(11) Contractility and Cardiac Output (Ballam)

Question 1

What are the 4 factors that you need to consider with cardiac output?

Answer 1

Heart rate

Contractility

Preload

Afterload

Question 2

What is contractility?

Answer 2

How foreceful the cardiac muscle contracts when stimulated

Question 3

What is positive iontropy?

Answer 3

Increased force of contraction

Question 4

What is negative iontropy?

Answer 4

Decreased force of contraction

Question 5

Contractility is generally proportional to…

Answer 5

Amount of calciu that is available to troponin on actin filaments

Question 6

Define Preload

Answer 6

Wall tension in RV or LV just before contraction is initiated

Question 7

Define Afterload

Answer 7

Pressure in ventricle that is required to eject blood

Question 8

Important concept with afterload:

Answer 8

Higher volume of blood to eject = lower velocity of ejection

Lower volume of blood to eject = higher velocity of ejection

Question 9

Identify where preload and afterload are on the graph

Answer 9

Question 10

What is the stroke volume equation?

Answer 10

Stroke volume (volume of blood ejected by ventricle with each beat)

SV = EDV -ESV

(usually about 70 mL)

Question 11

What is the ejection fraction equation?

Answer 11

Ejection fraction - fraction of the EDV ejected in each stroke volume

EF% = SV /EDV

(Usually about 55%)

Question 12

What is the equation for cardiac output?

Answer 12

CO (or Q) = SV x HR

*usually about 5L/min

Question 13

What is the frank-starling relationship?

Answer 13

Volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole

*relates length-tension to functionality

Question 14

Graphically, show what a positive vs. negative iontropic effect would look like

Answer 14

Question 15

Ventricular Pressure Volume Loops

Describe what is occuring in:

1 to 2

2 to 3

3 to 4

4 to 1

Answer 15

1 to 2 | Isovolumetric contraction

2 to 3 | Ventricular ejection

3 to 4 | Isovolumetric relaxation

4 to 1 | Ventricular filling

Question 16

Draw what increased:

Preload

Afterload

Contractility

Would look like in the Left Ventricle in comparison to normal

Answer 16

Question 17

Sympathetic stimulation causes a __________

Answer 17

Positive iontropic effect on CO

Question 18

Parasympathetic influence on CO includes ….

Answer 18

Negative ionotropic effect in atria only

Question 19

Increased heart rate (positive chronotropic effect) in turn…

Answer 19

Increases contractility (positive ionotropic effect)

Question 20

What is the positive staircase effect (bowditch staircase)?

Answer 20

More Ca2+ enters cells and taken up into SR

Question 21

What is postextrasystolic potentiation?

Answer 21

Arrhythmia, extra beat

Question 22

What does the Fick principle measure?

Answer 22

Cardiac output

Question 23

Draw the cardiac function curve

Answer 23

Question 24

The cardiac function curve represents __________ relationship

Answer 24

Frank starling

Question 25

What is occuring in Enhanced and Depressed cardiac function curve:

Inotropy

HR

Afterload

Answer 25

ENHANCED:

Inotropy: increased

HR: increased

Afterload: decreased

DEPRESSED:

Inotropy: decreased

HR: decreased

Afterload: increased

Question 26

If the overal resistance decreases… CO will

Answer 26

INCREASE