Cardiovascular System - Lecture 7 Flashcards
What kind of waves does the heart propagate?
un-damped
What happens to colliding waves of the heart?
they block
What was the phenomenon that Mines was exploiting in his experiment?
if you take a chunk of heart muscle out, you will have heterogeneity and some cells will have a slightly longer refractory period than other
How many times does the heart beat per second?
1
How long do the ventricles contract for during a heart beat?
1/3 of the period that the heart contracts
What is the pressure of the ventricle (L or R) compared to the aorta initially when the heart beats?
it is lower
When does the ventricle pressure stop increasing during a heart beat?
until it is greater than the aortic pressure
What happens after the ventricular pressure stops increasing during a heart beat?
the aortic valve opens
What happens to the pressure in the ventricles after the aortic valve opens?
it drops
What are the 5 steps after one of the ventricles beats?
- pressure in the ventricle is lower than the aorta
- pressure in the ventricle increases until it is greater than the aortic pressure
- aortic valve opens
- aortic pressure tracks ventricular pressure
- pressure in the ventricles starts to drop
What is the mean arterial pressure equal to?
100 mmHg
What is the formula for mean arterial pressure?
MAP = diastolic pressure + 1/3 pulse pressure
Why doesn’t the aortic pressure not drop to zero?
because of the Windkessel effect
What is compliance?
how easy it is to stretch out the muscular wall
How much of the cycle do the ventricles contract?
1/3
How much of the cycle is systole?
1/3
How much of the cycle is diastole?
2/3
How much of the cycle do the ventricles not generate pressure?
2/3
Why is the systemic pressure > 0?
due to the Windkessel effect
What is the formula for compliance?
C = change in volume/change in pressure
What does an aneroid sphygmomanometer measure?
the pressure in the cuff
What does an aneroid sphygmomanometer consists of?
a cuff with a bladder
an inflating bulb
a needle valve
an aneroid gauge
What is the difference between an aneroid sphygmomanometer and a mercury sphygmomanometer?
it uses a column of mercury instead
What are the 3 indirect ways to measure blood pressure?
palpation, auscultation, oscillometry
Which artery are you reading the pulse from using the palpation method?
the radial artery
What kind of pressure is found using palpation?
maximum systolic pressure
What are the steps in measuring blood pressure using palpation?
1) Fill cuff until no pulse is detected
2) release pressure (needle valve) slowly
3) When you feel the pulse = Systolic BP
What do you use to measure blood pressure in auscultation?
sounds using a stethoscope
What are you listening for when using auscultation to measure BP?
Korotkoff sounds
What happens to the laminar flow in arteries when blood pressure is taken using auscultation and the cuff deflates?
there is no sound
Why does flow expansion result in turbulence during auscultation?
because there is a flow of blood from a compressed artery to an uncompressed artery
What generates sound in auscultation?
turbulence
What causes tubulence?
the wirls when you let in a bit of blood from a compressed artery to an uncompressed artery
What pressure is heard when you start to hear Korotkoff sounds?
systolic pressure
When do you stop hearing Korotkoff sounds?
when you have laminar flow
What pressure is heard when you stop hearing Korotkoff sounds?
diastolic pressure
What does the machine attached to the cuff sense during oscillometry?
senses the pressure inside the cuff
What does the machine send to the cuff during oscillometry?
pressure waves
Why is blood pressure important?
because we need a pressure gradient on one side of the organ to the other so that blood flows through the capillary network
The perfusion pressure of the arteries is much ___ than the perfusion pressure in the veins
larger
What is flow equal to?
MAP/R
What are the 3 ways we can regulate BP?
1) Adjust flow according to need (e.g. exercise)
2) Keep flow in organs constant despite fluctuations in ‘P’ (“autoregulation”) 3) Minimize fluctuations in Pa (neuro-hormonal control)
What is the total peripheral resitance equal to?
MAP/CO
What is the cardiac output equal to?
HR (heart rate) x SV (stroke volume)
How can we calculate MAP?
CO x TPR
Why does the left ventricle generate a lot of pressure?
because it is very thick and it needs to overcome a large resistance in the systemic circulation
Why does the right ventricle generate less pressure?
because it has a thin wall and needs to do less work to overcome the resistance of the pulmonary arm
When we calculate the pulmonary vascular resistance (PVR), what must we take into account unlike MAP?
pulmonary vein pressure
What is mean pulmonary artery pressure equal to?
15 mmHg
What is pulmonary vein pressure equal to?
5 mmHg
What is pulmonary perfusion pressure equal to?
10 mmHg
Why is PVR«TPR?
because the flow to the lungs is equal to that of the systemic organs
What kind of pressure and resistance does the systemic circulation have?
high pressure, high resistance circulatory system
What kind of pressure and resistance does the pulmonary circulation have?
low pressure, low resistance circulatory system
What happens to ventricles during ventricular systole?
they are contracting
Are the AV valves and aortic/pulmonary valves open or closed during isovolumetric ventricular contraction?
closed
Are the AV valves and aortic/pulmonary valves open or closed during ventricular ejection?
