Frank Starling Mechanism

Question 1

Frank-starling mechanism

Answer 1

-the relationship between length and tension at the level of the cardiac muscle fiber and the left ventricle

Question 2

Sarcomere

Answer 2

• contractile unit of the cardiomyocyte
• when you increase stretch then force of contraction also increases

**there is an optimal length to produce maximal force (too much or too little stretch decrease force production)

Question 3

Operating point

Answer 3

-the point in which the length and force of contraction are at during cardiac muscle contraction

Question 4

Diastole

Answer 4

-filling of ventricle

Question 5

Left ventricle during diastole

Answer 5

-fills during diastole (preload)
-an increase in venous return will increase the preload (filling), which increases the stretch, and therefore the stroke volume

Question 6

Way to increase venous return

Answer 6

exercise

Question 7

Ways to decrease venous return

Answer 7

-hemorrhage

Question 8

Left ventricle end diastolic pressure (LVEDP)

Answer 8

-can be a surrogate for filling meaning it is the pressure/fill of the left ventricle during diastole (before systole)

Question 9

Afterloads effect on LVEDP

Answer 9

-afterload is the amount of pressure that the heart needs to exert to eject blood during ventricular contraction
-if increased, then a decrease in stroke volume will occur, and therefore an increase in LVEDP
-if decreased, then an increase in stroke volume, and decrease in LVEDP

Question 10

Inotropys effect on LVEDP

Answer 10

-Inotropy is the force/strength of muscular contractions
-if increased then an increase in stroke volume will occur, and therefore a decrease in LVEDP
-if decreased then a decrease in stroke volume will occur, and an increase in LVEDP

Question 11

Left ventricle pressure and volume

Answer 11

Phase A: diastole, LV filling
- increasing/high volume, low pressure
- mitral valve closes at end of this phase

Phase B: Systole, isovolumetric contraction
- High volume, increasing/high pressure
- aortic valve opens at end of this phase

Phase C: Systole, Ejection period
- low volume, high pressure
- aortic valve closes at end of this phase

Phase D: diastole, isovolumetric relaxation
- decreasing/low pressure, low volume
- mitral valve opens at end of this phase

Question 12

Stroke volume equation

Answer 12

End diastolic volume (EDV)-end systolic volume (ESV) = stroke volume

Question 13

Effects of increase preload

Answer 13

-increase preload (venous return/filling prior to contraction)
-results in increased end diastolic volume, increased stroke volume and increased contractility

Question 14

Effects of decreased preload

Answer 14

-decreased preload (venous return/filling prior to contraction)
-results in decreased end diastolic volume, stroke volume and contractility

Question 15

Effects of removed pericardium

Answer 15

-pericardium restricts ventricular filling (preload)
-when removed, dogs had better cardiac outputs during exercise because the ventricles are able to fill more

Question 16

Modulators of preload

Answer 16

-blood volume
-ventricular filling

Question 17

Modulators of blood volume

Answer 17

-RAAS
-blood loss
-fluid therapy

-muscle/respiratory pump
-venous compliance
-venous resistance
-right atrial pressure

Question 18

Modulators of ventricular filling

Answer 18

-tricuspid valve
-pulmonary valve/circulation
-pericardium (tamponade)

Question 19

Effects of increased afterload

Answer 19

-increased afterload (pressure LV must overcome to pump blood)
-results in increased end systolic volume (blood left after contraction), decreased stroke volume.

Question 20

Effects of decreased afterload

Answer 20

-decreased afterload (pressure LF must overcome to pump blood)
-results in decreased end systolic volume (ESV) and an increased stroke volume

Question 21

Modulators of afterload

Answer 21

-blood pressure
-ventricular ejection

Question 22

Ways that blood pressure is effected

Answer 22

CO X SVR
-affected by blood volume and sympathetic activity
- constriction/dilation of arteries (affected by sympathetic activation or deactivation, RAAS, local dilation vs hypertension)

Question 23

Ways that ventricular ejection is affected

Answer 23

-aortic or pulmonic valves

Question 24

Remodelling of heart and the next beat

Answer 24

-next beat will be higher or lower depending on the previous beat.
-an increase in afterload will result in an increased preload on the next beat = Self-correcting

Question 25

Effects of increased inotropy

Answer 25

• increased inotropy (contractility)
• results in decreased end systolic volume, and increased stroke volume

Question 26

Effects of decreased inotropy

Answer 26

-decreased inotropy (contractility)
-results in increased end systolic volume, and decreased stroke volume

Question 27

Modulators of inotropy

Answer 27

-state of arousal
-sympathetic activity (local norepinephrine, circulating factors epinephrine)
-parasympathetic activity (local acetylcholine)
-Calcium handling
-drug targets