NRSG 110 Cardiac.docx - Assessment of cardiovascular function \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 Endocardium inner layer

NRSG 110 Cardiac.docx - Assessment of cardiovascular...

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Assessment of cardiovascular function Endocardium : inner layer endothelial tissue that lines the inside of the heart and valves Myocardium: middle layer made up of muscle fibers and responsible for pumping action. Epicardium : outer layer and inner most layer of pericardium Pericardium : thin sac made up of two layers that covers the heart. In between the layers there is about 20mL of fluid that keeps the heart lubricated during systole Diastole : pressure during relaxation, all four chambers of the heart are filling and are at rest Systole : contraction of the atria and ventricles, this doesn’t happen at the same time, first the atria contract then the ventricles (lub-dub sound) Coronary arteries : right and left supply blood to the heart. When these arteries get clogged or the heart is not pumping sufficiently, it can lead to ischemia Cardiac conduction system : electrical activity of the heart Cardiac hemodynamics : the measurement of pressure inside each chamber of the heart Ventricular or atrial depolarization – contraction of the muscle (electrical activation of cell caused by influx of sodium into cell while potassium exits cell) Ventricular or atrial repolarization – muscle at rest (re-entry of potassium into cell while sodium exits) SA NODE: causes atriums to contract (atrial depolarization) Right atrium considered “pacemaker” 60-100 BPM SA node forms the P-wave – atrial contraction Cardiac Action Potential Phase 0 – sodium channels open; the inside of the cell becomes positive at 20-30 mV (BIG SPIKE) Phase 1 – sodium channels close, potassium channels open; potassium moves out of the cell causing light dip in action potential; inside of the cell now 0 mV Phase 2 (plateau phase) – slow calcium channels open; potassium moves out, calcium moves in; no change in mV; 0 mV Phase 3 – Fast potassium channels open allowing potassium to move out of the cell, results in a negative change in the cell (around -90 mV) Phase 4 – sodium and potassium pumps are activated; no major change of polarity in this phase
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Cardiac Output Stroke volume : amount of blood ejected with each heartbeat Preload : degree of stretch of cardiac muscle fibers at end of diastole Contractility : ability of cardiac muscle to shorten in response to electrical impulse After load : resistance to ejection of blood from ventricle Cardiac output : amount of blood pumped by ventricle in liters per minute Ejection fraction : percent of end diastolic volume ejected with each heart beat
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Which of the following is the normal pacemaker for the myocardium? A. Atrioventricular junction B. Bundle of His C. Purkinje fibers D. Sinoatrial node Which of the following best defines stroke volume? A. The amount of blood ejected with each heartbeat B. Amount of blood pumped by the ventricle in liters per minute C. Degree of stretch of the cardiac muscle fibers at the end of diastole D. Ability of the cardiac muscle to shorten in response to an electrical impulse Aging and the cardiovascular System Atherosclerosis -
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