Local Blood Flow Regulation

Question 1

dense bodies

Answer 1

structures that actin filaments attach to in smooth muscle cells in the interior of the cell

correlates to the Z-line

Question 2

dense bands

Answer 2

structures where actin filaments attach to the inner surface of the cell

Question 3

latched state

Answer 3

the state of contraction in smooth muscle that can be maintained by low energy consumption

probably involves very slow cycling or even non-recycling cross-bridges

Question 4

regulation of smooth muscle contractile activity

Answer 4

changes in intracellular free calcium levels

changes in calcium sensitivity of the contractile machinery

Question 5

calcium release from the SR in smooth muscle

Answer 5

voltage operated calcium channels

receptor operated calcium channels

chemical activation (IP3) of calcium release calcium binds with calmodulin to activate myosin light chian kinase, promoting contraction

Question 6

mechanisms for smooth muscle contraction

Answer 6

protein kinase C linked receptors

coupled via a G protein to phospholipase C

IP3 causes calcium release from SR

DAG activates PKC

Question 7

mechanisms for smooth muscle relaxation

Answer 7

calcium is pumped back into the SR

nitric oxide generated cGMP inhibits myosin kinase and promotes relaxation

Question 8

factors regulating vascular smooth muscle contraction

Answer 8

activity of symathetic nerves

agents produced and/or secreted by the endothelium

factors in circulation such as hormones, catecholamines, blood gases

Question 9

renin-angiotensin system

Answer 9

angiotensin -> angiotensin I (through renin) -> angiotensin II (through ACE)

angiotensin II receptors are of the AT₁ subtype

leads to vasoconstriction and aldosterone release

Question 10

autoregulation

Answer 10

process by which a change in the perfusion pressure is countered by a change in resistance in the vascular bed that kepes flow relatively constant

Question 11

theories for mechanisms of autoregulation

Answer 11

myogenic

metabolic

tissue pressure

Question 12

myogenic mechanism of autoregulation

Answer 12

the vascular smooth muscle contracts in response to stretch and relaxes with a reduction in the stress

Question 13

metabolic mechanisms of autoregulation

Answer 13

blood flow is linked to the metabolic activity of the tissue

a change in the oxygen supply will produce a change in the amount of a “metabolite” that is vasoactive

Question 14

tissue pressure mechanism of autoregulation

Answer 14

a change in perfusion will produce a change in the interstitial pressure, which will change the external force on the blood vessels in the tissue

most operable in tightly encapsulated tissue (limited compliance)

Question 15

hyperemia

Answer 15

imbalance between oxygen supply and demand that leads to a relative increase in blood flow

functional - due to increased metabolism

reactive - due to metabolic debt

Question 16

endothelial factors

Answer 16

nitric oxide

prostacyclin

endothelin 1

endothelial dependent hyperpolarizing factor (EDHF)

Question 17

prostacyclin

Answer 17

an arachidonic acid metabolite with actions similar to NO

released from endothelial cells in response to many stimuli including hypoxia, shear stress, acetylcholine, and platelet products such as serotonin

causes relaxation of vascular smooth muscle through cAMP mechanisms

Question 18

endothelial dependent hyperpolarizing factor (EDHF)

Answer 18

also acts like nitric oxide

hyperpolarizes adjacent vascular smooth muscle cells and causes relaxation

Question 19

endothelin 1

Answer 19

potent vasoconstrictor

produced by endothelial cells in response to stimuli

under normal circumstance, vasodilator influences predominate

Question 20

nitric oxide synthesis

Answer 20

Question 21

interaction of endothelium with platelets

Answer 21

in the absence of vascular injury, the vasodilators regulate platelet interaction and vessel dilation

in the case of injury, vasodilators are downregulated, and this promotes vessel contraction as well as allows platelet aggregation

Question 22

promoters of vascular growth

Answer 22

vascular endothelial growth factor (VEGF) - tyrosine kianse receptor

fibroblast growth factors (FGFs) - embryonic, fetal, and postnatal development

angiopoietin-1 (ANGPT1) - endothelial cells, required for embryonic vascular development

Question 23

inhibitors of vascular growth

Answer 23

EC matrix of tumros and breakdown product of collagen XVII to make endostatin

angiostatin from plasminogen - enhanced apoptosis of endothelial cells

angiopoietin-2 (ANGPT2) - antagonist of ANGPT1

Question 24

epinephrine

Answer 24

potent vasoconstrictor and cardiac stimulant

beta1 - chronotropic for heart

beta2 - dilates muscle vessels

alpha receptors lead to vasoconstriction in the veins and vasodilation in the arterioles due to the beta2 effect

Question 25

norepinephrine

Answer 25

similar effect as epinephrine on beta1

relatively little beta2 effect

increases peripheral resistance and both diastolic and systolic BP

alpha receptors lead to vasoconstriction on both the venous and arterial sides

leads to vagal reflex, so HR is not increased

Question 26

isoproterenol

Answer 26

potent agonist of both beta1 and 2

minimal to no effects on alpha receptors

Question 27

parasympathetic innervation of the heart

Answer 27

Ach binds muscarinic receptors in nodes and muscle, leads to slowing of heart and AV conduction

only small changes in contractility

Question 28

basal arterial tone

Answer 28

theoeretical reference point

amount of vascular contractions during resting conditions

assumed that no neural factors are present

Question 29

resting sympathetic tone

Answer 29

amount of vascular contraction found under resting conditions as a result of tonic sympathetic nerve activity

resistance is higher than the basal arterial tone due to presence of a tonically released vasoconstrictor, NE

Question 30

overall effect of circulating epinephrine

Answer 30

moderate increase in arterial blood pressure (due to increased cardiac output

Question 31

overall effect of circulating norepinephrine

Answer 31

higher affinity for alpha receptors

greater increase in arterial blood pressure than epinephrine