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Lecture 22

Cardiac Pumping

Cardiac Cycle Sequence of contraction and relaxation. 4 valves, 2 A-V,Aorti/Pulmonar, keep blood flow one way.
Diastole Relaxed heart, time for filling. End diastolic volume ~ 130 mL
Atrial Systole Contracts first completes filling of ventricles
Ventricular Systole Follows atrial contraction. Contraction spreads upward, pressure must be greater than aorta to open aortic valve.
Aortic Pressure Load left ventricle works against high BP puts greater load on heart.
Ejected Blood Volume ~70-90 mL of blood ejected per beat. ~ 65 mL of end diastolic volume. Lower HR means higher ejected volume.
Heart Rate Dependence The max heart rate is (220-age), rates above 180 dec. filling time. Must be motivated to exceed 180. This can dec. cardiac output. Potentially life threatening.
Arterial Pulse Arterial walls expand to hold blood. Rebounds during diastole - creates pulse. Little drop in BP throughout arteries.
Heart Sounds Closing of valves-turbulent blood flow creates sound. Low pressure AV (mitral and tricuspid) first, then high pressure aortic and pulmonary valves, diff. sound intensifies.
Murmurs non- laminar (non smooth)flow-sound when valves should be closed.
Valve Stenosis Stiff valve-small opening. Turbulent flow as blood squirts through.
Valve Insufficiency Valve leaves dont properly mesh. Children w/ improper valve closure, sometimes outgrow this murmur as growth alters valve alignment.
Cardiac Output Amount of blood pumped per min.
Stroke Volume x Heart Rate =CO ~ 7 oml @ 70 beats per min=~5L/min. Body has about 5 L of blood. Circulation time = 1 min.
Starling's Law Stroke volume control raises venous return stretches cardiac muscle rasies force raises CO. More actin myosin interaction, less thick z line contact less thin - thin overlap, more Ca2+ release. Stronger contraction, more SV, more CO
Neural Influences Both SV and HR changed
Parasympathetic Dominant at rest. Cut vagus nerve to heart, HR inc. from 70-100 immed. Exercise raises parasymp output lowers resting. HR: may go to 30-40.
Sympathetic Inc. Ca2+ channel opening. Faster depolarization causes inc. HR. More Ca2+ causes more force, causes inc. SV
Created by: danamarie9323