lecture 5: chapter 14/15 Flashcards
where is blood pressure on the circulatory system the highest
in the aorta and largerer arteries
true or false: the pressure stays constant at the aorta
true (relatively constant)
Why does the pressure drop significantly at the arteriole/capillary junction
They are area of high resistances
Allows velocity to slow for exchange
true or false: the pressure in the systemic circulation stays constant throughout the entire passage
false, it decreases until it is at the lowest velocity and pressure near the capillaries
when the blood returns in the right atrium the pressure is 0 mmHH
true
where are there lower pressure: arteriol or venous side?
venous side
what is peripheral resistance
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 slide 3 from 14/15)
what is the relationship between resistance and radius
if you increase radius, flow is 16x greater (flow=r4)
Resistance decreases 4 fold (resistance=1/r4)
what are some examples of things that increase resistance
abrupt changes in diameter, fatty plaques from atherosclerosis, branching, or sharp turns
what do abrupt changes in direction, fatty plaques etc do in terms of resistance
increase resistance and disrupt laminar flow and cause turbulence flow
what is turbulent flow
irregular fluid motion that increases resistance
explain why people with heart plaque have hypertension
because plaque causes build up in arteries with increases resistance and ie need more pressure to overcome
explain laminar flow
during laminar flow all the vectors flow in parallel with the highest velocity and and least friction in the center of the vessels
what are the 3 main determinants of resistance
blood viscosity
vessel length
vessel radius
blood is more viscous in what season and gender
in men and summer
what is poiseuille’s law
flow= (pie)(delta pressure)(radius)^/8nl
what does conductance mean
how easy is is to move blood from point a to b
what is the formula for conductance
1/resistance
what is the problem with circualtion in series
the flow is affected by all resistances
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 important for how the body regulates where the blood is going in the body
it allows for separate 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 resistance 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 ejection and pressure is decreases, why does it start to increase again
incisura
increase in pressure due to the bouncing off of the peripheral resistance
= important for filling coronary arteries
when the left ventricle contracts… more or less blood enters into arterial system
more blood enters the arterial system than gets pushed onwards
what does the fact that more blood enters the arterial system than gets pushed out when the left ventricle contracts cause what
causes arteries to stretch 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 recoil and push the contained blood onward through the system
what pushes blood onwards into the circulatory system
the elastic recoil of the arteries (compliance)
as the arteries recoil what happens to the blood and pressure
the amount of blood contained decreases and as does pressure
the lowest pressure achieved just before the next contraction is called…
diastolic pressure
what does arterial compliance mean
the ability to expand and recoil
“a change in pressure will affect a change of volume)
what is the formula for arterial compliance?
compliance=change in 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
arteries are more rigid because they have more smooth muscle
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 increase 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 much volume will be in the artery vs vein
artery: 100 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 fractional increase in volume for each mmHG rise in pressure
veins are more or less distensible than arteries
8 times more distensible
which arteries are known to be relatively distensible
pulmonary
what is the formula for vascular distensibility
VD= increase in volume/(increase in pressure)(original volume)
true or false : vascular distensibility isnt imporant for circualtory function
false,it plays an important role
what does the distensible nature of the arteries allow
allows them to accommodate the pulsatile output of the heart and to average out the pressure pulsations
=provides smooth continuous flow of blood through the very small blood vessels and tissues
explain how vascular distensibility allows pulsatile to go to continuous
every time a larger vessel expands and recoil it can flatten and dampen the pulsatile flow
-=some of the energy stored in the wall as kinetic becomes potential and the pressure goes forward instead of laterally
what is vascular capacitance
the total capacitance of blood that can be stored in a given portion of the circulation 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 extra blood
if there is a slight increase in pressure what does that mean veins can provide
provide a reservoir function for storing large quantities of extra blood that can be called into use whenever required elsewhere in circulation
true or false: the arteries serve as a reservoir 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 transferred to the heart, thereby increasing cardiac output due to an increase in venous return (because of compliance)
=more blood comes in
what is the formula for pulse pressure
Sys. BP-diastolic BP
what are the 2 advantages of distensibility and compliance
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 the blood forward so it saves work for the heart)
what is the “ohms law” for circulation
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 resistance
KNOW THE LAST TWO SLIDES
