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Lecture 22
Cardiac Pumping
| Term | Definition |
|---|---|
| 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 |
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