BIOM20002 Lecture Notes - Lecture 56: Hypovolemia, Peptic Ulcer, Hematemesis
Document Summary
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.
