Lecture 14 - CO, BP, VR Flashcards
cardiac output is equal to what
heart rate x stroke volume
cardiac index is equal to what
cardiac output / BSA
stroke volume is determined by
preload, contractility, afterload
what are the 4 determinants of cardiac output
- heart rate
- preload
- contractility
- afterload
describe preload
all factors contributing to passive ventricular wall stress or tension at the end of diastole
what is the most important factor in stretching cardiac muscle
venous return
what are the 3 outcomes of the frank-starling mechanism
- regulating moment to moment changes in SV
- responsible for balancing outputs of L and R ventricles
- prevents “back-up” of blood on one side of the heart
Venous return is equal to
the difference in mean systemic filling pressure and right atrial pressure
increased venous return will ____ ventricular filling and ____ stronger contractions
increase; increase
what 4 factors influence venous return
- blood volume
- venous compliance
- skeletal muscle pump
- respiratory pump
T/F: an increase in venous return will increase cardiac output
TRUE
what are 4 things used to estimate preload
- venous return
- hydration/dehydration
- pressure in atria/ventricle
- central venous pressure
what is compliance
relationship of V / P and the distensibility of ventricles
T/F: a compliant ventricle is stiff
FALSE - easily stretched
why would ventricles lose compliance
- ischemia
- age
- heart disease
- infiltrative disease
if a ventricle is ______ it will require higher pressure to fill
stiff or compliant
stiff
describe afterload
- tension generated in ventricular myocardium for ejection
- inversely proportional to stroke volume
how is the afterload estimated
- ventricular myocardial wall tension
- systemic vascular resistance
- diastolic BP
T/F: systolic arterial BP is a good index of afterload
FALSE
define contractility
the speed with which myocytes would contract if no load were placed on the heart
contractility will increase due to the increase in what
calcium
stroke volume and contractility are ____ related
directly; increase/decrease with each other
B1 adrenergic receptors
- binds epinephrine and norepinephrine
- increases intracellular calcium
decreased contractility is a mark of
cardiac disease (DCM, myocarditis)
contractility is estimated by
- LV ejection fraction
- LV change in diameter
T/F: heart rate and pulse rate are different
TRUE
T/F: acetylcholine causes a negative chronotropic effect
TRUE
pressure drop across the vascular bed is
the product of cardiac output and systemic vascular resistance
systolic BP
highest pressure during ventricular systole
diastolic BP
the lowest pressure during ventricular diastole
Mean arterial pressure
organ perfusion pressure; correlates with diastolic value
normal blood pressure in dogs
120/80 (90)
what must be the mean arterial pressure to maintain organ perfusion
60 mmHg
what are the determinants of blood pressure
- cardiac output
- peripheral vascular resistance
- blood volume
- blood viscosity
- elastic or arterial walls
how is BP directly measured
arterial catheter
how is BP indirectly measured
doppler flow
oscillometric BP
