CV A&P Flashcards
cardiac output
SV x HR = CO
–amount of blood that the heart pumps out of the left ventricle each minute
CO and HF
CO is diminished in HF because the left ventricle is weakened and cannot adequately pump blood out of the chamber
SV is the difference between…
volume of blood at the end of relaxation and residual volume of blood remaining in the ventricle after ejection
three major factors influencing SV
(1) preload
(2) afterload
(3) myocardial contractility
preload
stretch of cardiac muscle cells before contraction
afterload
resistance that must be overcome in order to eject blood from the chamber
contractility
contractile capabilities of the heart
relationship between preload and SV
lower preload = lower SV
Frank-Starling Law
an increase in resting muscle fiber length results in greater muscle tension
ex. the heart has the ability to change its force of contraction in response to changes in venous return
hydrostatic pressure
a force that attempts to push fluid out of the capillary pores and into the interstitial and intracellular spaces
ex. water pushing pressure
oncotic (osmotic) pressure
force that attempts to pull fluid from the interstitial and intracellular spaces into the capillary
ex. water pulling pressure
Starling’s Law of Capillary Forces
oncotic pressure forces and hydrostatic pressure forces oppose each other at every capillary membrane and attempt to balance each other out
left ventricular afterload
primarily determined by aortic blood pressure
afterload and SV
a decrease in afterload will lead to a decrease in SV unless the heart compensates
determination of contractility
primarily determined by the amount of free calcium within the myocardial cell
contractility and SV
increased contractility increases SV by causing a greater % of the volume to be ejected
heart blood flow
vena cavae/coronary sinus –> right atrium –> right ventricle –> pulmonary artery –> lungs –> pulmonary veins –> left atrium –> left ventricle –> aorta
backward effect of failing left ventricle
creates a buildup of hydrostatic pressure in the left atrium, pulmonary veins, and pulmonary capillaries
forward failure effects
cause decreased perfusion of the brain, kidneys, and other organs
example of backward effect in LVF
pulmonary edema
crackles with mild pulmonary edema
fine crackles
crackles with severe pulmonary edema
coarse, bubble-like
sputum with severe pulmonary edema
pink, frothy sputum
LVF backward effects
–dyspnea
–cough
–orthopnea
–paroxysmal nocturnal dyspnea
–crackles in lungs
forward effects in LVF definition
–cause inadequate ejection of blood into the aorta and diminished perfusion throughout whole arterial circulatory system
–decreased perfusion of vital tissues activates a neurohormonal response that includes stimulation of RAAS, ADH, and SNS
adrenergic stimulation of heart
increases HR
adrenergic stimulation of vasculature
vasoconstriction
diminished perfusion and posterior pituitary
releases ADH, which acts on the nephrons to increase water reabsorption into the bloodstream and, in turn, leads to increased BV
