test 5 - 1.Regulating Stroke Volume-CO is controlled by the...

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1.Regulating Stroke Volume -CO is controlled by the regulation of HR and SV. If CO is controlled then BP is controlled. a. Three Factors Determine Stroke Volume 1. Preload -determines the stretching of cardiac muscle which determines the volume of blood that is put into the heart (end of diastole) -the more the cardiac muscle is stretched out the more the heart will fill with blood and it will contract with more force -active = increased preload 2. Contractibility -the force of contraction that is generated -independent from stretching 3. Afterload -amount of arterial pressure that must be overcome to eject blood -afterload is considered to be constant and only a minor influence to afterload, unless there is stenosis of the pulmonary artery or aorta -contractibility and afterload are those factors that are most affected by pathologies -control of SV = control of CO = control of BP 2. Control of Stroke Volume -SV is controlled primarily by the ANS and an increase in preload -Normal SV results from normal EDV and normal contractibility a. Increased ANS -if autonomic stimulation increases then contractibility will increase and ESV will decrease. -this increases SV b. Increased Preload -if preload increases then EDV will increase -this increases SV c. Increased ANS and Increase Preload -an increase in both situations caused an increase in EDV, an increase in contractibility, and therefore an extreme increase in stroke volume 3. Control of CO -CO = SV x HR -CO = 5L -the CO of the left ventricle is pretty much equal to the CO of the right ventricle a. There are two ways that the heart stroke volume is controlled: 1. Intrinsic (aka Frank Starling Law of the Heart) -how the heart itself controls SV -done by increasing venous return, which then increases EDV, and therefore increases SV -the heart also increases preload, which means it incrases the amount of blood ejected and therefore increases SV
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i. Venous Return-when the veins are squeezed during contraction so that more blood is returned to the heart 2. Extrinsic -done by the ANS (sympathetic branch) -the SNS increases FOC for the heart -it also increases the release of Ca in skeletal muscle which increases cross bridge formation, and the contraction of veins and arteries in the skeletal muscle 4. Control of Heart Rate -one way to control blood pressure is to control cardiac output -SV tends to remain constant; therefore, CO is primarily regulated through altering HR -HR is regulated through the ANS Blood Vessels There are approximately 60,000 miles of vessels in the body. 1. Cardiovascular and the Lymphatic System -the lymphatic system receives fluid (plasma) from the arterial end of a capillary bed, filters, and then returns fluid back to the veins -lymph nodes filter the fluid before it is returned back to the veins. This is the way lymph nodes capture cancer cells. However, if these cancer cells get lose they can spread all over the body (by veins) 2. Histology of an Artery -an artery is any blood vessel that carries blood away from the heart (not
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This note was uploaded on 03/20/2008 for the course CBIO 2210 taught by Professor Wenzel during the Spring '07 term at UGA.

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test 5 - 1.Regulating Stroke Volume-CO is controlled by the...

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