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USC BISC 307L - Cardiovascular System 1
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Anatomy of Cardiovascular systemDon’t need to know a lot of anatomy 3 essential things you need to know (diagram on right)The only blood vessels across which exchange of material occurs are the capillariesTwo circulatory systems: pulmonary and systemicThe heart is two pumps in oneRight side pumps blood to lungs and left side pumps to bodyOutput of one is input of otherIn 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 state3. 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 capillariesWhy do we need two hearts?Fish only have one heart- won't ever amount to muchNext slidePressure, Flow, and ResistanceAdvantage of two heartsRelationship between pressure flow and resistanceWhat drives the flowFluids 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 pressureFlow rate (Q) is proportional to the pressure gradientPressure is pushing flow through a resistance and so the rate is inversely proportional to resistanceDeterminants of Vessel ResistanceWhat 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^4But in most conditions viscosity is the same so its pretty much constant so resistance is proportional to L/r^4The total length of the vessels in the systemic circulation are much longer that the pulmonary circulation and therefore the systemic network has higher resistanceThe resistance of tube 1 is much greater in the smaller radius tube than the larger radius tube (right figure)The flow rate is proportional to the pressure/resistance like ohms lawIf 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 PRESSURENot 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 aboutConclusionsVasoconstriction causes the radius to reduce and reduce flow rate—makes sense nowRegional differences in the state of vasoconstriction will redirect blood flow (vasodilate other areas)Mean Arterial Pressure (MAP)The left ventricle contractshigh pressureblood to aortastretches the arteriesThis stretching of the arteries is important because the arteries have to store some of this energyWhen ventricles are relaxed their pressure has to be zeroThis 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)Arteries are elastic- when heart relaxes, the arteries store some of that pressure (BP = 12080 not zero)What is the average pressure? Mean arterial pressureIt 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 flowWhen you take pulse, this is the stretching of the walls of the arteryFunctional Anatomy of the Heart-1Won't go over this but need to know the general idea- need to be able to draw the heartFunctional Anatomy of the Heart-2Functional Anatomy of the Heart -3Functional Anatomy of the Heart-4Cardiac Muscle cellsStriated- cells are a little shorter. Can be straight or branched, connect to each otherConnections have two functions1. Must be strong- heart contractions throughout whole organ2. Have to have a lot of gap junctions- the AP that triggers contraction must spread from cell to cellHighly invaginated with lots of desmosomes to transmit mechanical forceFunction of fibers is to contract and generated force (99%)1% of fibers lost the ability to contract and instead just generate and transmit action potentialAction 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+ channelsHave a lot more mitochondria than skeletal muscle because never rests and oxidativeBISC 307L 1st Edition Lecture 23 Current Lecture- Anatomy of Cardiovascular systemoo 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 capillarieso Two circulatory systems: pulmonary and systemico The heart is two pumps in one o Right side pumps blood to lungs and left side pumps to bodyo Output of one is input of othero 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 capillarieso Why do we need two hearts?  Fish only have one heart- won't ever amount to much Next slide- Pressure, Flow, and Resistanceo 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


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