PHIS 206 1st EditionLecture 13Outline of Last Lecture I. How The Blood Works―MechanicalII. How The Blood Works―Blood Flow III. External Factors that Modify Cardiac OutputIV. Electrical Properties of the Heart V. Conductive FibersOutline of Current Lecture I. Action PotentialsII. FluidsIII. AnatomyIV. CirculationV. Physical PropertiesCurrent LectureI. 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 outII. 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 moreThese 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 lessIII. 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 HgIV. 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 capillaries2.) 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 endo Fluids stay in ECF Thumb should blowo RELAX: pressure can only go to 40 mm Hg, thumb expands BUT connective tissue controls the situationV. 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”
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