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A&PII Ch 22 Physiology of the Cardiovascular System.docx

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Health Science
HLSC 1201U
Elita P.

Ch 22Physiology of the Cardiovascular System - Hemodynamics – collection of mechanisms that influence the dynamic (active and changing) circulation of blood - Circulation control mechanisms must accomplish: maintenance of circulation, and varied circulation according to needs at that point in time ex. after digestion, you need large amount of blood to digest vs. exercise- blood flowing to limbs, circulating faster. - The heart as a pump: The heart muscle pumps the blood, needs to be organized by nerve cells - The SA node is the pace maker, specialized pace maker cells within have an intrinsic rythym Electrocardiogram (EKG)/Cardiac Cycle - 1. Relaxation. - 2. P wave = causes atrial walls to depolarize - 3. Contraction of the atria. - 4. QRS wave = atria repolarize (relax) and ventricular walls depolarize (contract) - 5. T wave = ventricular walls repolarize - 6. Once ventricles are completely repolarized, the voltage returns to the baseline - Contraction (systole) and relaxation (diastole) of both atria and both ventricles - Avg. time = 0.8 s - Step process: 1. Atrial systole (contraction of atria) > 2. Isovolumetric ventricular contraction > 3. Ejection (blood gushes out of heart) > 4. Isovolumetric ventricular contraction > 5. Passive ventricular filling - Isovolumetric pressure: Pressure in heart remains the same until pressure forces blood out (breaking point, high BP of 120, pressure of 121 and aortic valve opens, blood rushes out. - Atrial systole: P wave triggers atrial contraction, increased pressure pushes blood out of atria into relaxed ventricles via open AV valves - Isovolumetric ventricular contraction: R wave triggers ventricular contraction, AV valve closes (lub), SL valves stay closed - Ejection: SL valves open, blood enters arteries; rapid ejection  reduced ejection (T wave) - Isovolumentric ventricular relaxation: Onset of ventricular diastole, closure of the SL valves (dup), AV remain closed - Passive ventricular filling: Ongoing diastole, AV valves open; rapid filling  reduced filling (diastasis) - Blood flows because a pressure gradient exists; always flowing from areas of high pressure to areas of low pressu
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