BIOL 252 1st Edition Lecture 19 Outline of Last Lecture I Poll Everywhere II ECG EKG III Principles of Pressure and Flow IV Heart Sounds V Phase of Cardiac Cycle VI How much blood does the heart pump Outline of Current Lecture I Changing Heart Rate II Changing Stroke Volume III Cardiovascular System IV Circulatory Routes V Hemodynamics VI Blood Pressure VII What variables affect blood pressure Current Lecture I II Changing Heart Rate a When blood chemistry changes chemoreceptors provide info on pH and CO2 i 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 pressure i Hypertension high blood pressure 1 Cardioinhibition ii Hypotension low blood pressure 1 Cardioacceleration push more blood into arteries so pressure will rise iii Think of arteries as elastic as opposed to pipes Changing Stroke Volume a Inotropic agents affects on contractility b 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 III 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 atria i Decreases stroke volume d Preload i 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 pump a Activity of our muscles pushes blood in our veins b If exercising elevates venous blood pressure c Pushing blood into heart at greater rate than at rest d Ventricles stretch to accommodate more blood and walls stretch preload e Heart contracts more strongly when stretched f Increases stroke volume so cardiac output increases iii Frank Starling Law the greater the EDV the greater the SV 1 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 volume 2 Opposes the blood pressure generated in ventricle 3 If high afterload stroke volume decreases e Immediate Effects of Exercise i Proprioceptors can elevate heart rate without waiting for CO2 buildup 1 Increase heart rate and stroke volume ii Increase in venous return preload increase stroke volume iii Benefits 1 Ventricular hypertrophy a Bigger cells stronger heart stronger contraction 2 Increases resting stroke volume 3 But cardiac output needs are the same 4 Decreases resting heart rate 5 Increases cardiac reserve a Different between maximum cardiac output and cardiac output at rest Cardiovascular System a Arteries carry blood away from heart high pressure i More elastic ii Serve as sensory organs 1 Carotid sinuses baroreceptors respond to changes in blood pressure a High blood pressure causes decrease in HR and vasodilation 2 Carotid and aortic bodies a Chemoreceptors respond to change in blood chemistry b Increased CO2 and low pH increased HR iii Systemic circuit red arteries iv Pulmonary circuit blue arteries b Capillaries connect arteries to veins moderate pressure i Capillary beds ii Channel runs through center iii 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 O2 c Veins carry blood towards heart low pressure i Where most blood resides ii Less elastic than arteries iii Thinner walls less muscular iv Low blood pressure v How do we move low pressure venous blood to heart 1 Muscular pump a One way valves help to move blood toward heart b Valve prevent it from going away from heart c Contracted skeletal muscles push blood to open valve and move toward heart d 2 Respiratory pump a Helps to move blood toward heart during inspiration b When you breathe in thoracic cavity gets larger c Adds pressure below lowers pressure below d Blood moves from high pressure to low pressure i From abdomen upward where there is less pressure 3 Vasomotion a If hypovolemic low blood volume low blood pressure smooth muscle contracts to elevate venous pressure b Constriction of blood vessels that helps to move blood 4 Gravity a For veins above heart gravity assists in venous return IV V VI VII Circulatory Routes a Venous and arterial anastomoses b Arteriovenous anastomosis shunt c Portal system d Typical Hemodynamics a Principles of blood flow mL min b Blood flow is proportional to difference in pressure i F is proportional to change in P c Consider resistance i Opposes blood flow ii High resistance leads to less flow iii Blood flow is inversely proportional to resistance Blood Pressure a Because of pressure differences blood flows away from aorta b Two pressures you can monitor i Systolic pressure contraction diastolic pressure relaxation ii 120 80 is considered normal iii Systolic and diastolic pressure are different depending where it is taken c More blood in capillaries than in aorta What variables affect blood pressure a Cardiac output i HR X SV ii Greater cardiac output greater BP b Blood volume i Water in water out ii How do you get water in Drinking iii How do you get water out Urinate respire bleed perspiration c Peripheral resistance i Sources of resistance 1 Friction movement of blood against vessel wall a Vessel length i Greater length more friction b Vessel diameter i Large diameter larger surface ii More fluid in middle flowing freely iii More interaction w smaller diameter more friction iv Dilate blood vessel diameter increase resistance 2 Viscosity a Determined by hydration RBC count albumen concentration b 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 vasodilation 2 Local vasoactive chemicals control response to injury infection 3 Angiogenesis growth of new vessels to meet oxygen demands of tissue ii Neural control 1 Sympathetic NS controls vasomotion in response to pressure or chemical changes a Chemoreceptors stimulate vasoconstriction except in lungs b Baroreceptors provide info on BP decrease BP vasoconstriction c Medullary ischemic reflex medulla monitors its own O2 levels decrease O2 stimulates increase HR and vasoconstriction iii Hormonal
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