Blood Flow Regulation - Extrinsic Mechanisms

Question 1

Neural control facts

Answer 1

Most receive sympathetic but NOT PS innervation

Symp NT - norepineprhine

PS NT - Ach

Receptor for NE - alpha adrenergic

Question 2

Characteristics of symp control of BVs

Answer 2

Symp - more toward systemic needs

Under normal conditions - vasoconstrictors maintain the vasomotor tone

Most rapid to control pressure

Regulates contracticle states of both resistance and capicatance - increases venous pressure and venous return…venous actually more responsive

Question 3

Epi/NE - what, where, what do they do

Answer 3

Chief humoral factors affecting vasc resistance

From adrenal medulla in response to symp nerual activity

Act on alpha to produce constriction abd Beta-2 to produce vasodilation

Alpha greatly outnumbers the beta
…net effect is vasoconstriction and inc in vasc reistancer

Question 4

RAAS in geeneral

Answer 4

AT from liver
Renin from kidney
ACE from lung

Question 5

How does RAAS produce vasoconstriction

Answer 5

Direct
Potentiating symp act by inhibiting NE reuptake in postgang symp terminals
Elicit sec of endothelin from vasc endothelial cells
Symp activity releases renin which creates more AT2

Question 6

ADH functions and stimuli

Answer 6

From post pituitary

Low conc - Dec excretion of H2O

High conc - potent vasoconstriction

Sitmuli - osmotic conc of EC fluid and dec BV

Question 7

Hierarchy

Answer 7

Bottom tier - autogregulation…chiefly due to myogenic

Middle - Functional hyperaemia, endothelial secreiton, and autocoids

Top - extrinsic from outside by vasomotor nerves and hromones…under control from brain