Control of Cardiac Output/Cardiac Cycle

Question 1

7 phases of cardiac cyce

Answer 1

(Systole 2,3,4)(Diastole 5,6,7,1)
2- Isovolumetric contraction
3- Rapid ejection
4- Reduced ejection
5- Isovolumetric relaxation
6- Rapid filling
7- Diastasis
1- Atrial systole

Question 2

Phase 1

Answer 2

Atrial systole
NOT REQUIRED
20-40% of LV filling
LVEDV=120ml
Possible s4

Question 3

When are all valves closed?

Answer 3

Phase 2- isovolumetric contraction
S1= mitral valve closes
ALSO
Phase 5- isovolumetric relaxation
S2= pulmonic and aortic valves close

Question 4

When are pulmonic and aortic valves open?

Answer 4

Phase 3- rapid ejection
No heart sounds

Question 5

What percent ejects during phase 3?

Answer 5

70%

Question 6

LVESV

Answer 6

50ml

Question 7

Phase 6

Answer 7

Rapid ventricular filling
Possible S3

Question 8

Phase 7

Answer 8

Reduced ventricular filling
Diastasis

Question 9

Frank sterling law

Answer 9

The bigger the preload, the bigger the force of contraction and thus bigger SV (within limits)
When the sarcomere length is increased, more actin and myosin can bind, causing bigger contraction
Cardiac SV responds more to preload than nuerohormonal mechanisms like the intrincsic heart nodes
Matching venous return to cardiac output in BOTH ventricles
Changes force in contraction and SV in response to venous return
Increase volume increases contraction

Question 10

What is the more independent flow?

Answer 10

Arterial is less controlled by blood flow and CO

Question 11

What is CO? Not the equation

Answer 11

Quantity of blood pumped into the aorta each minute

Question 12

Venous return

Answer 12

The amount of blood coming into the RA each minute

Question 13

What controls CO normally?

Answer 13

Venous return, the heart is not the primary controller of CO

Question 14

SV formula

Answer 14

EDV- ESV

Question 15

EF

Answer 15

SV/EDV

Question 16

What controls heart pumping?

Answer 16

ANS
SNS can double CO
ANS can decrease CO to almost 0 by vagal

Question 17

What is more important for changing CO? HR or SV

Answer 17

HR

Question 18

Bowditch (Treppe) Effect

Answer 18

“staitway effect”
Increase in Hr also increases inotropy
Due to an increase in intracellular CA with higher HR
NaK-ATPase cant keep up with influx of Na, so Na/Ca pump doesnt work well

Question 19

Values for SV, EDV, ESV

Answer 19

70ml
120ml
50ml (wont close all the way like alveoli wont), but can decrease to 20 under high inotropy effect, EDV increases, which bumps sv to 150ml

Question 20

Preload and how its measured

Answer 20

Tension of cardiac myoctyes
Related to sarcomere length
LVEDV
LVEDP
PCWP
CVP

Question 21

Frank starling curve

Answer 21

Looks like small s curve with the same starting point but different end points
Shift right and down- means increased afterload or decreased inotropy
Shift left and up, means increased inotropy or decreased afterload

Question 22

Laplace law

Answer 22

T(Wall stress)= P(pressure) R(Radius) /H(thickness

Question 23

What is responsible for the increased CO that follows an increase in afterload? (Primary and delayed)

Answer 23

1. Frank sterling mechanism/Troponin C sensitivity to calcium
2. CA increase by SR

Question 23

What increases afterload?

Answer 23

Aortic pressure
SVR
AV Stenosis
Ventricular dilation

Question 23

What does increased afterload do to LVESV and SV?

Answer 23

Increases LVESV, decreases SV

Question 24

What can and cant change heart force?

Answer 24

Can:preload- dependent activation, inotropy-independent activation
Cant: recruitment like other skeletal muscles

Question 25

When does CA influx to increase inotropy, what phase?

Answer 25

Phase 2

Question 26

What (physiologic) 3 ways to stimulate inotropywith calcium

Answer 26

CA influx phase 2 during AP
Increasing CA by SR
Sensitizing Trop-C to CA

Question 27

What does SNS effect mostly in the heart?

Answer 27

Inotropy, ventricular and atrial inotropy

Question 28

What does PNS affect mostly in the heart?

Answer 28

Negative effect on atria, minimal on ventricles

Question 29

Anrep affect

Answer 29

Sudden increase in afterload will increase inotropy
Increasein afterload increases LVEDP, frank starling causes increased inotropy
Only lasts for 15 minutes
Primary- frank starling, trop c sensitize
delayed- SR release of CA