PHIS 206 1st Edition Lecture 13 Outline of Last Lecture I How The Blood Works Mechanical II How The Blood Works Blood Flow III External Factors that Modify Cardiac Output IV Electrical Properties of the Heart V Conductive Fibers Outline of Current Lecture I Action Potentials II Fluids III Anatomy IV Circulation V Physical Properties Current Lecture I Action Potentials Reach from S A node to every part of the heart before firing Cells do not get to spontaneously depolarize S A Node pacemaker when turned off rendered excitability decrease from 40 to 15 to etc Venus Return and Sympathetic Stimulation can increase cardiac output 5L If atria was not functioning 70 L would still be put out II Fluids Fluids gasses liquids Blood vessels pipes Ohm s Law relationship b w current voltage and resistance Current Voltage Resistance Flow is completely analogous to Ohm s Law Flow Pressure Resistance F 5L min P 100 mmHg in arteries total pressure so R 1 peripheral unit Poiseuille s Law Resistance Length Diameter 4 K If length is longer then resistance is more 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 If diameter is longer then resistance is less III Anatomy Arteries 100 mm Hg Arterioles Resistance vessels small opening smooth muscle that can constrict 40 mm Hg MOST RESISTANCE Capillaries small so many capillaries so not as much resistance 15 mm Hg Venules Veins 10 mm Hg Heart 0 mm Hg IV Circulation capillaries deliver nutrients to cells and remove waste products carbon dioxide ONLY place to get in out of circulation CAPILLARIES capillaries are extremely permeable everything except cells and proteins diffuse depends on plasma intracellular and other cells extracellular In the capillary conc of oxygen etc is high so the cell using the nutrients will obtain the capillaries nutrients when the nutrients diffuse out 1 Fluid volume reduces so pressure reduces in capillaries 2 Increase in osmotic pressure in capillaries as protein increases hydrostatic pressure decreases RESULT Forces on the beginning and end of the capillary EQUAL each other During passage through fluid nutrients and waste products do their job of diffusion Situation HAMMER HITS THUMB capillaries are damaged red cells proteins etc can diffuse out b c small openings become larger fluids are released and you don t reabsorb the fluid at the distilling end o Fluids stay in ECF Thumb should blow o RELAX pressure can only go to 40 mm Hg thumb expands BUT connective tissue controls the situation V Physical Properties Vessels can stretch under pressure Distensibility CHANGE IN VOLUME CHANGE IN PRESSURE Veins are the most distensible 5 times the arteries Compliance TOTAL CHANGE IN VOLUME CHANGE IN PRESSURE Volume on Venus Side 5 times the volume of arterial cell Plasma volume increases by 250 mm Hg 25 times as much will end up in veins 240 mm Hg and in arteries 10 mm Hg SUMMARY veins are compliance cells and storage vessels
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