Peripheral Circulation and Cardiac Output Flashcards Preview

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Flashcards in Peripheral Circulation and Cardiac Output Deck (21):
1

Define compliance

the ability to distend and increase volume due to a pressure increase

2

How do we measure cardiac output?

Output = stroke volume x heart rate

3

What is TPR?

Total peripheral resistance
The sum of all arteriolar resistance

4

Why do we need compliance?

Compliance stores mechanical energy during systole and dissipates it gradually over diastole to dampen the pulsatile nature of the pressure wave.

5

How do we calculate pulse pressure and what is its normal value?

Systolic pressure - diastolic pressure
40mmHg

6

What is the difference between vasodilation and vasodilatation?

Vasodilation: no tonic vasoconstriction
Vasodilatation: offsetting vasoconstriction

7

What happens to TPR if blood demand increases?

TPR decreases

8

If the cardiac output is constant and TPR falls what are the effects?

Arterial pressure falls
Venous pressure rises

9

If TPR is constant but cardiac output rises, what are the effects?

Arterial pressure increase
Venous pressure decrease

10

What does the ventricular compliance curve show?

The relationship between venous pressure and ventricular volume. Increasing venous pressure will increase the amount the ventricles fill.

11

What is Starling's Law of the Heart?

Stretching of the cardiac muscle (increased ventricular filling) increases the binding of actin and myosin and therefore the heart will contract harder.

12

How do we depict Starling's law of the heart on a graph?

Increased EDV/venous pressure increases stroke volume

13

What is contractility?

The efficacy of the heart for each contraction

14

What determines force of contraction?

Contractility
EDV

15

What is meant by the term 'aortic impedance'?

The higher the pressure in the arteries, the harder it is to eject blood.

16

Define preload

The volume of blood in the ventricles at the end of diastole (EDV)

17

Define afterload

The resistance to left ventricle must overcome to circulate blood

18

Why does an increase heart rate become counterproductive after a time?

Increase heart rate shortens the length of diastole therefore the heart does not fill as much and therefore the stroke volume falls. Also, the coronary arteries fill in diastole and if this is shortened they may not get adequate blood supply to perfuse the heart muscle.

19

What is the Bainbridge reflex?

Rise in venous pressure will be sensed in the right atrium
Decreased parasympathetic activity will increase HR to increase cardiac output
Subsides very rapidly

20

If resistance increases, what happens to pressure, energy loss and flow?

Pressure increases
Energy loss increases
Flow decreases

21

What nerve innervates baroreceptors?

Glossopharyngeal nerve (cranial nerve IX)