Cardio Study Guide - Cardiovascular physiology Review...

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Cardiovascular physiology Review Questions 1. Describe the different cell types that are found in the heart and detail the characteristic and action of each cell type. Smooth muscle cells and endothelial cells- line the arteries and veins Epicardium cells Fibroblasts- myocardium- collagen synthesis (key structural protein within the extracellular matrix), able to divide and proliferate P (pacemaker cells)- electrical impulse conduction, purkinje cells are large which allow rapid propagation of AP down His purkinje system Cardiomyocyte (contractile cell)- force producing cell- cross bridge cycling Represent 30% of total cell population, but because of weight the myocyte occupies about 75% of structural space Unable to proliferate 2. Which factors are associated with a shift or change of the myocardium with the chest cavity? Normal- age, weight, pregnancy, body shape, or shape of thorax Pathological- left ventricular hypertrophy, cardiomegaly, enlarged abdominal organs, pulmonary conditions (pneumothorax) 3. Coronary blood flow is influenced by numerous factors, however in general these factors can be classified into categories. Discuss these categories. Coronary blood flow is precisely matched to the oxygen and metabolic demands of the myocardium, the myocardium extracts all the oxygen that is delivered to it and therefore the major mechanism by which the myocardium increases oxygen delivery is to increase CBF , local metabolic control is the most important mechanism that serves to increase CBF. Physical factors Extravascular compression- “squeezing effect”-markedly reduces coronary blood flow especially during systole- outset of systole results in a reversal or profound decrease in blood flow to coronaries (60 ml/min to 0) but then reversed due to accumulation of metabolic by products in interstitial fluid compartment happens because of temporary “ischemia” that occurs during systole attempts to return to normal and then onset of diastole causes large increase in blood flow. Diastole is longer than systole which allows for significant amount of perfusion to myocardium. Order of events: contraction of LV increased pressure in LV with extravascular compression of LCA decrease LCA flow increase metabolic byproducts as a result of brief tissue ischemia vasodilation small increase in LCA blood flow secondary to vasodilation end of systole very large increase of LCA blood flow at onset of diastole Tachycardia- shortens diastole, less time for maximal coronary artery flow but local accumulation of metabolites vasodilates to compensate. Tachycardia in normal healthy heart can usually be maintained for a few days
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Neonates are more dependent on heart rate (120-140) because hearts are more stiff so rely on tachycardia to maintain cardiac output Intraventricular pressure - Increased intraventricular pressure decreases perfusion pressure (especially in presence of atherosclerosis), therefore the endocardium is the most
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