Local Control Of Blood Flow

Front 1

1. What dictates the degree of local control of blood flow exhibited by a tissue?

Back 1

a. Its degree of metabolic activity
b. High metabolic activity=high control

Front 2

2. What do local control mechanisms determine?

Back 2

a. The distribution of cardiac output

Front 3

3. Where is the greatest drop in arterial blood pressure?

Back 3

a. Small arterioles

Front 4

4. What is myogenic tone in arterioles?

Back 4

a. Intrinsic level of tone that is independent of any neural or humoral influences

Front 5

5. What is resting tone in vascular beds?

Back 5

a. Tonic sympathetic vasoconstrictors establish overlying (to myogenic tone) tone that establishes the resting tone
b. Extrinsic influences can change tone above or below basal levels

Front 6

1. What determines vessel diameter?

Back 6

a. Transmural pressure
b. Pt=Pin-Pout

Front 7

7. If P out increases….

Back 7

a. Transmural pressure decreases, leading to vasoconstriction and increased resistance

Front 8

8. What does an increase in the activity of vasoconstrictor stimuli cause?

Back 8

a. Active vasoconstriction

Front 9

9. What does a decrease in active tone cause?

Back 9

a. Passive vasodilation

Front 10

10. What causes active vasodilation?

Back 10

a. Intrinsic or extrinsic influence results in a decrease in vascular resistance below basal tone

Front 11

11. What causes passive vasoconstriction?

Back 11

a. Dilatory influence is removed
b. Arteriolar tone returns to basal level

Front 12

12. What is vasomotion?

Back 12

a. The pattern of rhythmic changes in flow within a capillary bed
b. Some capillaries have high flow while others have low flow
c. There is a spontaneous and cyclical start-stop pattern to flow in capillaries due to random changes in precapillary resistance

Front 13

13. What is autoregulation?

Back 13

a. The intrinsic ability of an organ or tissue to alter local vascular resistance to maintain a constant blood flow despite changes in perfusion pressure

Front 14

14. What controls autoregulation?

Back 14

a. It is intrinsic
b. Can be demonstrated in the absence of any extrinsic influences

Front 15

15. What is the behavior of the vascular bed in the absence of autoregulation?

Back 15

a. Rigid tube
b. Flow changes in proportion to perfusion pressure

Front 16

16. What is the behavior of the vascular bed in the presence of autoregulation?

Back 16

a. Flow remains constant over a range of perfusion pressures

Front 17

1. What does autoregulation allow?

Back 17

a. Maintenance of tissue flow at low perfusion pressure
b. Protection of tissues against overperfusion and possible damage at high perfusion pressures

Front 18

18. What is vasoregulation?

Back 18

a. Much like autoregulation
b. Ability of the tissue to control blood flow to meet the metabolic needs while not over-perfusing the tissue

Front 19

19. What is myogenic vasoconstriction?

Back 19

a. Rapid stretch of vascular smooth muscle causes contraction
b. Resulting in a decrease in vessel lumen diameter that increases flow resistance

Front 20

20. What is the stimulus of myogenic vasoconstriction?

Back 20

a. Not necessarily stretch
b. There is a mechanism by which tension in the vessel wall is sensed
c. A decrease in radius in response to an increase in pressure will keep wall tension constant

Front 21

21. What is the purpose of the myogenic response?

Back 21

a. Protection of capillaries from sudden increases in blood pressure
b. May also play role in vasodilation associated with contraction of skeletal muscle

Front 22

1. What is the purpose of metabolic vasodilation?

Back 22

a. Increase tissue blood flow and delivery of oxygen and substrates
b. Removal of metabolic waste products
c. All in proportion to tissue metabolism

Front 23

23. What are autocoids?

Back 23

a. Locally produced vasoactive substances
b. Generally vasodilators
c. No one substance leads to systemic vasodilation

Front 24

24. When arterial pressure decreases and tissue flow and oxygen delivery fall….

Back 24

a. Metabolic factors predominate
b. Leads to vasodilation

Front 25

25. When do myogenic factors predominate?

Back 25

a. When arterial pressure increases
b. Increase in blood flow

Front 26

26. What is endogenic vasoregulation?

Back 26

a. Endothelium in small resistance vessel produce NO in response to shear stress
b. Gap junctions exist between endothelial cells and vascular smooth muscle cells, allowing for communication

Front 27

27. How are intrinsic neurons involved in control of blood flow?

Back 27

a. Transmission of excitation and/or inhibition long vessel segments
b. Gap junctions may help facilitate segmental conduction along vessels

Front 28

28. What is tissue pressure theory?

Back 28

a. NOT true autoregulation
b. High perfusion to encapsulated organs can lead to excessive fluid filtration and edema
c. Leads to increased tissue pressure
d. Increase in pressure can compress blood vessels and reduce blood flow
e. Decompression leads to increased flow

Front 29

29. What is reactive hyperemia?

Back 29

a. Flow to a tissue is restored after a period of ischemia
b. Restored flow exceeds pre-ischemic levels

Front 30

30. What determines the magnitude and duration of reactive hyperemia?

Back 30

a. Duration of ischemic period
b. Accumulation of metabolic byproducts

Front 31

31. What is active hyperemia?

Back 31

a. During periods of increased tissue metabolic activity, the rate of substrate utilization and metabolic waste production increases dramatically
b. With increased metabolic activity is an increase in blood flow

Front 32

32. What causes active hyperemia?

Back 32

a. Accumulation of vasodilator substances

Front 33

33. When does blood flow in the muscle pump?

Back 33

a. Relaxation

Front 34

34. How does temperature affect blood flow?

Back 34

a. Increase=vasodilation
b. Decrease=vasoconstriction

Front 35

35. What is the action of directly acting vasoactive substances?

Back 35

a. Local only
b. Not involved in the systemic regulation of blood pressure

Front 36

36. What are endothelins?

Back 36

a. 21 AA peptides
b. Most potent vasoconstrictor substance yet identified

Front 37

37. How does diabetes affect blood flow?

Back 37

a. Reduced capillary perfusion
b. Decreased production of NO and increased scavenging of NO
c. Poor control of flow at tissue level
d. Lack of response to extrinsic mehanisms

Front 38

38. How does anaphylactic shock affect blood flow?

Back 38

a. Vasodilation
b. Increased vascular permeability
c. Peripheral vascular pooling