Microcirculation, Coronary Circulation, Myocardial Oxygen consumption

Question 1

The Sterling Equation calculates the flow of which substance(s)?

Answer 1

Calculates the flow of water. It is dependent of the net forces influencing the movement of water.

Question 2

Blood flow through the capillaries is regulated by contraction and relaxation of ___ and ___.

Answer 2

Arterioles and precapillary sphincters.

Question 3

How do lipid-soluble substances cross the membranes of the capillary endothelial cells?

Answer 3

Simple diffusion.

Question 4

How do water, glucose, and amino acids cross the capillary?

Answer 4

Via the water-filled clefts between the endothelial cells.

Question 5

What does the Starling equation measure?

Answer 5

Measures fluid exchange across capillaries.

Question 6

What is the Starling equation?

Answer 6

J(v) = K (f) [ (Pc-Pi)-(πc - πi)]

Jv = Fluid movement
Kf = hydroaulic conductance (constant) 
Pc = capillary hydrostatic pressure 
Pi = interstitial hydrostatic pressure 
πc = capillary oncotic pressure
πi = interstitial oncotic pressure

Question 7

When Jv is positive, the net fluid movement is ____.

Answer 7

out of the capillary.

Question 8

Net fluid movement out of the capillary is defined as _____.

Answer 8

Filtration

Question 9

When Jv is negative, net fluid movement is ____.

Answer 9

into the capillary

Question 10

Net fluid movement into a capillary is defined as ____.

Answer 10

absorption

Question 11

An increase in Pc favors ____.

Answer 11

Filtration

Question 12

How does the Pc change if arterial or venous pressure is increased?

Answer 12

Pc is also increased.

Question 13

What is the normal value of Pi?

Answer 13

0 mm Hg (can be slightly negative)

Question 14

How does an increase in Pi affect filtration?

Answer 14

opposes filtration.

Question 15

How does an increase in πc affect filtration?

Answer 15

oppose filtration

Question 16

How does an increase in πi affect filtration?

Answer 16

favors filtration

Question 17

Factors that increase filtration:

1. ___Pc
2. ___Pi
3. ___πc
4. ___πi

Answer 17

1. Increased
2. Decreased
3. decreased
4. Increased

Question 18

You calculated the Starling equation and your answer is +6 mm Hg. Will filtration or absorption take place?

Answer 18

Filtration will occur.

Question 19

What are some examples of local (intrinsic) control of blood flow?

Answer 19

a. Autoregulation (by need) seen in heart, brain, and kidney
b. Active hyperemia - proportional to metabolic activity of that organ
c. Reactive hyperemia - occurs after a period of occulsion

Question 20

What is the myogenic hypothesis?

Answer 20

Mechanism explaining local control.

-Based on the idea that vascular smooth muscle contracts when it is stretched. This maintains a constant flow.

Question 21

What is the metabolic hypothesis of local control of blood flow?

Answer 21

• based on the idea that tissue supply of O2 is matched to tissue demand for O2.

Question 22

When metabolic activity in tissue is increased, what kind of metabolites are produced? Vasodilator or constrictor? Give examples

Answer 22

Vasodilator metabolites, like CO2, H+, K+, lactate, and adenosine.

Question 23

Give an example of a extrinsic control of blood flow.

Answer 23

Hormonal: sympathetic innervation, vasoactive hormoens like histamine, bradykinin, serotonin, and protaglandins.

Question 24

Histamine and bradykinin causes: __1__dilation and __2__ constriction, resulting in __3__ Pc and thus __4__ filtration. Net result __5__.

Answer 24

1. Arteriolar
2. Venous
3. Increased
4. increased
5. Local edema

Question 25

Coronary circulation is controlled mainly by____.

Answer 25

Local metabolic factors.

Question 26

What is the most important local vasodilator for the cerebral circulation?

Answer 26

Cerebral circulation is almost entirely controlled by local metabolic factors like Co2 which acts as a vasodilator to increase blood flow to the brain.

Question 27

Name two ways skeletal muscle blood flow is regulated.

Answer 27

1. sympathetic innervation - alpha receptors - vasoconstriction - during rest. beta 2 receptors- vasodilation during fight or flight response.
2. Local metabolic control. local vasodilator substances like lactate, adenosine, and K are produced after exercise .

Question 28

Blood flow to the skin: the principal function of the cutaneous sympathetic nerves is for __1___ regulation.

Answer 28

1. temperature