Lecture 6 - 1 January 24, 2010 NPB113 Contractile...

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Unformatted text preview: 1 January 24, 2010 NPB113 Contractile Properties of the Heart 6-1 Outline Definition of Terms Intrinsic contractile properties of the heart Heterometric autoregulation (Frank- Starling) affect of changes in preload muscle fiber length Homeometric autoregulation affect of changes in afterload, aortic diastolic pressure, on contractile properties of the heart. Extrinsic Influences on the contractile properties of the heart Details of Heterometric Autoregulation using the Cardiac Cycle Homeometric Autoregulation using the Cardiac Cycle Assessing affects of intrinsic and extrinsic affects on the contractile properties of the heart using Cardiac Function Curves Effect of change in muscle fiber length & Contractility. Pressure Volume Loops Effect of changes in Muscle Fiber Length & Contractility 2 January 24, 2010 NPB113 Contractile Properties of the Heart 6-2 Definition of Terms Translation of Terms from Cardiac Muscle to the Contraction of the Whole Heart Muscle fiber length = End Diastolic Volume (EDV) Preload = End Diastolic Pressure (EDP) = End Diastolic Volume . EDV = End Systolic Volume + Venous Return . Afterload = Aortic or Arterial Diastolic Blood Pressure (ADP) Total Load = Preload + Afterload = EDP (or EDV) + ADP . External Shortening = Stroke Volume (SV) Auxotonic Contraction External shortening (ejection of the SV) with continued increase in tension or pressure. Therefore, contraction of the heart is not isometric nor is its isotonic during the ejection of the SV. For the heart, isovolumetric contraction has some characteristics of the isometric phase of an isotonic contraction because there is an increase in pressure but no change in volume (there is a change in heart 2 January 24, 2010 NPB113 Contractile Properties of the Heart 6-2 Definition of Terms Translation of Terms from Cardiac Muscle to the Contraction of the Whole Heart Muscle fiber length = End Diastolic Volume (EDV) Preload = End Diastolic Pressure (EDP) = End Diastolic Volume . EDV = End Systolic Volume + Venous Return . Afterload = Aortic or Arterial Diastolic Blood Pressure (ADP) Total Load = Preload + Afterload = EDP (or EDV) + ADP . External Shortening = Stroke Volume (SV) Auxotonic Contraction External shortening (ejection of the SV) with continued increase in tension or pressure. Therefore, contraction of the heart is not isometric nor is its isotonic during the ejection of the SV....
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Lecture 6 - 1 January 24, 2010 NPB113 Contractile...

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