Physiologic Heart Function Flashcards
Cardiac index
the hemodynamic measurement equivalent of cardiac output
What does cardiac output vary by
body size
Why is cardiac output diminished in heart failure
the left ventricle is weakened and cannot properly pump
What is the key concept of heart failure
the stroke volume is compromised, perfusion is reduced, CO decreased
Preload
the volume of blood still in the heart at the end of diastole
End diastolic volume
blood empties into the right ventricle
Afterload
the amount of resistance the ventricle must overcome in order to pump blood out of the heart
When is there greater pulmonary resistance
greater afterload against the right ventricle
When is there greater systemic arterial vascular resistance
greater afterload against the left ventricle
Cardiac contractility
the myocardium’s ability to stretch and contract in response to filling the heart with blood
What do actin and myosin action create
force of contraction
What can afterload do to contractility
negatively affect contractility by increasing the heart’s workload
What is cardiac contractility influenced by
ANS, acid-base balance, elctrolytes
Inotropic function
the force of contraction of cardiac muscle
What is inotropic function influenced by
the amount of calcium available for activation of cardiac muscle filaments
Positive inotropic effect
sympathetic stimulation can increase force
Chronotropic function
the heart rate
Epinephrine inotropic and chronotropic effects
positive for both, makes the heart beat faster and stronger (sympathetic stimulation)
Frank-starling law
explains the relationship between cardiac contractility, preload, afterload, SV, and CO
Why do the ventricles adjust pumping force
to accommodate changing levels of preload and afterload
Starling’s capillary forces
2 opposing forces present at every capillary bed (hydrostatic and oncotic/osmotic)
Hydrostatic pressure
fluid in the blood attempting to force fluid out, into the intracellular/interstitial spaces
Oncotic pressure
pull fluid from intracellular/interstitial spaces back into the vessel
What is edema caused by
increased hydrostatic pressure in capillary causing imbalance and fluid leaks
