Fewell - Coronary Blood Flow Flashcards
Hg is _ times as dense as H2O
13.6 times
1 cmH20 = _ mmHg
0.73
stroke volume
the amount of blood pumped by the ventricle duing one cardiac cycle
both right and left heart eject ___
eject the same amount of blood
calculating stroke volume
SV = End-diastolic volume - end-systolic volume
ex: 70mL = 120mL - 50mL
what is normal stroke volume
70mL
normal end-diastolic volule
120mL
normal end-systolic volume
50mL
Ejection Fraction formula
stroke volume/end-diastolic volume
ejection fraction ideal value
over 55% for healthy
>below and you may tire more easily during activity or if very low at rest
ejection fraction definition
compares the amount of blood in the heart to the amount of blood pumped out
determinants of stroke volume
- preload
- contractility
- afterload
preload
Force that stretches the relaxed muscle fiber (end-diastolic volume)
>set sarcomere lenght
contractility
cardiac performance at a given preload & afterload
>indicies - rate of pressure development, ejection fraction
>cannot be measured directly so we use parameters
afterload
the load the ventricle faces before it begins to contract
>Force again which the contracting muscle must act
>aortic pressure
>force that must be overcome to eject blood
Frank-Starling “ Law of the Heart”
that stroke volume of the heart increases in response to an
increase in the volume of blood filling the heart when all other
factors remain constant.
why does more blood volume entering the herat improve stroke volume of the heart
more volume means more stretching means sacromeres are closer to their optimal length/postion to contract
cardiac muscle is capable of ___ contractions
> graded (contractions that vary in strength)
syncytium contract
all cardiac msucle fibers contract at the same time
>by additing more Ca2+
cardiac muscle contraction release and uptake of intracellular calcium
figures from slide 12
ejection fraction ho to increase
increase contractility increase ejection fraction
rate of pressure development
rate of pressure with time (dP/dt)
increasing afterload ___ stroke volume
decreases
coronary blood flow function
The blood supply to the heart derives from the right and left
coronary arteries
where do the coronary arteries originate
at the root of the aorta behind
the cusps of the aortic valves
coronary arteries are classified as
Classified as End Arteries – Arteries that do not anastomose (no back up routes),
or have a poorly developed collateral circulation
coronary arteries move around the heart
> artery bifurcates repeatedly into smaller and smaller arteries running on the epicardium
penetrates myocardium and form tee-like network
reaches capillaries (nont tree-like)
arteries in muscle can be ___-
influenced by the contraction of the muscle
right vs left coronary blood flow
-coronary flow increases during diastole
>bigger increase in the left than the right
>left needs to generate more tension to eject blood than the right (higher resistance because radius of blood vessel is collapsing from outside pressures)
heart has _ energy requirements
high
> needs lots of oxygen and nutrients
>ventricular myocardium is packed with mitochondria
the heart has a high _ ratio
oxygen extraction
>organs usually take 25% of oxygen in blood
>heart takes 65-75%
mycardial oxygen transport formula
MOT = coronary blood flow x arterial oxygen content
increase myocardial oxygen demand by increasing ___
myocardial oxygen transport
extravascular compression decreases ____
coronary blood flow during systole
