BIOM20002 Lecture Notes - Lecture 56: Hypovolemia, Peptic Ulcer, Hematemesis

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15 Sep 2018
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Pressure maintained by elasticity of aorta and valve which prevents backflow. Coronary blood flow depends on coronary perfusion pressure (cpp) Aortic pressure is essentially systemic bp ~ 120/70 (120mmhg during systole, 70 mmhg in diastole) Or coronary venous pressure whichever is higher. So lv coronary perfusion only occurs during diastole. Lv pressure lv 120/5 rv pressure 25/2 mmhg. Rv coronary perfusion occurs in diastole and systole. Tachycardia; short diastole and reduced perfusion time for myocardium. High end diastolic pressure: reduces coronary perfusion pressure. Low systemic vascular resistance (sepsis, aortic regurgitation) cause low aortic diastolic pressure --> low coronary diffusion pressure. Sympathetic innervation - catecholamines can shift the curve. Coordination of contraction: conducting system of heart responsible. Cell with fastest rate of autorhythmicity acts as the pace maker. Pacemaker: sa node ~70 bpm - altered by ans. Av node (50 bpm) slows conduction to ensure atria contract before ventricles. Purkinje fibers (25-40 bpm) enable ventricles to contract from apex to base.

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