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)