lecture 5: chapter 14/15 Flashcards
where is blood pressure on the circulatory system the highest
in the aorta and largerer arteries
trtue or fals: the pressure stays constant at the aortat
true (relattively contanst)
Why does the pressure drop significantly at the arteriole/capillary junction
They sre area of high resistances
Allows velocity to slow for echange
true or false: the pressure in the systetmoc circulation stays constant throughout the enttire passave
false, it decrases until it is at the lowst velocity and prssure near the capillaries
when the blood returns in the right atrium the pressure is 0 mmHH
true
where are there lower pressure, arteriol orvenous side
venous side
what is perpherial ressitance
the friction between the blood and vessel wall
what is the main determinant of resistance
radius
where is flow faster, larger or smaller vessels
faster in large
explain why a smaller radius means a higher resistance
because there an increased surface area exposed to blood which will increase resistance (look at slie 3 from 14/15)
what is the relationship between resistance and radius
if you increase radius, flow is 16x greater (flow=r4)
Resistamce decreases 4 fold (resistance=1/r4)
what are some ecamples of things that increase resistance
abrupt chagnes in diametter, fatty plaques from atherosceleoriss, braching, or sharp turns
what do abrupt changes in direction, fatty plaquest etc do in tterms of restitsncae
increase resistance and disrup laminar flow and cause turnbeunce flow
what is turbulent flow
irregular fluid motion tthat icreases resistance
explain why people with heart plaque have hypertension
because plaque causes bluid up in arterires with increases resistance and ie need more pressure to overcome
explain laminar flow
during laminar flow all the vectors flow in parallel with the highestt velocity and and least friction in the center of the vessek
what are the 3 main determinatns of resisance
blood viscocity
vessel lengtth
vassel radius
blood is more visouc in whatt season and gender
in men and summer
what is poiseuilles law
flow= (pie)(delta pressure)(radius)^/8nl
what does conductance mean
how easy is is to move blood from point a tob
what is the formular for conductance
1/resistance
what is the problem with circualtion in series
the flow is affected by all resisatnces
where is an area in the body where blood flows in series
in the pulmonary circulation (from heart, to lungs and back to heart)
what is imporant about circulation in parallel
it is imporatnt for how the body regulates where the blood is going in the body
it allows for seperatet resistance paths
what is the difference between Q and F
Q is the flow through the entire circulation
F is the flow through a certain segmaent
what is the formula for flow
q=pressure/resistance
what is the flow through a blood vessel determined by
1) the pressure difference between the two ends of the vessel
2) the resistance of the vessel
if pressure increases (and resistance is constant) what happens to the flow
it increases
if resisttance increases (and pressure is constant) what happens to the flow
flow decreases
the diastolic pressure is taken at the end of
the resting phase when the aortic valve opens
after ventricular ejecttion and pressure is decreases, why does it start to increase again
insicura
increase in pressure die tto tthe bouncing off of the peripheral resistance
=imporatant for filling coronary arteries
when the left ventricle contrtacts… more or less blood enters into arteriak system
more blood enters the arterial system than gets pushed onwards
what does the fact that more blood enters the arteiral system than gets oished out when the elft ventricle contrcatcts causes what
causes arteries to strettch and pressure within them rises
the highest pressure in the aorta is called..
systolic
what happens when the left ventricle relaxes (in terms of recoil)
the stretched arterial walls recold and push the contained blood onwards through the system
what pushes blood onwards into the circualtory system
the elastic recold of the arteries (compliace)
as the arteries recoil what happens to the blood and pressure
the amount of blood contained decreases and as does pressure
the lowest pressure acheived just before the next contraction is called…
diastolic pressure
what does aterial complicance mean
the ability to expand and recoil
“a change in pressure will affect a change of volume)
what is the fomrular for arterial compliace
compliance=change on volume/change in pressure
the walls of which vessel are stronger
arteries stronger than veins
which vessel has a thicker oUTER layer but less muscle
veins
which vessel has thicker walls and how
ateries are more rigid because they have more smooth msucle
the arteries are less or more distensible than the veins
less
the arteries are blank times less distensible than the veins
8 times less
an increase in pressure causes 8 times as much incrase in blood in a blank
in a vein as in an artery of comparible size
if a vein and artery are both subjected to 100 mmHG, how mich volume will be in the artery vs vein
artery: 1o0 ml
vein 800 ml
what is the reason the veins can hold more blood given the same pressure increase as a artery
because of their looser wall (with less smooth muscle), they are more distensible and compliant allowing more blood
which vessels are known as the capacitance vessels and why
veins since they are the ones that hold the blood
what does vascular distensibility mean
is the fracntional increase in volume for each mmHG rise in pressure
veins are more or less distensible than arteries
8 times more distensible
which arteries are knoen to be relatively distensble
pulmonary
what is the formula for vascular distensibility
VD= increase in volume/(icnrease in pressure)(orginal volume)
true or false : vascular distensibility isnt imporant for circualtory function
it plays an imprtant role
what does the distensible nature of the arteries allow
allows them to accomodate the pulsatile output fo the heart and to average out the pressure pulsations
]
=provides smooth continous flow of blood thorugh the very small blood vessels and tissues
explain how vascular distensibility allows pulsatile to go to continous
every time a larger vessel expands and recoil it is able to flatten and dampen the pulsatile flow
-=spme of the energy stored in the wall as kinetic becaomes potential aand the pressure goes forward instead of laterally
what is vascular capitance
the total capacitance of blood that can be stored in a given portion of the ciruclation for each mmHG
what is the formula for capacitance
distensibility x volume
even slight increases in venous pressures cause what
cause veins to store 0.5-1 litre of ecta blood
if there is a slight increase in pressure what does that mean veins can provide
provide a resevoir function for storing large quantities of extra blood that can be called into use whenever requred elsewhere in circualtion
true or false: the arteries serve as a resservoive for storing blood
false, the veins
the capacitance of the veins is smaller or higher than the arteries
the capacitance of veins is 24 times that of the arteries
any given change in volume within the arterial tree results in…
larger increase in pressure than in veins
what happens to the blood when veins do vasoconstriction
large quantities of blood are tranferred to the heart, therby increasing cardiac output due to an icnrease in venous return (because compliance)
=more blood comes in
what is the formuka for pulse pressure
Sys. BP-diastolic BP
what are the 2 advantages of distensibiliy and compliace
1) saving energy for the heart
2) pulsatile flow to continuous
in the pressure curve, why do we get an elongated tail and why is that beneficial
elongated tail because of the compliance (the recoil propel th blood forward so it saves work for the heart)
what is the “ohms law” for circualtion
q=delta p/r
CO is the …
flow
what are the two sources of the pressure
mean arterial pressure and central venous pressure
what is the source of resistance in the body
systemic vascular retsiantce
KNOW THE LAST TWO SLIDES
