Physiology 4 - Control of Cardiac Output Flashcards Preview

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Flashcards in Physiology 4 - Control of Cardiac Output Deck (25)
1

State the relationship between length of sarcomere and tension.

At the shortest and longest length of sarcomere, tension is 0, but reaches a peak in between the two

2

What is the primary mechanism by which stroke volume can be increased?

Increase end diastolic volume

3

How is the blood able to continue moving round the body, even when the ventricles are in diastole?

The aorta has excessive elastic tissue, meaning it can swell and almost pump blood itself round the body

4

What happens to the pressure in the aorta if the volume increases?

The pressure increases

5

What is meant by saying veins are very 'compliant'?

You can put a large volume of blood through a vein, without a large change in pressure

6

How would you calculate the mean arterial blood pressure (MABP)?

Diastolic pressure + 1/3 Pulse pressure

7

How is pulse pressure calculated?

Systolic pressure - Diastolic pressure

8

Why can't you just take the halfway point of systolic and diastolic pressure when calculating the MABP?

The ventricles are in a diastolic state for much longer than they are in a systolic state

9

List some factors that can affect flow of blood from the heart.

Viscosity
Radius of vessel
Length of vessel

10

How is arterial pressure calculated?

Cardiac Output x Total Peripheral Resistance (V = IR)

11

How is CO calculated?

HR x SV

12

How is the stroke volume calculated?

The difference between EDV and ESV

13

What effect does an increase in venous return have?

Increased EDV
Increased ejection fraction

14

What effect does increased EDV have on force of contraction?

Increase - Frank-Starling mechanism

15

What is the preload?

Venous pressure and venous return to the heart

16

What is the afterload?

The aortic/PA pressure

17

With regard to 'force', what does Frank-Starling's Law of the Heart state?

Active force = total force - resting force

18

What does inotropic mean?

Modifying the force or speed of contraction of muscles

19

Increasing the sympathetic activity has an inotropic effect. What is this effect and how does it affect the appearance of a length-tension curve?

+'ve inotropic effect
Make the length-tension curve steeper gradient and much greater tension

20

How does oscillation in BP decrease as blood nears capillaries from arteries and arterioles?

Vessels are less elastic

21

What two factors decrease compliance?

Age
Vasoconstriction

22

How is flow calculated?

Change in Pressure/Total peripheral Resistance (TPR)

23

How is arterial pressure calculated?

CO x TPR

24

What are normal systemic and pulmonary pressures?

120/75
26/8

25

What factor affects the magnitude of pulse pressure

Stroke Volume

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