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Lecture 1.docx

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University of Otago
Regis Lamberts

Objectives:  Why a CVS?  Structure of the heart  The primary importance of this design of the CVS for maintaining blood flow and blood pressure  Physiological and physical factors of CVS and the equations relating to these variables  Typical values for pressure, flow and resistance, and their units  The importance of these relationships in the design and control of the CVS Heart: a pump which creates cardiac output Vessels: allow tissue perfusion Why do we have a cardiovascular system?  Supply tissue with adequate oxygen and nutrients  Removal of unwanted metabolic by-products such as CO2 and H+  Transport of substances and heat- often diffusion is not enough to get adequate nutrients etc. where it is needed.  In the Lungs and Tissues: diffusion is adequate as there are only short distances due to small vessels  Around the body bulk flow is created by the output of the heart, acts more rapidly over long distances:  Quick delivery to capillaries  Optimal exchange rate  Quick return to lungs Heart  arteries  arterioles  capillaries  venules  veins  heart 4-6 L blood, dependent upon body size Heart = pump  Muscular organ, sitting inside the pericardium  Cardiac muscle cells make up the myocardium  Right and left atria and ventricles  Ventricles have thicker walls because of higher pressure needing to be generated- and left thicker than right because systemic pressure > pulmonary pressure  Fibrocartilaginous ring contains valves. Valves:  Atrio-ventricular Valves:  Between atria and ventricles  Tricuspid: right  Bicuspid/ mitral valve: left  Ensure unidirectional blood flow  Opening and closing are passive, pressure dependent events  Semilunar Valves:  Aortic valve: between the left ventricle and the aorta  Pulmonary valve: between the right ventricle and the pulmonary artery  Both allow blood flow into the arteries during systole, while preventing back-flow of blood into ventricles during diastole  Opening and closing of these valves are also passive, pressure- dependent processes. Cardiac Muscle Cell:  Striated, multinucleate, branched contractile elements  Cell membrane; network of T tubuli through the sarcoplasmic reticulum for cell signalling  Many mitochondria which provide for the inexhaustible properties of the heart; continually beating uses up a lot of energy  Intercalated disc: gap junctions so that cardiomyocytes can communicate s
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