Cardiovascular Physiology

Question 1

Define cardiac output

Answer 1

Is the blood pumped in one minute. It sets how efficiently the heart can meet the body’s demands for the maintenance of adequate tissue perfusion.
The volume in healthy adult is 4 to 6L at rest and can increase from 4 to 6 times.

Question 2

What is the formula used to calculate the cardiac output ?

Answer 2

Q=SV x HR

Where : Q is the cardiac output, SV the stroke volume and HR the heart rate

Question 3

Which factors can influence the heart rate ?

Answer 3

Autonomic innervation
Hormones
Fitness level
Age

Question 4

Which factors can influence the stroke volume ?

Answer 4

Heart size
Fitness level 
Gender 
Contractility 
Duration of contraction 
Preload 
After load

Question 5

How do we calculate maximum heart frequency ?

Answer 5

Max HR = 200-age

Question 6

What is the average stroke volume in healthy adults ?

Answer 6

70ml

Question 7

Give one way to increase cardiac output in a healthy way ?

Answer 7

By increasing the heart frequency

Question 8

What is the maximum volume of blood that the heart can contain ?

Answer 8

120 ml of blood

Question 9

How much blood fills the heart permanently ?

Answer 9

Cardiac output average = 70 ml
Maximal volume that heart can contain = 120 ml

Therefore blood permanently filling the heart = 50 ml

Question 10

When is the heart relaxed ?

Answer 10

At the end of diastole

Question 11

What is the end diastolic/ systolic volume ?

Answer 11

End diastolic volume = 120 ml

End systolic volume = 50 ml

Question 12

Describe the cardiac cycle

Answer 12

Systole : contractile phase, ejection phase => end systolic volume = 50 ml
Diastole : relaxation phase, filling phase => end diastolic volume = 120 ml

Question 13

What is the formula to calculate stroke volume

Answer 13

SV = EDV - ESV

Question 14

Define ejection fraction

Answer 14

Is used as a mesure of the pumping efficiency of the heart and is used to classify heart failure
It’s also the fraction of total blood volume ejected from the left ventricle during each contraction
EF = SV / end diastolic volume x 100
EF= 70 / 120 x100 ca 60%

Question 15

What is the Frank-Starling’s law ?

Answer 15

States that there is a correlation between the ejection fraction and the filling of the heart
Ex : increase stretch of cardiac muscle will trigger increased force of contraction and increase stroke volume