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9 Cards in this Set

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  • Back
Be able to discuss the equation CO = SV x HR
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
How is the Cardiac Rate regulated by the nervous system?
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
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
What 3 variables determine stroke volume?
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
How is stroke volume regulated?
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
What is the Frank-Starling Law of the heart?
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
How does venous return affect stroke volume?
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
What forces push the blood through the veins back to the heart?
Dependent on:
Blood volume and venous pressure
Vasoconstriction caused by Sympathetic
Skeletal muscle pumps
Pressure drop during inhalation
Be able to describe the fluid exchange between capillaries and tissues.
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