Cardiovascular Part 3

Question 1

Stroke Volume

Answer 1

Volume of blood ejected per cardiac cycle.

Difference between end diastolic
volume (EDV) and end systolic volume (ESV)

SV = EDV - ESV

SV = 135 – 65 = 70 ml

Question 2

SV influenced by

Answer 2

1. Preload = EDV
2. Sympathetic nervous system
3. Afterload: Ventricular force required to open the semilunar valves during systole

Question 3

CO

Answer 3

HR x SV

Question 4

Frank-Starling Mechanism

Answer 4

Ability of the heart to change its force of contraction and therefore stroke
volume in response to changes in venous return (myocardial stretch)

Venous return affects EDV
– ↑ venous return = ↑ EDV
– ↑ EDV = ↑ ventricular
myocardial fiber stretch
– Slow heart rate = ↑ EDV
– Exercise = ↑ EDV

↑ EDV = ↑ ventricular myocardial fiber stretch = ↑ x-bridges = ↑ force = ↑ SV (optimal alignment of the actin and myosin)

Question 5

Three things contribute to the resistance:

Answer 5

1. Blood viscosity
   * Volume
   * # of RBC
2. Total blood vessel length
   * how much tubing is needed
   * body mass
3. Blood vessel diameter
   * relaxed vessels decrease resistance
   * constricted vessels increase resistance
   * biggest contributor to minute-to-minute control of
   resistance 22

Question 6

pulmonary arteries

Answer 6

carry deoxygenated blood to
the lungs to get oxygenated

Question 7

Plasma

Answer 7

carries blood cells, proteins, nutrients, metabolic wastes, and other molecules being transported around the body

Question 8

Blood

Answer 8

• Cells
• Cell fragments
• Plasma (mostly water)

Question 9

Ejection Fraction

Answer 9

EF = SV / EDV

The ejection fraction (EF) formula equals the amount of blood pumped out of the ventricle with each contraction (stroke volume or SV) divided by the end-diastolic volume (EDV), the total amount of blood in the ventricle.

Question 10

How do the SNS and PSNS affect the heart rate?

Answer 10

SA Node alone = 100 BPM
* Modulated by ANS
* Normal = 70-75 BPM

• SNS: ↑HR
• Opens more Na+ channels
• Reduces time to threshold
• Shorter time between beats =
  ↑HR
• PSNS: ↓HR
• Opens more K+ channels
• Increases time to threshold
• Longer time between beats = ↓HR

Question 11

Length-tension relationship

Answer 11

Optimal length = maximal force
– More x-bridges
– Tightening of filaments
– ↑ Ca2+ from SR

Too long or too short = inefficient pumping

Question 12

Sympathetic Effects on Cardiac Muscle

Answer 12

1. E/NE bind to receptor
2. Activates G-protein coupled receptor
3. Activates adenylyl cyclase
4. ATP = cAMP
5. Activates kinase
6. Activates:
7. L-type Ca2+ channels
8. RyR on SR
9. Troponin on actin
10. X-bridges on myosin
11. Ca2+ pumps in SR
12. Increases contraction
    strength= ↑ SV

Question 13

Afterload

Answer 13

Ventricular force required to open the semilunar valves during
systole

(Hypertension can increase)

Question 14

Blood consists of

Answer 14

• Cells
• Cell fragments
• Plasma (mostly water)

Question 15

Exceptions

Answer 15

Pulmonary arteries carry deoxygenated blood to
the lungs to get oxygenated

Pulmonary veins carry oxygenated blood to the heart to get sent to the rest of the body

Question 16

Three things contribute to the resistance:

Answer 16

1. Blood viscosity
   * Volume
   * # of RBC
2. Total blood vessel length
   * how much tubing is needed
   * body mass
3. Blood vessel diameter
   * relaxed vessels decrease resistance
   * constricted vessels increase resistance
   * biggest contributor to minute-to-minute control of
   resistance 22