cardiovascular - lecture 7 Flashcards
describe refractories
heart = dynamical active system (excitable media)
propagate undamped waves
colliding waves block - cell refractory
also true for neurons but they have refractory time of a few ms
myocytes refractory time 100-300ms depends on cell tyoe
like cannot reignite after fire = nothing left to burn
once a sec lv beats and what happens - 6 steps
- The pressure is initially lower than in the aorta
- It increases until the ventricular pressure is greater than aortic pressure
- The aortic valve opens
- The aortic pressure then tracks ventricular pressure
- Pressure in ventricles starts to drop
- Aortic valve closes
once a sec lv beats and what happens - gen
ventricles contract for 1/3rd of time
lower then higher = opens valve
stays high 120/80 but ventricle only generates pressure briefly
aortic pressure doesnt drop to 0
what is map
mean arterial pressure
diastolic pressure + 1/3 pulse pressure = 100mmhg
describe windkessel effect gen
air gets compressed and energy released = dampens force
elastic arteries act like elastic and push down = provides pressure
keeps power in system
stores energy in capacitor
describe windkessel effect specific
in 1/3 of cycle (systole) ventricle contracts
for other 2/3rds of cycle - diastole = no pressure generated by ventricle
systemic pressure is >0 than due to windkessel effect
compliance = delta vol / delta pressure so delta p = delta v /compliance
describe direct measure of bp
Volume (V)= area x height = Ah
Mass (m) = density(p) x volume = pV=pAh Force (F) = m x acceleration (g) = mg=pAhg Pressure(P)= force/area = F/A= pgh
SI Units: newtons/m2
But usually given in cmH20, or mmHg for BP.
1 cm Hg= 14 cm H20, 280cm H2O = 200 mmHg
(liquid’s height in the tube doesn’t depend on A)
measure height in tube
name indirect measures of bp
palpation
ascultation
oscillometry
describe indirect measures
vacuum chamber = pump air pressure here same as bladder
cuff around arm that expands with bladder
bulb that inflates
how to measure indirectly - sphygmomanometers
Aneroid Sphygmomanometer: Consists of a cuff with a bladder, an inflating bulb, a needle valve and an aneroid gauge
Mercury Sphygmomanometer:
Same as above, but used a column of mercury
describe palpation
use hand to sense pressure
radial artery = should feel pulse
pressure high enough so no blood through
pulse pressure > cuff pressure and blood gets through = pressure close to max = systolic arterial pressure
have to release slowly since many errors
steps of palpation
A 1) Fill cuff until no pulse is detected
2) release pressure (needle valve) slowly
3) When you feel the pulse = Systolic BP
describe ascultation
heart sounds
listen for korotkoff sounds
flow expansion results in turbulence - turbulent flow heard - when have laminar flow = no sounds
laminar flow in arteries = no sound when cuff deflated
when hear sound = systolic, equal to cuff pressure- but higher
laminar flow = no sound = diastolic pressure
describe oscillometry
senses pressure inside cuff
korotcoff sounds
characteristic shape
why is bp important
for perfusion of organs
flow is around equal to map/r
bp regulation = 3 ways
adjust flow according to need like exercise
keep flow in organs constant despite fluctuations in p - autoregulation
minimize fluctuations in pa = neuro hormonal control
what is map equal to
map = co x tpr (total peripheral resistance)
map = hr x sv x tpr
describe pulmonary vascular resistance
mean pulmonary artery pressure = 15mmmhg
pulmonary veing pressure = 5mmhg
unline map - cannot discount pulm bein pressure as error 30%
pulmonary perfusion = 10 mmhg
but flow to lungs equal to that of systemic organs
pvr«tpr
massive change in resistance
left ventricle = thick, big pressure, differnce to overcome large resistance in systemic circd
describe systemic vs pulm circ
sytemic = high pressure, high resistance
pulmon = low pressure, low resistance
describe cardiac cycle = ventricular systole - phase 1
isovolumetric ventricular contraction
10ms after systole starts
av vales open at start of contraction
heart contracts = av valves close
pressure increases but both valves closed so vol doesnt change
iso = single vol
describe cardiac cycle = ventricular systole - phase 2
ventricular ejection
pressure increases untill pressure in ventricles greater than pressure in pulmonary trunk and aorta
pulmonary and aortic valves open
blood flows out of ventricles into both circulations
ventricle pressure peaks and starts to fall
describe cardiac cycle = ventricular diastole - phase 1
isovolumetric ventricular relaxation
ventricular contraction stops and pressure drops
aortic and pulmonary vlaves close = pressure in aorta and pulm trunk remain high due to windkessel effect
soon as valves close - enter phase of ventricular relaxation with no change in ventricular vol
pressure drops to almost 0
atria have been filling
describe cardiac cycle = ventricular diastole - phase 2
ventricular filling
pressure lower in ventricles than atria
av valves open
sinus node fires
fill ventricles
atria contract and push little more blood into ventricles = atrial kick
what is wiggers diagram
phases for left heart
describe filling phase - wiggers
aortic pressure = spikes due to ventricular contraction, falls slowly due to windkessel effect
from beginning of diastole ventricles fill = pressure in left ven lower than left atria, mitral valve open, small diff in pressure is enough to mostly fill ventricle
p wave = have atrial contraction, atrial kick - a little extra blood to ventricle, most of filling occurs when there is no contraction of either atria or ventricles
qrs = pressure in left ven increases, pressure in ventricule higher than atria, about 10ms, after contraction starts, mitral valve closes aortic already closed
pressure continues to increase
describe isovolumetric contraction phase
ventricle pressure exceeds that of aorta - aortic valve opens
describe ejection phase
pressure in ventricle continues to increase
pressure in aorta increases = just under ventricular pressure
at peak = ventricles start to relax, pressure still high but falling, soon aortic is greater than ventricular so aortic valve closes
pressure in ventricles dropd to almost 0
all valves closed
describe isovolumetric relaxation
ventricle pressure drops lower than the pressure in atrium - almost 0
mitral valve opening = ventricle filling phase = then repeat all pahses
what is first and second heart sound
first = mitral valve closing
seconds = aortic valve closing
what happens in right heart - wiggers
parallel events happen synchronously in right heart. Heart sounds include closing of tricuspid and pulmonary valves.
what is stroke vol
end diastolic vol - end systolic vol
120-50=70ml
what is ejection fraction
stroke vol/end diastolic vol
= 70/120=60%
what is cardiac output
heart rate x stroke vol
70b/min x 70ml = 5l/min
