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UNC-Chapel Hill BIOL 252 - Cardiovascular System Part 3

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BIOL 252 1st Edition Lecture 19 Outline of Last Lecture I. Poll EverywhereII. ECG/EKGIII. Principles of Pressure and FlowIV. Heart SoundsV. Phase of Cardiac CycleVI. How much blood does the heart pumpOutline of Current LectureI. Changing Heart RateII. Changing Stroke VolumeIII. Cardiovascular SystemIV. Circulatory RoutesV. HemodynamicsVI. Blood PressureVII. What variables affect blood pressure?Current LectureI. Changing Heart Ratea. When blood chemistry changes, chemoreceptors provide info on pH and CO2i. High levels of blood CO2 = hypercapnia ii. Acidosis – pH is lower than normal (more acidic)iii. Accelerate heart rate – cardioacceleration eliminates CO2 and H+1. How? 2. Can get more blood to lungs quickly b. Baroreceptors provide info on blood pressurei. Hypertension: high blood pressure1. Cardioinhibition ii. Hypotension: low blood pressure1. Cardioacceleration – push more blood into arteries so pressure will rise iii. Think of arteries as elastic as opposed to pipes II. Changing Stroke Volumea. Inotropic agents affects on contractilityb. NE increases stroke volume 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.i. Ejection fraction= stroke volume / end diastolic volume ii. With more NE, increase ejection fraction iii. NE from adrenal medulla and/or sympathetic nerves (neuron releases it at a synapse or adrenal medulla releases into blood)c. ACh small effect on atriai. Decreases stroke volumed. Preloadi. Pressure of blood coming into ventricles that stretches myocardium ii. How do you have an elevated pressure/high preload?1. How do the veins move blood? Skeletal muscle pumpa. Activity of our muscles pushes blood in our veinsb. If exercising, elevates venous blood pressurec. Pushing blood into heart at greater rate than at restd. Ventricles stretch to accommodate more blood, and walls stretch = preload e. Heart contracts more strongly when stretchedf. Increases stroke volume so cardiac output increases iii. Frank-Starling Law: the greater the EDV, the greater the SV1. Greater the input, greater the output iv. Afterload: blood pressure in aorta and pulmonary trunk that resists ejection of ventricles 1. Hypertension increases afterload, reduces stroke volume2. Opposes the blood pressure generated in ventricle3. If high afterload, stroke volume decreases e. Immediate Effects of Exercisei. Proprioceptors can elevate heart rate without waiting for CO2 buildup1. Increase heart rate and stroke volume ii. Increase in venous return & preload => increase stroke volumeiii. Benefits1. Ventricular hypertrophya. Bigger cells = stronger heart => stronger contraction2. Increases resting stroke volume3. But cardiac output / needs are the same4. Decreases resting heart rate5. Increases cardiac reserve a. Different between maximum cardiac output and cardiac output at restIII. Cardiovascular Systema. Arteries: carry blood away from heart; high pressurei. More elasticii. Serve as sensory organs1. Carotid sinuses – baroreceptors respond to changes in blood pressurea. High blood pressure causes decrease in HR and vasodilation2. Carotid and aortic bodiesa. Chemoreceptors respond to change in blood chemistryb. Increased CO2 and low pH => increased HRiii. Systemic circuit: red arteriesiv. Pulmonary circuit: blue arteries b. Capillaries: connect arteries to veins; moderate pressurei. Capillary bedsii. Channel runs through centeriii. Why not perfuse all capillary beds?1. Not enough blood to do it 2. Its more efficient to build up concentration gradients of CO2 and O2c. Veins: carry blood towards heart; low pressurei. Where most blood residesii. Less elastic than arteriesiii. Thinner walls, less muscular iv. Low blood pressurev. How do we move low-pressure venous blood to heart?1. Muscular pumpa. One-way valves help to move blood toward heartb. Valve prevent it from going away from heartc. Contracted skeletal muscles push blood to open valve and move toward heart d.2. Respiratory pumpa. Helps to move blood toward heart during inspirationb. When you breathe in, thoracic cavity gets larger c. Adds pressure below, lowers pressure belowd. Blood moves from high pressure to low pressurei. From abdomen upward (where there is less pressure)3. Vasomotiona. If hypovolemic (low blood volume => low blood pressure), smooth muscle contracts to elevate venous pressureb. Constriction of blood vessels that helps to move blood4. Gravitya. For veins above heart, gravity assists in venous returnIV. Circulatory Routesa. Venous and arterial anastomoses b. Arteriovenous anastomosis (shunt)c. Portal systemd. Typical V. Hemodynamicsa. Principles of blood flow (mL/min)b. Blood flow is proportional to difference in pressurei. F is proportional to change in Pc. Consider resistancei. Opposes blood flowii. High resistance leads to less flowiii. Blood flow is inversely proportional to resistanceVI. Blood Pressurea. Because of pressure differences, blood flows away from aortab. Two pressures you can monitori. Systolic pressure (contraction) / diastolic pressure (relaxation)ii. 120/80 is considered normaliii. Systolic and diastolic pressure are different depending where it is taken c. More blood in capillaries than in aorta VII. What variables affect blood pressure?a. Cardiac outputi. HR X SVii. Greater cardiac output = greater BPb. Blood volumei. Water in – water outii. How do you get water in? Drinkingiii. How do you get water out? Urinate, respire, bleed, perspirationc. Peripheral resistancei. Sources of resistance1. Friction – movement of blood against vessel wall a. Vessel lengthi. Greater length = more friction b. Vessel diameter i. Large diameter = larger surfaceii. More fluid in middle flowing freelyiii. More interaction w/ smaller diameter = more friction iv. Dilate blood vessel diameter = increase resistance2. Viscositya. Determined by hydration, RBC count, albumen concentrationb. More viscosity = more resistance 3. Which one do we change? Vessel diameter d. How do we regulate blood pressure and flow?i. Autoregulation (local control)1. Metabolic byproducts stimulate vasodilation2. Local vasoactive chemicals control response to injury/infection3. Angiogenesis: growth of new vessels to meet oxygen demands of tissueii. Neural control1. Sympathetic NS controls vasomotion in response to pressure, or chemical changes a. Chemoreceptors stimulate vasoconstriction except in lungsb. Baroreceptors provide info


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UNC-Chapel Hill BIOL 252 - Cardiovascular System Part 3

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