24 - Cardiac Function and Control

Question 1

For any volume of blood, pressure depends on 1) 2)

Answer 1

1) Compliance of the wall 2) Active tension in the wall

Question 2

When is compliance important in blood pressure?

Answer 2

Diastole

Question 3

When is active pressure important in blood pressure?

Answer 3

Systole

Question 4

Is the right or left ventricle less compliant?

Answer 4

The left is thicker and therefore less compliant than the right

Question 5

Which ventricle can generate more force?

Answer 5

The left

Question 6

If more blood is pumped into the arterial system, what occurs in the venous system?

Answer 6

There is less blood

Question 7

When can the pericardium become an important determinant of ventricular compliance?

Answer 7

When it stiffens (EG: inflammation, TB, pericarditis, cancers)

Question 8

Normal end systolic volume

Answer 8

Between 65-150mL, but this can vary

Question 9

Diastolic left ventricle pressure-volume curve

Answer 9

Question 10

Systolic left ventricle pressure-volume curve

Answer 10

Question 11

Normal total cardiac output

Answer 11

~5L/min

Question 12

Normal stroke volume

Answer 12

~150mL

Question 13

Normal early diastolic pressure

Answer 13

~5mmHg

Question 14

How is a Frank Starling curve generated?

Answer 14

Fill left ventricle with blood, don’t let blood escape. As volume increases, with the same electric stimulation the ventricular pressure increases (due to increased force of contraction)

Question 15

Ways to increase stroke volume 1) 2) 3)

Answer 15

1) Decrease heart rate 2) Increase end diastolic volume 3) Increase ventricular contractility

Question 16

Frank Starling relationship

Answer 16

More stretch = more tension More end diastolic volume = more stroke volume

Question 17

What does increased stroke volume reflect?

Answer 17

Increased LV pressure

Question 18

What effect does increased heart rate have on stroke volume?

Answer 18

Decreased stroke volume (as lower end systolic volume)

Question 19

Why can the heart appear smaller with exercise?

Answer 19

When heart rate increases, stroke volume decreases, as the time for diastole shortens (leads to decreased end diastolic volume)

Question 20

Effect of increased heart contractility on LV pressure and volume

Answer 20

Question 21

Mitral valve location

Answer 21

Between left atrium and left ventricle

Question 22

Effect of acidosis on heart function

Answer 22

Impairs heart function

Question 23

Effect of increased sympathetic stimulation on heart contractility

Answer 23

Increases contractility

Question 24

Effect of parasympathetic activity on heart contractility

Answer 24

Parasympathetic nervous system not really related to heart contractility

Question 25

Effect of hypercapnia on heart contractility

Answer 25

Leads to acidosis, which impairs cardiac function

Question 26

Valves closed during systole

Answer 26

Tricuspid, mitral (bicuspid) valves.

Question 27

Valves closed during diastole

Answer 27

Aortic valve

Question 28

Valves closed during isovolumetric contraction

Answer 28

Tricuspid, bicuspid, aortic valves

Question 29

Pressures and volumes of left heart during systole and siastole

Answer 29

Question 30

Way to tell hen a murmur is in the cardiac cycle

Answer 30

Feel carotid. When it pulses, that is systole.

Question 31

Answer 31

Question 32

Where on the LV pressure loop are stroke volume, ESV and EDV?

Answer 32

Question 33

How do we know that the heart has reserve maximum pressure?

Answer 33

Because the max pressure of the Starling curve is greater than that of the max pressure of the cardiac cycle loop

Question 34

Effects of increasing heart contractility

Answer 34

Decrease end systolic volume, increase stroke volume

Question 35

Effects of reducing compliance

Answer 35

Decreased stroke volume, decreased end diastolic volume

Question 36

Effects of increased aortic pressure

Answer 36

Decreased stroke volume, increased end systolic volume

Question 37

Afterload

Answer 37

Load encountered by ventricle as it begins contraction. Pressure applied by aortic hypertension, LV outflow tract obstruction

Question 38

Preload

Answer 38

The stretch on myocyte fibres before contraction A volume (EDV) load imposed by increased venous return