Physiology Test 2 Flashcards
Humoral Control of Circulation
(Vasodilators)
Bradykinin
Histamine
Atrial naturetic peptide
Serotonin
Prostaglandins
Humoral Control of Circulation
(Vasoconstrictors)
NE (and Epi)
Angiotensin II
ADH
Control by Ions & Other Factors (Vasodilators)
K+
Mg++
H+
Acetate & citrate (mild)
CO2 (esp. in brain)
Control by Ions & Other Factors (Vasoconstrictors)
Ca++
Long term regulation
is more effective than short term
Long term changes
are due to changes in vascularization
Angiogenesis
formation of new vessels. In response to O2 demand (maximal, not average)
Requires vascular growth factors
vascular growth factors
VEGF – vascular endothelial growth factor
FGF – fibroblast grown factor
PDGF – platelet-derived growth factor
Angiogenin
VEGF
vascular endothelial growth factor
FGF
fibroblast grown factor
PDGF
platelet-derived growth factor
Inhibition of vascularization
Angiostatin
Endostatin
Vasoconstrictors (Endothelin)
Released in response to vessel injury
Prevents blood loss
Vasodilators
NO
Released from endothelial cells in response to shear stress (important in larger vessels)
Half life of ~6 sec
Activates guanylate cyclase, which converts GTP to cGMP, which activates PKG, causing relaxation
Kidneys
Tubuloglomerular Feedback (in Urinary)
Brain
Also regulated by CO2/H+
Skin
Tied to body temperature regulation
Myogenic Theory
Sudden stretch of small vessels leads to contraction
Theory: Stretch of smooth muscles opens mechanically-gated Ca++ channels
Increase in Ca++ in vascular smooth muscle leads to increased contraction
Reactive Hyperemia
Increase in flow in response to blocked flow
Active Hyperemia
Increase in flow in response to increased metabolism
O2 Demand Theory
O2 decrease in tissues leads to relaxation of smooth muscle
Because O2 is needed for contraction
Relaxation reduces resistance
Flow increases
Vasodilator Theory
Metabolism produces vasodilator substances
Adenosine
Adenosine phosphate compounds
Histamine
CO2
K+
H+
Substances reduce resistance
Flow increases
Physics of Flow
Flow through a vessel is determined by
pressure difference between ends of vessel
Delta P or P1 - P2
Resistance of vessel
Flow (Q) = Delta P/R
Increases in metabolism
increase flow