Physiology 3120 Lecture Notes - Stroke Volume, Afterload, Parasympathetic Nervous System

• School: Western University
• Department: Physiology
• Course: Physiology 3120
• Professor: Tom Stavraky

Document Summary

Mechanical performance of the heart: factors controlling cardiac output. Preload: amount of blood in ventricle before it contracts. Frank-starling curve: a (control, b (with sympathetic stimulation); at a given edv, stroke volume increases with, c (with parasympathetic stimulation); at a given edv, stroke volume decreases sympathetic stimulation with parasympathetic stimulation. The force against which the heart has to pump is the afterload; pressure in aorta is the afterload faced by the lv; pressure in pulmonary artery is the afterload faced by the rv. If the afterload becomes very high (as in severe hypertension), then the heart fails. Cardiac output = oxygen consumption/[ao2] [vo2] (rearranged formula) Inject known about of dye into right atrium/vena cava goes first to pulmonary circulation, then to systemic. Measure the concentration of dye in the blood. Cardiac output = amount of dye injected / (mean concentration in arteries * duration of first circulation) Stop dividing during early postnatal life; rather, grow by hypertrophy (cells get bigger)