Lecture 12 Regulation of CO

Question 1

What happens with the baroreceptor reflex and autonomic nervous system when someone gets a fluid/infusion?

Answer 1

Bec/ inc RA pressure–> increased CO–> inc ARTERIAL pressure –> inc Baroreceptor reflex (increased activity/firing/stretching) –> dec HR

Question 2

What are the 3 major factors that control heart rate?

Answer 2

1. ANS and baroreceptors dec HR
2. Bainbridge reflex increases HR
3. Chemoreceptors detecting changes in mainly CO2 (also pO2 and pH)

Question 3

What is the body’s response when peripheral chemoreceptors detect higher CO2?

Answer 3

If CO2 rises, oxygen has gone down so chemoreceptors will sense this and cause HR to lower = BRADYCARDIA (bec/ blood is not adequately oxygenated so don’t want to be pumping it all around the body) and INCREASE IN BREATHING RATE which then inhibits slow heart rate

Question 4

To control/regulate CO, you must regulate ________?

Answer 4

Stroke volume

Question 5

What are inotropic effects?

Answer 5

affecting strength of cardiac muscle (Inotropic state = Contractility)

Question 6

What is preload?

Answer 6

degree of filling of heart before contraction (really, it’s a measure of the amount of stretch of cardiac muscle)

To vary preload, you can change venous reservoir which changes venous pressure and ventricular filling

Question 7

Higher preload does what to stroke volume and force of contraction?

Answer 7

Higher stroke volume and higher/greater FORCE of CONTRACTILITY but NOT a change in contractility

Question 8

What is inotropic state?

Answer 8

contractility

Question 9

Force of muscle contraction (power exerted during a contraction) is a function of what factors?

Answer 9

preload, afterload, underlying contractility of muscle

Question 10

During systole, what is preload and afterload actually?

Answer 10

Preload = depends on End Diastolic Volume
Afterload = arterial and ventricular pressure during systole

Question 11

What is contractility?

Answer 11

intrinsic ability for the myocardium/heart muscle to contract

Question 12

Does higher end diastolic volume correspond to higher systolic pressure?

Answer 12

Yes (bec/ higher EDV = higher systolic pressure)

Question 13

What is the driving force (gradient) for blood flow in the system?

Answer 13

difference between EDP and systolic pressure

Question 14

Which ANS system predominates for HR at rest?

Answer 14

PSN predominates AT REST for HR!!

Question 15

What is the MAIN THING CONTROLLING YOUR HEART RATE DURING NORMAL FUNCTION?

Answer 15

PSN = ARTERIAL BARORECEPTOR REFLEX (can only sense high pressure so reduced activity if there’s low pressure)

Question 16

What does the Bainbridge reflex do to HR?

Answer 16

Low pressure receptors in Atria that increase HR

Bainbridge reflex = venous (not arterial) = increases sympathetic activity to increase HR

Question 17

Peripheral chemoreceptors detect changes in what 3 things?

Answer 17

pCO2, pO2 and pH

Question 18

What are the 6 factors that control HR?

Answer 18

1. ANS and baroreceptors dec HR
   
   2. Bainbridge reflex increases HR
   3. Chemoreceptors detecting changes in CO2
   4. Respiratory effects (breathing)
   5. Hormonal affects
      
      6. Temp