Physiology Exam 10 Study Guide Heart Contraction Pattern Continued Purkinje fibers PF depolarize ventricle s cells Work from bottom to top squeeze from bottom up b c outlets are up LV to aorta RV to pulmonary artery needed to get proper blood flow External measure Electrocardiogram EKG pattern of electrical activity being registered Y axis overall electrical charge NOT Vm of a single cell like in APs X axis time Electrical Activity 1 P wave when first contraction is occurring atrial depolarization Top down pushing blood into ventricle Delay due to hiding in bundles of His 2 QRS complex Ventricular depolarization Ventricles contracting from bottom up also obscures atrial repolarization 3 T wave Ventricular repolarization ends contraction in ventricles What about atrial relaxation Very small times out in QRS system it obscures atrial repolarization also occurring during this time Must finish one cycle before next one can start Sounds Lub Dub Lub post QRS ventricle squeezes blood up closes cuspid valves to prevent backflow Sounds are the valves closing can only go up through semilunar valves and not back into atria Bicuspid valve in LV tricuspid valve in RV Dub post T blood going out aorta pulmonary artery relaxing ventricles Close semilunar valves to maintain 1 way flow prevent backflow into ventricles Heart murmur doors not closing all the way blood flows in wrong direction backflow Fail to completely close the valve Lub sh dub Lub dub sh backflow Based on pattern we know if it is semilunar or cuspid but not which side Cardiologists listen to different parts of heart to find specific problematic valve Cardiac Cycle Heart creates BP the force getting blood moving to create convection needed to create distance movement that diffusion can t do on its own Blood Pressure contraction of space in the heart PV nRT Inverse relationship of P and V nRT are all constants in heart 2 phases fill then empty 1 cycle Systole 1 3 of time squeezing contracting for ejecting blood Diastole 2 3 of time relax for filing Takes longer to relax fill heart than contract Stroke Volume EDV ESV amount of blood ejected in 1 cycle EDV end diastolic volume pre contract volume When heart most opened filled with blood average 135 mL ESV end systolic volume post contract volume Can t empty all blood best squeeze leaves average of 65 mL Heart rate HR cycles min Cardiac Output CO SV x HR what heart is doing overtime 1 min Typical 70 mL beat x 70 bpm 4 9 L min Regulating of CO Changes possible HR or SV relatively independent Biggest change should change both Regulation of HR Autonomic Sympathetic fight or flight Increases HR 1 Input to SA node increased more APs Must tell heart to contract be ready to do so complete previous cycle 2 Increases conduction velocity ready for next cycle faster more cycles Parasympathetic exact opposite Decreases HR Decrease input to SA node decreases conduction velocity Others indirectly through autonomic system Epinephrine try to increase heart activity See in hospital shows after crash Body temperature changes rate of flow Cold keeps blood flow in core warm flow to surface to dissipate as heat Only in extreme conditions does heart must work harder Heart doesn t play a big role in normal temperatures Electrolytes affecting Vm calcium sodium potassium affect electrical activity Off balance of any ions are the heart can have impacts Endocrines Sex hormones when in love Estrogen testosterone gets heart doing more Sexual elders usually don t have high levels heart problems Regulation of SV 1 Increase EDV fill up heart more Increase contract force ejects more blood bigger SV when stretched a little Ex Stretching before game myosin pulling against actin string out to get most connections possible increase potential for cross bridge cycling Only a little stretching too much or will eliminate cross bridge from occurring by eliminating overlap like water balloon no contraction Too big of stretch Decrease force myosin can t grab actin no contraction Congestive heart failure heart overfilled stretched too far need to relax 2 Change in arterial pressure where blood is sent to Ventricle ejects to aorta on left side artery Pumping against pressure gradient out in system resistance Daughter pushing chair can t when Dr B is in it 3 Sympathetic Nervous System affects both SV and HR Epi Norepi will increase ability to heart to squeeze regardless of volumes Better squeeze Decrease ESV Increased SV SNS input increases strength of ventricular contraction regardless of EDV Blood Vessels All types are lined with endothelium plasma always inside tubes Tight junctions between them to protect blood act as barrier between blood and IF Arteries away from the heart defined based on direction Carry oxygenated blood usually except for pulmonary artery Flexible highly elastic decreases variation Yes no process either pumps or doesn t blood goes out or it doesn t Want continuous flow of blood to keep cells aerobic elasticity makes it possible by pushing on sides rebound occurs in diastolic resting Allows less variation keep continuous flow going Hardening in artery increased variation issues with cells sometimes force cells to be anaerobic Smooth muscle surrounds arteries can change the size of vessels changes BP hydrostatic pressure BP the starting factor Fluid pushes on walls to make vessel circular Ex Like a fire hose flat when no water swell when filled with water 2 components BP horizontal pressure Hydrostatic pressure perpendicular pressure More surface area less hydrostatic pressure like snowshoes Hydrostatic pressure very high b c very small wall low SA and high BP Aneurysm blood flows out of wall due to build up of pressure Arterioles smaller but more Less elastic Smooth muscle hydrostatic pressure much lower than arteries further from the heart more SA Capillaries smallest allow only 1 RBC to go through at a time not compressible cells Very thin walls 1 endothelial cell thick Allows diffusion to occur Site exchange distance critical of oxygen CO2 glucose Increased surface area low hydrostatic pressure necessary b c walls so thin Decrease flow rate to do necessary exchange slowest movement Like food traveling on a conveyer belt need time to get food hydrostatic pressure b c high SA in combination with low BP Venules Returning blood lower oxygen Thin walled Low hydrostatic pressure SA still relatively high far from heart Don t need walls to be that strong Buildings in cbus not built as strong as in Chicago LA
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