Physiology 3 - Cardiovascular Physiology

Question 1

What is the Main Function of the Heart?

Answer 1

To generate pressure to overcome resistance to drive flow

Question 2

What is Cardiac Output?

Answer 2

• HR x SV
• “the performance of the heart”

Question 3

How does the heart generate pressure?

Answer 3

• Electrical
  
  • Electrical activation: heart rate
  • SA node - stimulates atria to contract
  • AV node - pause for atrial filling
  • Purkinje fibers - ventricular contraction
• Mechanical
  
  • Muscular activation: stroke volume
  • Cardiac Myocytes
  • Systole
  • Diastole

Question 4

What is Stroke Volume?

Answer 4

EDV-ESV

Question 5

What are the events of Electrical Activation of the Heart?

Answer 5

1. SA node depolarizes
2. Action potential spreads throughout atria
3. Action potential goes through AV node and into Purkinje fibers of bundle of His
4. This deploarizes the septums and then the rest of the ventricle from apex to base via P fibers and gap junctions

Question 6

What are the Mechanical Phases of the Cardiac Cycle?

Answer 6

Question 7

What Ion is Responsible for Resting Membrane Potential?

Answer 7

Potassium

Question 8

What Ion is responsible for depolarization of muscle cells?

Answer 8

Sodium

Question 9

What Ion is responsible for deploarization of SA/AV nodes?

Answer 9

Calcium

Question 10

What Ions are responsible for repolarization?

Answer 10

Potassium moving out of cell

Question 11

What is the Shape of an Action Potential Seen in SA or AV node?

Answer 11

Question 12

What is the Shape of an Action Potential Seen in Cardiac Muscle Cells?

Answer 12

Question 13

What is the Extrinsic Control of the Heart?

Answer 13

ANS Regulation: SNS (beta 1 receptors) vs. PNS (muscarinic receptors)

Question 14

What are the Effects of Sympathetic Stimulation on the heart?

Answer 14

• Increase in heart rate
  
  • decrease in duration of diastole (mainly)
  • decrease in duration of systole
• Increase in contractility
  
  • increase in force of contraction
  • increase in speed of contraction
  • greater volume ejected in shorter time
• Both HR and SV increase, increasing CO

Question 15

What are the Effects of Parasympathetic Stimulation on the Heart?

Answer 15

• Decrease in heart rate
  
  • Increase in duration of diastole (mainly)
  • Increase in duration of systole
• Modest decrease in contractility
  
  • decrease in force of contraction
  • decrease in speed of contraction
  • slightly lesser volume ejected in longer time
• Both HR and SV decrease, decreasing CO

Question 16

What is Preload?

Answer 16

Volume that comes back to the heart

Question 17

What is Afterload?

Answer 17

Amount you have to contract against in order to push blood out of heart

Question 18

What is the Effect of Preload on Stroke Volume?

Answer 18

• Usually, but not always, an increase in EDV (or preload) increases the calcium entry into the ventricles, which increases the force of contraction
• This results in an increase in the stroke volume
  *

Question 19

What is the Starling Mechanism?

Answer 19

The tendency of the heart to alter contractile force to keep the ESV approximately constant

Question 20

What is Starling’s Law of the Heart?

Answer 20

The principle that the heart varies its SV with changes in EDV so as to reach a roughly constant ESV

Question 21

What determines Blood Pressure? (The equations)

Answer 21

Question 22

What two things contribute to Mean Arterial Blood Pressure?

Answer 22

Cardiac Output (Q) and TPR

Question 23

How do you obtain the MAP from a Blood Pressure reading?

Answer 23