Control of Tissue Blood Flow

Question 1

What organs have alpha-1 receptors?

Answer 1

GI, skin

Question 2

What organs have beta-2 receptors?

Answer 2

skeletal & coronary arteries

Question 3

What kind of receptors do cerebral arteries have?

Answer 3

THEY DO NOT RESPOND TO NEURAL/ENDOCRINE CONTROL. only local.

Question 4

What contribution does the PNS make to neural control of tissue blood flow?

Answer 4

Vasodilation & secretion of the salivary gland through VIP & ACh

Question 5

What compounds have effects as hormones to control tissue blood flow?

Answer 5

1) epinephrine
2) AngII
3) ADH/Vasopressin
4) Bradykinin
5) Histamine

Question 6

How does AngII affect tissue blood flow?

Answer 6

directly causes smooth muscle vasoconstriction

–> increase TPR

Question 7

How does ADH affect tissue blood flow?

Answer 7

causes vasoconstriction & water/salt retention

Question 8

How does bradykinin affect tissue blood flow?

Answer 8

causes vasodilation & increased capillary permeability

Question 9

How does histamine affect tissue blood flow?

Answer 9

vasodilation & increased capillary permeability

Question 10

What cells release histamine?

Answer 10

mast cells & basophils

Question 11

where are mast cell located?

Answer 11

tissue

Question 12

where are basophils located?

Answer 12

blood

Question 13

How bradykinin activated?

Answer 13

1) lysis/inflammation –> kallikrein activation
2) kallikrein: a2-globulin –>kallidin
3) kallidin –> bradykinin

Question 14

How is bradykinin inactivated?

Answer 14

carboxypeptidase or ACE

Question 15

What are the two theories for local control of tissue blood flow?

Answer 15

1) vasodilator

2) nutrient/o2-lacking theory

Question 16

Describe the vasodilator theory of local control?

Answer 16

increased metabolism –> vasodilator production

vasodilators: adenosine, histamine, H+, CO2

Question 17

Describe the nutrient/O2 lacking theory.

Answer 17

1) Decreased flow –> O2/nutrient depletion

2) inability of vessels to contract, so they relax

Question 18

Define autoregulation.

Answer 18

acute increase in P will increase Q, but Q returns to normal within a range of P’s

Question 19

What are the 2 theories for autoregulation?

Answer 19

Metabolic & Myogenic

Question 20

Describe the myogenic theory for autoregulation.

Answer 20

Vascular smooth muscle contracts due to stress-activated channels

Question 21

Describe the metabolic theory for autoregulation.

Answer 21

Increased o2 + nutrients –> contraction

Question 22

When is endothelin released?

Answer 22

endothelium releases endothelIN due to damage to prevent blood loss

Question 23

What are the consequences of endothelin in HTN?

Answer 23

may cause additional vasoconstriction

Question 24

How are endothelin receptors used in drug therapy?

Answer 24

endothelin receptor antagonists for pulmonary HTN

Question 25

What is the primary form of regulation for cerebral arteries?

Answer 25

local control

Question 26

How does local regulation play into the overall regulation in cardiac & skeletal muscle?

Answer 26

local can override SNS in cardiac/skeletal muscle.

Question 27

What are other effects of EDRF / NO?

Answer 27

1) inhibition of leukocyte adhesion (infection) 2) inhibition of platelet adhesion (thrombus) 3) inhibition of vascular smooth muscle proliferation (atherosclerosis)

Question 28

How is eNOS activated?

Answer 28

shear stress activation of clarithrin receptor

Question 29

What reaction does eNOS catalyze?

Answer 29

O2 + L-arginine --> NO + L-citrulline

Question 30

How does NO promote vascular relaxation?

Answer 30

1) NO diffuses to smooth muscle, activates soluble guanylate cyclase 2) SGC: GTP --> cGMP to activate PKG cGMP promotes relaxation

Question 31

How is cGMP inactivated?

Answer 31

Phosphodiesterases

Question 32

How is Viagra used to promote vascular relaxation?

Answer 32

prevents PDE-5 from inactivating cGMP

Question 33

How is the need for neovascularization determined?

Answer 33

determined by MAX (not average) required blood flow to overcome a given hypoxia

Question 34

How do tumor cells promote vascularization?

Answer 34

1) tumor cells release signal to cause change in cell type 2) perivascular cells detach & remodel 3) angiogenic/inflammatory stimuli attract other cells - - platelets, endothelial progenitor cells, myeloid cells

Question 35

Why does angiogenesis continue in a neoplasia?

Answer 35

Tumor angiogenesis does not improve hypoxic environment. Vessels are leaky & tumor is poorly perfused