Lecture 1: CV function

Question 1

What is the frank starling mechanism?

Answer 1

Increased venous return and cardiac stretching results in increased systolic force. This is up to a point where it plateaus.

Question 2

What is venous return to the heart limited by?

Answer 2

Mean right atrial pressure. As this increases venous return diminishes to zero.

Question 3

What determines the venous return plateau?

Answer 3

Pleteau exists as large veins are partially collapsed due to insufficient pressure thus limiting venous return until venous pressure is increased.

Question 4

Whats the relation of venous return and frank starling mechanism?

Answer 4

Venous return is equal to cardiac output.

Exercise of blood transfusions shift the venous return curve because it alters venous filling pressure and increases cardiac output.

Question 5

What factors change cardiac output?

Answer 5

• Inotrope
• HR (SV and inotropy)
• Afterload
• Preload

Question 6

What is organ blood flow proportional to?

Answer 6

• Organ mass
• Metabolic rate

Question 7

What are the extrinsic controls of the CV system?

Answer 7

Neural
- SNS, PSNS

Endocrine
- Catecholamines
- RAAS
- ADH
- Natriuretic peptides

Question 8

Describe the baroreflex:

Answer 8

AA and CB baroreceptors relay to the medullary CV center

-> SNS to heart increase HR and Intropy (decrease vagal to heart)
-> Increased SNS to kidney = Renin
-> Vasoconstriction of resistant vessels

Question 9

Describe RAAS:

Answer 9

Decrease in renal perfusion (JGA) -> Increased Renin.

Renin converts Ang-> ANG1, ACE converts ANG1->ANG2

ANG2
-> ANP secretion inc.
-> ADH secretion inc.
-> Vasoconstriction of vessels
-> Aldosterone inc.
-> Inc. Na,Cl reabsorption, inc. K secretion
-> Inc. SNS activity
-> Inc. GF pressure

Question 10

Describe how ANP and BNP work?

Answer 10

Cardiac distension
-> ANP or BNP
=
-> Decrease renin
-> Vasodilation
-> Increased GFR = Natriuresis, diuresis