cardiovascular - lecture 7

Question 1

describe refractories

Answer 1

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

Question 2

once a sec lv beats and what happens - 6 steps

Answer 2

1. The pressure is initially lower than in the aorta
2. It increases until the ventricular pressure is greater than aortic pressure
3. The aortic valve opens
4. The aortic pressure then tracks ventricular pressure
5. Pressure in ventricles starts to drop
6. Aortic valve closes

Question 3

once a sec lv beats and what happens - gen

Answer 3

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

Question 4

what is map

Answer 4

mean arterial pressure
diastolic pressure + 1/3 pulse pressure = 100mmhg

Question 5

describe windkessel effect gen

Answer 5

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

Question 6

describe windkessel effect specific

Answer 6

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

Question 7

describe direct measure of bp

Answer 7

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

Question 8

name indirect measures of bp

Answer 8

palpation
ascultation
oscillometry

Question 9

describe indirect measures

Answer 9

vacuum chamber = pump air pressure here same as bladder
cuff around arm that expands with bladder
bulb that inflates

Question 10

how to measure indirectly - sphygmomanometers

Answer 10

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

Question 11

describe palpation

Answer 11

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

Question 12

steps of palpation

Answer 12

A 1) Fill cuff until no pulse is detected
2) release pressure (needle valve) slowly
3) When you feel the pulse = Systolic BP

Question 13

describe ascultation

Answer 13

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

Question 14

describe oscillometry

Answer 14

senses pressure inside cuff
korotcoff sounds
characteristic shape

Question 15

why is bp important

Answer 15

for perfusion of organs
flow is around equal to map/r

Question 16

bp regulation = 3 ways

Answer 16

adjust flow according to need like exercise
keep flow in organs constant despite fluctuations in p - autoregulation
minimize fluctuations in pa = neuro hormonal control

Question 17

what is map equal to

Answer 17

map = co x tpr (total peripheral resistance)
map = hr x sv x tpr

Question 18

describe pulmonary vascular resistance

Answer 18

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

Question 19

describe systemic vs pulm circ

Answer 19

sytemic = high pressure, high resistance
pulmon = low pressure, low resistance

Question 20

describe cardiac cycle = ventricular systole - phase 1

Answer 20

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

Question 21

describe cardiac cycle = ventricular systole - phase 2

Answer 21

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

Question 22

describe cardiac cycle = ventricular diastole - phase 1

Answer 22

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

Question 23

describe cardiac cycle = ventricular diastole - phase 2

Answer 23

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

Question 24

what is wiggers diagram

Answer 24

phases for left heart

Question 25

describe filling phase - wiggers

Answer 25

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

Question 26

describe isovolumetric contraction phase

Answer 26

ventricle pressure exceeds that of aorta - aortic valve opens

Question 27

describe ejection phase

Answer 27

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

Question 28

describe isovolumetric relaxation

Answer 28

ventricle pressure drops lower than the pressure in atrium - almost 0
mitral valve opening = ventricle filling phase = then repeat all pahses

Question 29

what is first and second heart sound

Answer 29

first = mitral valve closing
seconds = aortic valve closing

Question 30

what happens in right heart - wiggers

Answer 30

parallel events happen synchronously in right heart. Heart sounds include closing of tricuspid and pulmonary valves.

Question 31

what is stroke vol

Answer 31

end diastolic vol - end systolic vol
120-50=70ml

Question 32

what is ejection fraction

Answer 32

stroke vol/end diastolic vol
= 70/120=60%

Question 33

what is cardiac output

Answer 33

heart rate x stroke vol
70b/min x 70ml = 5l/min