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ENGL 1010 (7)
Chapter 18

Ch. 18 heart notes.doc

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ENGL 1010
Laura Sterrett

• Pulmonary circuit- blood vessels that carry blood to and from the lungs, serves gas exchange, short, low-pressure circulation • Systemic circuit- blood vessels that carry the functional blood supply to and from all body tissues, encounters about five times as much friction/resistance to blood glow as pulmonary circuit • Right heart- pulmonary circuit pump • Right atrium- oxygen-poor/carbon-dioxide rich blood entrance, pumps blood into right ventricle • Right ventricle- pumps oxygen-poor blood into lungs through pulmonary trunk, crescent shape • Lungs- place where blood unloads carbon dioxide and picks up oxygen • Pulmonary veins- carry newly oxygenated blood from lungs to left heart • Left heart- pulmonary circuit pump • Left atrium- oxygen-rich blood entrance from pulmonary trunk • Left ventricle- pumps blood from left atrium into aorta, walls are three times as thick as right ventricle, circular cavity • Aorta- pumps blood through arteries to the body tissues • Body tissues- place where gases and nutrients are exchanged across capillary walls • Superior and inferior venae cavae- pump oxygen-poor blood into right atrium • Cardiac output (CO)- amount of blood pumped out by each ventricle in 1 minute, produce of heart rate (HR) x stroke volume (SV) • Stroke volume- volume of blood pumped out by one ventricle with each beat, correlated with force of ventricular contraction • Average adult cardiac output is 5.25 L/min • Entire blood supply (about 5L) passes through each side of heart once per minute • Cardiac reserve- difference between resting and maximal CO • End diastolic volume (EDV)- amount of blood that collects in a ventricle during diastole, raises with how long ventricular diastole lasts and by venous pressure, normally about 120mL, affected by preload, affects SV intrinsically • End systolic volume (ESV)- volume of blood remaining in a ventricle after it has contracted, determined by arterial blood pressure (higher pressure=higher ESV) and the force of ventricular contraction, about 50mL, affected by afterload • SV = EDV – ESV • With each beat, each ventricle pumps out about 70mL of blood, about 60% capacity • SV is primarily affected by preload, contractility, and afterload • Frank-Starling law of the heart- critical factor controlling SV is preload • Preload- degree to which cardiac muscle cells are stretched just before they contract • Venous return- amount of blood returning to heart and distending its ventricles, stretches cardiac muscle • Increases of volume or speed of venous return like slow heart rate or exercise increase EDV and SV and contraction force • Contractility- extrinsic factor influencing SV, contractile strength achieved at a given muscle length, independent of muscle stretch and EDV, increase in contractility due to gr
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