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Lecture 5 – Regulation of Blood flow

Lecture 5 – Regulation of Blood flow -...

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Lecture 5 – Regulation of Blood flow Regulation of Blood Flow Overview o Cardiac output: one mode of blood flow focuses mainly on systemic circulatory system but applies to pulmonary circulation also is total blood flow to either the systemic or pulmonary circulatory systems o Organ blood flow is partially dependent on : cardiac output local (organ) events o regional blood flow within an organ/tissue Cardiac Output o directly influenced by : product of HR and stroke volume o Indirectly influenced by: autonomic nerves (specifically the sympathetic division ) what effect would stimulating sympathetic nerves have on blood flow? o blood flow is cardiac output, the sympathetic nerves augment HR, and nothing else here changes blood flow will increase if we stimulate the parasympathetic nerves, o vagus nerve of the parasympathetic nerve slows HR cardiac output and blood flow will decrease temperature increase in temperature will increase flow decrease in temperature will decrease flow filling pressure synonyms: preload, atrial pressure (of the right atrium) inotropic state has to do with the mechanical behavior of the myocardium how forceful and vigorous a contraction is the vigor of the contraction can also affect blood flow Filling Pressure o figure represents right atrial pressure (RAP, filling pressure), one indirect determinant of cardiac output o two functions of this graph: cardiac functions (cardiac output – blood flow) vascular functions (expressed as vascular function curves or Slide 1 Slide 2 the direct and some indirect determinants of cardiac output (total blood flow) Slide 3
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venous return) o both functions are circulatory functions o variable is filling pressure refers to the volume of blood in atrium during diastole when the atria contract, during atrial systole, the ventricles are relaxed, and the pressure inside atrial determines how much atrial blood get into ventricle o preload : influence of vol blood inside atrium on atrial myocytes (muscle cells that make up the wall of the atrium) the greater the vol of blood, the more the myocytes are stretched the greater the stretch during diastole, the greater the contraction during systoles (preload) – the volume of blood stretches during systole o on graph: at a right atrial pressure of 2 mmHg, --there is a single point of intersection of the 2 curves—cardiac output/venous return is 5 L/min o what will happen if we increase right atrial pressure (preload filling pressure) imagine, we double pressure from 2 mmHg 4 mmHg this would happen under controlled conditions in laboratory there are also diseases that increase right atrial pressure when we increase the right atrial pressure, 2 things happen: 1) cardiac output increases from 5L/min to 7.2-.3 L/min o increases bc increasing the stretch of right atrium will increase its force of contraction, which will fill left ventricle of blood and stretch
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