peripheral resistance and blood pressure Flashcards
Q proportional to
P
pressure gradient
Q= flow
Q inversely proportional to
R
resistance
Q =
Delta P/R
Q =
longer equation
delta P x (Pi r^4)/(8L x n)
n= eta , viscosity of fluid
L, length of vessel
r is radius
Q is
flow
CO in L/min
P units
mmHg
blood flows in what direction
high to low pressure
BP=
CO x PR
flow independent of
absolute pressure
P1
difference in pressure is the important part
why doesn’t length control blood flow in the body
it is constant
length of vessels doesn’t change
longer tube
more resistance, less flow
higher viscosity
more resistance, less flow
does viscosity control blood flow in the body
no, stays constant under physiological conditions
why would viscosity increase
dehydration
higher altitude, increased tbc production
EPO increasing
what is most important factor in determining flow
radius
decr radius
increased friction of fluid against vessel wall
reducing radius two fold..
decreases flow 16x
how to regulate radius
smooth muscle
total peripheral resistance mainly regulated by
arterioles
total peripheral resistance is
and determines
sum of resistance in all blood vessels
blood pressure
arterioles recap
thin muscular walls
regulate BP and flow to organs
largest drop in pressure is within the
arterioles
radius in the arterioles determines
blood flow to individual organs
smooth muscle relaxation and contraction controls which organs blood flowing to and how much
at rest most blood going to which organ?
abdominal organs
canniulation
measures BP
not very practical
measure pressure with transducer
measuring arterial pressure
sphygmomanometer
with stethoscope and cuff
non invasive
korotkoff sounds sequence
no sounds: cuff pressure above systolic pressure. artery shut
cuff pressure just below systolic pressure: first sounds, soft tapping, intermittent
sounds loud, tapping and intermittent
low muffled sound lasting continuously
cuff pressure below diastolic pressure , this vessel always open, no sound
this is as cuff pressure decreases
high cuff pressure
no sounds, artery is closed
middle cuff pressure
sounds heard
artery opening and closing
low cuff pressure
no sounds
artery open
where should the cuff be
at level of the heart
pulse
vibration of arteries caused by ejection of blood from the heart from left ventricle
2 places you can feel your pulse
radial artery (wrist) cartoid artery ( neck)
pulse pressur
difference between systolic and diastolic pressure
mean pressure
average pressure over the cycle
as diastole twice as long
how is MAP often measured
DP + 1/3 PP (pulse pressure)
is bp influenced by height
yes
Pressure difference =
height x density x gravity
height most important because density and gravity stay same
standing
increased pressure of MAP in legs lead to pooling of blood in the veins feet swelling on flights pressure in head lower than feet fainting
flat
pressure in head almost same as feet
hypertension
high bp
often don’t know cause
high bp can lead to
heart attack: rupturing of coronary arteries
stroke : rupturing of blood vessels to brain
kidney failure, heart failure
