressure (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 butoxygen 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 pressureFlow 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 gradientR= 8Lɳ/πr4Since only looking at relationships, we can ignore constants 8 and πLength (L)-length of vesselViscosity (ɳ)-thickness of bloodRadius of Vessel (r)-responsible for regulation of flow and pressureLength 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 16Regulate viscosity so that it is constant.Regulate pressure and flow in circulatory system through regulating vessel diameter/radius.-vasoconstriction, vasodialationBlood volume has effect on pressure and flow.II. Physics of the HeartCO= SV x HRCardiac output (CO)-how much blood is moving out of the heartStroke volume (SV)-how much blood is moving with each heartbeat/contractionHeart 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 beatsSV= EDV – ESVEndsystolic (ESV)-volume of blood after contractionEnddiastolic (EDV)-volume of blood before contractionFactors 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 enddiastolicEndsystolic:- 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 calciumavailability; 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 proportionalThe 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 containerIII. Control of Blood FlowTwo 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 levelsMyogenic response-in smooth muscle; stretch influencing vessel diameter (dilation or