lecture06

lecture06 - Thursday, January 20, 2005 I. Structure II....

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Thursday, January 20, 2005 I. Structure II. Cardiac cycle (heartbeat) III. Cardiac output A. Amount B. Regulation C. Pumping efficiency D. Blood flow (Fig. 49.10) E. Control/regulation of blood flow/blood pressure (both local and systemic) 1. Background a. Pressure = P i. P 1 into vessel, P 2 exiting vessel b. Blood flow = (P 2 – P 1 ) / (resistance of vessel) = ΔP / R i. R is proportional to 1 / r 4 where r = effective radius of vessels 2. Local control of blood (Fig. 49.18) a. Autoregulation: each tissue regulates own blood flow i. Arterioles constrict/dilate ii. Pre-capillary sphincters on arterioles (smooth muscle cuffs) (A)Respond to local chemical environment (1) If O 2 low, CO 2 high smooth muscle relaxes more capillaries open increased local blood flow, increased O 2 delivery, CO 2 more effectively carried away 3. Regulation of blood pressure a. Short term regulation i. Stretch receptors (measure pressure) in artery walls leaving heart (A)Send signal to brain ii. Chemoreceptors (respond to O 2 levels) in artery walls leaving heart (A)Send signal to brain iii. Hormones (A)Vasopressin (B) Angiotensin b. Long term regulation
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lecture06 - Thursday, January 20, 2005 I. Structure II....

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