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9 Cards in this Set
- Front
- Back
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Be able to discuss the equation CO = SV x HR
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Is volume of blood pumped/min by each ventricle
Stroke volume (SV) = blood pumped/beat by each ventricle Heart rate (HR) = the number of beats/minute CO = SV x HR Total blood volume is about 5.5L |
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How is the Cardiac Rate regulated by the nervous system?
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Without neuronal influences, SA node will drive heart at rate of its spontaneous activity
Normally Sympathetic and Parasympathetic activity influence HR (chronotropic effect) Autonomic innervation of SA node is main controller of HR Sympathetic and Parasympathetic nerve fibers modify rate of spontaneous depolarization |
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How is the Cardiac Rate regulated by pacemaker cells
by hormones? |
Norepinephrine and epinephrine stimulate opening of pacemaker HCN channels
This depolarizes SA node faster, increasing HR ACh promotes opening of K+ channels The resultant K+ outflow counters Na+ influx, slowing depolarization and decreasing HR |
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What 3 variables determine stroke volume?
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End diastolic volume (EDV) = volume of blood in ventricles at end of diastole
Total peripheral resistance (TPR) = resistance to blood flow in arteries Contractility = strength of ventricular contraction |
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How is stroke volume regulated?
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End Diastolic Volume is workload (preload) on heart prior to contraction
Stroke Volume is directly proportional to preload and contractility Strength of contraction varies directly with EDV Total peripheral resistance = afterload which impedes ejection from ventricle Ejection fraction is SV/ EDV Normally is 60%; useful clinical diagnostic tool |
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What is the Frank-Starling Law of the heart?
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States that strength of ventricular contraction varies directly with End Diastolic Volume
Is an intrinsic property of myocardium As End Diastolic Volume increases, myocardium is stretched more, causing greater contraction and Stroke Volume |
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How does venous return affect stroke volume?
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Is return of blood to heart via veins
Controls End Diastolic Volume and thus Stroke Volume and Cardiac Output Dependent on: Blood volume and venous pressure Vasoconstriction caused by Sympathetic Skeletal muscle pumps Pressure drop during inhalation |
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What forces push the blood through the veins back to the heart?
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Dependent on:
Blood volume and venous pressure Vasoconstriction caused by Sympathetic Skeletal muscle pumps Pressure drop during inhalation |
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Be able to describe the fluid exchange between capillaries and tissues.
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Distribution of ECF between blood and interstitial compartments is in state of dynamic equilibrium
Movement out of capillaries is driven by hydrostatic pressure exerted against capillary wall Promotes formation of tissue fluid |