AV valves: closed
aortic and pulmonary valves: open
What happens to the pressure in the ventricles during ventricular ejection?
it increases until the pressure in the ventricles is greater than the pressure in the pulmonary trunk and aorta
Where does blood flow during ventricular ejection?
out of the ventricles
What happens to ventricular contraction and pressure during isovolumetric ventricular relaxation?
ventricular contraction stops and pressure drops
Are the AV valves and aortic/pulmonary valves open or closed during isovolumetric ventricular relaxation?
closed
What happens to the pressure in the aorta and pulmonary trunk during isovolumetric ventricular relaxation?
it remains high due to the Windkessel effect
What happens to the atria during isovolumetric ventricular relaxation?
they have been filling
What happens to the pressure of the ventricles during isovolumetric ventricular relaxation?
it drops to almost 0
Why do the AV valves open during ventricular filling?
because the pressure is lower in the ventricles than in the atria
What do the atria do after the sinus node fires during ventricular filling?
they contract and push a little more blood into the ventricles
Are the AV valves and aortic/pulmonary valves open or closed during ventricular filling?
AV valves: open
aortic and pulmonary valves: closed
What are the 4 steps in the cardiac cycle?
- ventricular filling
- isovolumetric ventricular contraction
- ventricular ejection
- isolvolumetric ventricular relaxation
Wiggers diagram shows phases for which side of the heart?
left heart
Why does aortic pressure spike in Wiggers diagram?
due to ventricular contraction
During the filling phase, the pressure in the left ventricle is slightly ___ than the left atria.
lower
During the filling phase, is the mitral valve open or closed?
open
What does the P-wave represent during the filling phase?
depolarization of the atria
What happens to the atrial pressure during the P-wave?
it increases
What happens to the AV valves during the P-wave?
they open
Where does blood move when the AV valves open?
to the ventricles
What happens to the ventricles during the QRS complex?
they are depolarized
What happens to the pressure of the ventricles during the QRS complex?
they increase
What happens to the volume of blood in the ventricles during isovolumetric ventricular contraction?
it remains the same
What happens to all the valves when ventricles contract?
they close
Why does the semilunar valve open?
to send blood to the aorta from the ventricle
Why is the pressure in the ventricles greater than the aortic pressure during ventricular ejection?
because you need enough pressure in the ventricle to overcome the pressure in the aorta to push blood
What happens to the ventricular volume once the blood in the ventricle is pushed out to the rest of the body?
it decreases
What happens to the ventricle during the T-wave?
it repolarizes
What happens to the ventricular pressure during the T-wave?
it decreases
What happens to the valves during isovolumetric ventricular relaxation?
they close
What happens to the pressure in the ventricles during isovolumetric ventricular relaxation?
it drops
When does ventricular filling happen?
once ventricular pressure drops below atrial pressure
What happens to the AV valve once the ventricular pressure drops below the atrial pressure?
it opens
Where does the 1st heart sound happen?
at the QRS complex
Why do we hear the first heart sound?
because the AV valve is closing due to the ventricles contracting
When does the 2nd heart sound happen?
after the T-wave
Why do we hear the second heart sound?
because the aortic valve is closing
What happens to the right heart during the cardiac phases?
the same events as the left heart but with lower pressures
What is stroke volume equal to?
120mL–50mL=70mL
What is the formula for stroke volume?
end diastolic volume(EDV) – end systolic volume(ESV)
What is the formula for ejection fraction?
stroke volume (SV) / end diastolic volume (EDV)
What is ejection fraction equal to?
70 mL/120 mL = 0.6 or 60%
What is the formula for cardiac output?
heart rate (HR) x stroke volume (SV)
What is cardiac output equal to?
70 b/min x 70 ml = 4900 mL min (5L / min)
(T or F) The ventricle generates pressure over the duration of the cardiac cycle
False! - it only generates pressure over about 1/3 of the cycle. The rest is due to the Windkessel effect
(T or F) The Windkessel effect generates pressure over the cardiac cycle except during the contraction of the ventricle.
False! Systole starts the instant that the ventricle contracts. There is a period of isovolumetric ventricular contraction when the aortic valve is closed, and no pressure is generated by the ventricle in the aorta.
(T or F) The BP measures of palpation, auscultation and oscillometry measure the same thing in different ways.
False! While they all can estimate systolic pressure, only auscultation and oscillometry measure diastolic pressure.
(T or F) A patient has a muscle twitch in their bicep. This might give abnormal readings using an automated BP machine, but not using the stethoscope method.
True! The cuff pressure in the oscillometry measure is used to estimate BP. Twitches in the muscle would change the cuff pressure, but wouldn’t affect the Korotkoff sounds, which are downstream. But this is just a guess! – the manufacturers probably have algorithms in place to counter this.
The two valves of the left ventricle are either open or closed. There are 4 possible ways the valves can present: (closed, closed), (open, closed), (closed, open) or (open, open), and each defines a phase. Is this true?
False! The two valves are never open at the same time. Blood would flow in the wrong direction!
