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USC BISC 307L - Cardiovascular System 1
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BISC 307L 1st Edition Lecture 23 Current Lecture Anatomy of Cardiovascular system o o Don t need to know a lot of anatomy 3 essential things you need to know diagram on right o The only blood vessels across which exchange of material occurs are the capillaries o Two circulatory systems pulmonary and systemic o The heart is two pumps in one o Right side pumps blood to lungs and left side pumps to body o Output of one is input of other o In some cases capillaries don t lead into venules into veins 1 hypothalamic hypophyseal portal vein 2 Second example is the blood supply to the liver can receive blood through the hepatic portal vein capillaries drain into veins positions the liver to handle the flood of nutrients that come out of the intestine during the absorptive state 3 Third portal system has the structure of the portal system is in the kidney the glomeruler capillaries the venules do not go to a vein into the heart but rather into another set of capillaries o Why do we need two hearts Fish only have one heart won t ever amount to much Next slide Pressure Flow and Resistance o Advantage of two hearts Relationship between pressure flow and resistance What drives the flow Fluids flow down pressure gradients either liquids or gases so in order to get blood to circulate there must be pressure gradients hydraulic pressure mmHg High pressure low pressure Flow rate Q is proportional to the pressure gradient Pressure is pushing flow through a resistance and so the rate is inversely proportional to resistance Determinants of Vessel Resistance o o What determines blood vessel resistance For fluid flowing through a tube of uniform diameter through length L and radius r the resistance of this vessel 8L n viscosity pi r 4 which becomes Ln r 4 But in most conditions viscosity is the same so its pretty much constant so resistance is proportional to L r 4 The total length of the vessels in the systemic circulation are much longer that the pulmonary circulation and therefore the systemic network has higher resistance o The resistance of tube 1 is much greater in the smaller radius tube than the larger radius tube right figure o The flow rate is proportional to the pressure resistance like ohms law o If you change overall resistance of the system and the flow is the same you will change the pressure of the blood flow only happens when resistance change is widespread this will change BLOOD PRESSURE o Not all of the types of vessels are equally important in regulation of vasoconstriction and dilation the bigger vessels arteries are not capable of this vasoconstriction Veins are not very good either so it is the regulation of arteriolar vasoconstriction and dilation that we are talking about o Conclusions Vasoconstriction causes the radius to reduce and reduce flow rate makes sense now Regional differences in the state of vasoconstriction will redirect blood flow vasodilate other areas Mean Arterial Pressure MAP o o The left ventricle contracts high pressure blood to aorta stretches the arteries o This stretching of the arteries is important because the arteries have to store some of this energy o When ventricles are relaxed their pressure has to be zero o This means that the relaxation phase has to be longer than the contractile phase because it will take longer to fill the heart than it will to contract due to less pressure o Arteries are elastic when heart relaxes the arteries store some of that pressure BP 120 80 not zero o What is the average pressure Mean arterial pressure It is 93 not the average of 120 and 80 because it will be closer to diastolic pressure because there is more time taken to relax than contract Proportional to cardiac output L min times the peripheral resistance total resistance of all the vessels to blood flow o When you take pulse this is the stretching of the walls of the artery Functional Anatomy of the Heart 1 o o Won t go over this but need to know the general idea need to be able to draw the heart Functional Anatomy of the Heart 2 o o Functional Anatomy of the Heart 3 o o Functional Anatomy of the Heart 4 o Cardiac Muscle cells o o Striated cells are a little shorter Can be straight or branched connect to each other o Connections have two functions 1 Must be strong heart contractions throughout whole organ o o o o o o 2 Have to have a lot of gap junctions the AP that triggers contraction must spread from cell to cell Highly invaginated with lots of desmosomes to transmit mechanical force Function of fibers is to contract and generated force 99 1 of fibers lost the ability to contract and instead just generate and transmit action potential Action potential of the hear originates in the heart tissue MYOGENIC instead of neurogenic Less sarcoplasmic reticulum in cardiac muscle than skeletal muscle The Ca2 that triggers contraction only partly comes from the SR for cardiac muscle The rest comes through the plasma membrane through Ca2 channels Have a lot more mitochondria than skeletal muscle because never rests and oxidative


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