Cardiovascular Function (cardiac Output)

Question 1

What is the equation that calculates cardiac output?

Answer 1

CO= HR x stroke volume (SV)

Question 2

The Parasympathetic and sympathetic neurons connect to which node to regulate heart rate?

Answer 2

SA node

Question 3

Explain the pathway of how parasympathetic neurons decrease heart rate

Answer 3

Parasympathetic neurons (ACh)
>
Muscarinic receptors of autorhythmic cells
>
Increase K+ efflux; decrease Ca2+ influx
>
hyperpolarizes cell and decreases rate of depolarization
>
Decrease heart rate (-chronograph effect)

Question 4

Where is the cardiovascular control center?

Answer 4

Medulla oblongata

Question 5

Explain the pathway of how sympathetic neurons increase heart rate

Answer 5

Sympathetic neurons (NE)
>
beta1 receptors of autorhythmic cells
>
Increase Na+ and Ca2+ influx
>
Increase rate of depolarization
> 
Increase heart rate (+chronograph effect)

Question 6

What determines the stroke volume?

Answer 6

• force of contraction in ventricular myocardium
  
  • increase in contraction force=increase SV

SV=EDV-ESV

Question 7

What influences the force of contraction that determines the stroke volume?

Answer 7

-contractility

• end-diastolic volume (varies with venous return)
  
  • skeletal muscle pump
  • respiratory pump

Question 8

What is stroke volume (SV)?

Answer 8

-blood pumped per ventricle/contraction

Ventricular

Question 9

What is the equation to find stroke volume (SV) ?

Answer 9

SV= EDV (End diastolic vol) -ESV

Question 10

What determines the end diastolic volume (EDV)?

Answer 10

• depends on ‘venous return’ to heart chambers (right atrium)
  
  • changes sarcomeres length
  • changes contraction strength

Question 11

What is the length-tension relationship/ Frank- Starling Law?

Answer 11

An Increase in venous return, increase in ventricular wall stretch and increase in sarcomere length

Increase # of crossbridges and increase contraction force

-vice versa

Question 12

What is contractility (relating to SV)?

Answer 12

• cardiacs fibers intrinsic ability to contract

- dependent on ICF (Ca2+); ‘interaction with troponin, the # of crossbridges’

Question 13

What is the + inotropic effect of contractility?

Answer 13

-increase contraction force of heart

Question 14

Define Preload

Answer 14

-degree of cardiac muscle stretch (EDV) before contraction

Question 15

How is ejection fraction calculated?

Answer 15

SV/EDV x 100

Question 16

How is afterload calculated?

Answer 16

EDV + arterial resistance

Question 17

What is the function of digoxin (digitoxin)?

Answer 17

InActivates sodium potassium pump