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Cardiac Output (Factors that regulate Heart Rate (Nervous system (SNS:…
Cardiac Output
Factors that regulate Heart Rate
Nervous system
SNS: increases HR during stress/anxiety or exercise
Positive Chronotropic Factors: Increase heart rate; exercise, adrenalin, heat
PNS: dominates the stimulation of the heart, reduces rate of SA node thru vagus nerve signals
Negative Chronotropic Factors: Decrease heart rate; Cold, rest
Other factors that influence heart rate: Age, Gender, Exercise, and Body Temperature
Heart Rate: speed at which the heart beats
Stroke Volume
: The amount of blood pumped by the left ventricle of the heart in one contraction.
It Is determined by using the formula:
SV = EDV(End Diastolic volume) - ESV(End Systolic volume)
Factors that regulate stroke volume
Preload: Amount ventricles are stretched by contained blood
the higher the preload, the higher the stroke volume
Contractility: Cardiac cell contractile force
Factors that influence contractility
Positive inotropic agents: epinephrine, thyroxine, and glucagon
Negative inotropic agents: acidosis, rising extracellular K+ levels, and drugs called calcium blockers
Afterload: Back pressure exerted by blood in the large arteries leaving the heart
CO= SV x HR
CO = (EDV-ESV) x HR
Cardiac Output:The amount of blood pumped out by each ventricle in one minute