Lecture 11- Cardiovascular homeostasis

Question 1

What are the major functions of the cv system?

Answer 1

• Transport of nutrients to the tissue
• Transport waste products away from tissue
• Transport/distribution of hormones

Question 2

Where does gas and nturient exchange occur?

Answer 2

In the systemic and pulmonary capillary beds

Question 3

Where is blood velocity slowest?

Answer 3

Capillaries

Question 4

Where is most blood found?

Answer 4

64% in the veins, reservoir

Question 5

What is the equation of blood flow?

Answer 5

Q = P/R

Question 6

What is poseuilles equation?

Answer 6

Q = P x pie x radiuis4 / 8nL

Question 7

What if pressure?

Answer 7

The force exerted on the vessel wall

Question 8

Describe where the largest pressure drop occurs

Answer 8

In the arteries/arterioles

Question 9

What is resistance?

Answer 9

Measure of pressure difference generated for a given flow rate

Question 10

What is conductance?

Answer 10

Measure of blood flow through a vessel for a given pressure difference

conductance = 1/R or pie r4/ 8nL

Question 11

Where is majority of resistance found in the vasculature?

Answer 11

In the muscular arteries, arterioles (84%)

Question 12

What else it is true about the vessels with the largest pressure drop?

Answer 12

They are under the most powerful vasomotor control

Question 13

Is blood flow controlled locally?

Answer 13

Yes local blood flow is intrinsically controlled;

• Each tissue needs to control its own blood flow proportional to its needs

Question 14

What are the tissue needs?

Answer 14

• Delivery of O2
• Delivery of nutrients, glucose, AA etc
• Removal of CO2, H and other metabolites
• Transport various hormones and other substrates to different tissues

Question 15

How is intrinsic control of blood flow achieved?

Answer 15

Autoregulation

Question 16

What is autoregulation?

Answer 16

The ability of tissue to maintain constant blood flow over a wide range of arterial pressures

Question 17

What are the theories for autoregulation?

Answer 17

Vasodilator Theory
Oxygen demand theory
Myogenic Theory

Question 18

What is the vasodilator theory?

1/3

Answer 18

• When there is an increase in tissue metabolism there is an increase in blood flow because local signals i.e CO2, H production cause the release of vasodilators, lowers arterial resistance and increased blood flow

Question 19

What is the oxygen demand theory?

2/3

Answer 19

Lowered tissue oxygen concentration leads to increased blood flow. This is because;

Low O2 delivery or Increased metabolism results in low tissue O2.

This leads to relaxation of arterioles and precapillary sphincters and increase blood flow to the tissue

Question 20

What is the myogenic mechanism?

3/3

Answer 20

Proposes that as arterial pressure falls the arterials have an intrinsic ability to dilate in response to decrease in wall tension

Tension = P x r

Question 21

Which of the three theories are correct?

Answer 21

It is likely that they are all integrated factors and that there are many other factors in reality.

Produces an autoregulation curve.

Question 22

What does autoregulation play a role in?

Answer 22

Active and reactive hyperemia.

Question 23

What is active hyperemia?

Answer 23

Increased blood flow in tissue i.e muscles during running to supply demand. This tails off/ back to norm post exercise

Question 24

What is reactive hyperemia?

Answer 24

Period of vascular occlusion is followed by a period of reactive hyperemia. i.e squatting a static exercise has no increase in blood flow and some occlusion, but there is lactic acid production, reactive hyperemia tries to restore this / the occlusion attempts to dilate to maintain blood flow.

Question 25

What are external factors regulating blood flow?

Answer 25

1) Humoral control

2) Neural factors

Question 26

What is humoral control of blood flow?

Answer 26

Adrenalin, adenosine, endothelin, NO

Question 27

What is neural control of blood flow?

Answer 27

Sympathetic vasomotor activity, tonically active supports blood pressue

Question 28

Describe some factors of local control of blood flow; *(summery)

Answer 28

• O2 demand
• Metabolic signals
• intrinsic myogenic
• Paracrine signals (ANG 2)

Question 29

Describe some external factors of blood flow; (summery)

Answer 29

• Endocrine signals
• Neural control
• Systemic blood volume and flow re-distribution
• Arterial pressure and cardiac function

Question 30

Whats the first step in CV system responding to exercise?

Answer 30

• Blood flow to active muscles can increase by up to 20x during exercise.
• increased systolic BP
• increased CO (HR and inotropy)

Question 31

What is the second step in cv system responding to exercise?

Answer 31

Redistribution of blood flow

• Skeletal muscle vasodilation autoregulation (O2, CO2, NO, K, adenosine (atp), pH)
• Sympathetic vasoconstriction of other muscles

Question 32

What is step 3 and 4 of CVS responding to exercise?

Answer 32

Redistribution of blood volume and increase in arterial blood pressure

• constriction of veins (mobilises venous pool into active circulation (inc VR = Inc CO)
• Constriction of almost all arterioles (inc TPR)
• Direct autonomic increase in HR and contractility (inc CO and inc BP)