CVS Session 6- Control Of Cardiac Output

Question 0

What happens to venous and arterial pressure if TPR rises?

Answer 0

Venous pressure decreases

Arterial pressure increases

Question 1

What happens to the venous and arterial pressures if TPR falls?

Answer 1

Venous pressure rises

Arterial pressure decreases

Question 2

What happens to arterial and venous pressure if the cardiac output rises?

Answer 2

Arterial pressure rises

Venous pressure decreases

Question 3

What happens to arterial and venous pressure if cardiac output falls?

Answer 3

Arterial pressure decreases

Venous pressure increases

Question 4

Why does venous pressure rise when arterial pressure and cardiac output are low?

Answer 4

Because less blood is being pumped out of the heart and therefore back to the heart. For this little blood to return to the heart, high pressure is required so it can reach it.

Question 5

What is the relationship between TPR and the body’s demand for blood?

Answer 5

They are inversely proportional

Question 6

What is demand-led pumping?

Answer 6

The response of the heart to arterial and venous pressures to bring the pressures back to normal.

Question 7

What is the pressure response after a meal if cardiac output is constant?

Answer 7

• gut needs more blood
• local vasodilators dilate arterioles
• TPR falls
• arterial pressure falls and venous pressure rises

Question 8

When does the heart fill?

Answer 8

Diastole

Question 9

What is the stroke volume?

Answer 9

The difference between the end systolic volume and the end diastolic volume

Question 10

When do the ventricles stop filling?

Answer 10

When the walls have stretched enough to cause an intraventricular pressure which is equal to the venous pressure.

Question 11

What is the relationship between venous pressure and ventricular filling?

Answer 11

The higher the venous pressure, the more the ventricles will fill (within limits)

Question 12

If venous pressure increases, what happens to the stroke volume?

Answer 12

It increases

Question 13

What is “pre-load” and what is it determined by?

Answer 13

It is the end diastolic stretch of myocardium.

Determined by the venous pressure

Question 14

What is “after-load” and what does it determine?

Answer 14

It is the force necessary to expel blood out of the heart into the arteries during systole.
It determines what happens during systole

Question 15

What is starling’s law?

Answer 15

Increases in venous pressure will lead to an increased stroke volume (within limits).
More in=more out

Question 16

On the Starling curve, why does the stroke volume only increase to a certain point with venous pressure?

Answer 16

Due to the constraints of the pericardium- the heart can only fill to a certain point.

Question 17

What factors lead to an increased stroke volume? (4)

Answer 17

• increased venous pressure
• a fall in TPR
• increased sympathetic activity
• decreased arterial pressure

Question 18

What is contractility?

Answer 18

It is the relationship between force of contraction and venous pressure, for any given fibre length.

Question 19

What is the end systolic volume?

Answer 19

The amount that the ventricle empties

Question 20

What does the end systolic volume depend on?

Answer 20

• how hard it is to eject blood from the ventricles

- how hard they contract

Question 21

What is force of contraction determined by?

Answer 21

• end diastolic pressure

- contractility

Question 22

If arterial pressure falls, what will happen to the end systolic volume and stroke volume?

Answer 22

End Systolic volume - fall

Stroke volume - increase

Question 23

What is the function of a baroreceptor?

Answer 23

To detect changes in arterial pressure.

Question 24

What is the consequence of a fall in arterial pressure?

Answer 24

Increased heart rate, stroke volume and contractility

Question 25

When arterial pressure is low, how is heart rate increased?

Answer 25

Reducing parasympathetic activity

Increasing sympathetic activity

Question 26

When arterial pressure is low, how is contractility increased?

Answer 26

Increasing sympathetic activity

Question 27

What is the Bainbridge reflex?

Answer 27

If venous pressure rises, heart rate rises because venous pressure in the right atrium is detected and parasympathetic activity is reduced.

Question 28

When does cardiac output rise? (2)

Answer 28

• when venous pressure rises

- when arterial pressure falls