Circulation: Local Control of Blood Flow Flashcards
what are the 2 types of blood flow control?
local
long term
what are 3 aspects of local control?
- tissue needs
- neural
- hormonal
what factor has the greatest impact on local control?
tissue needs
what are 2 aspects of long term control?
- kidney
- angiogenesis
what is angiogenesis?
change in number or size of blood vessels
(occurs with tumors -> highly vascularized)
what 3 things can stimulate the growth of new blood vessels?
- vascular endothelial growth factor (VEGF)
- fibroblast growth factor
- angiogenin
each of these cause increased vasculature of tumors
what is the vasodilator local control theory?
increased tissue metabolism causes release of vasodilators:
- increases vessel size
- decreases resistance and
- increases blood flow
what is the oxygen/nutrient lack local control theory?
increased tissue metabolism or decreased O2 causes:
- precapillary sphincter to relax
- more blood flow to capillary
- increases vessel size
- decreases resistance
- increases blood flow
both theories of local control of blood flow lead to…
increased vessel size + decreased resistance = increased blood flow
blood flow is proportional to ____
blood pressure
name the metabolic vasodilators
- adenosine
- AMP, ADP
- CO2 (lack of O2)
- H+ (lower pH)
- K+
- lactic acid
name the other vasodilators
- NO
- bradykinin
- substance P
- histamine
- leukotrienes
- lack of O2 (CO2)
name the vasoconstrictors
- serotonin
- NE
- epinephrine
- angiotensin II
- vasopressin (ADH)
- endothelin
(contain “in”)
what is active hyperemia?
increase in blood flow & BP brings more nutrients & O2 into tissue
what is reactive hyperemia?
increase in blood flow & BP brings increase in O2 to tissues, which causes rebound vasoconstriction back to normal size
active hyperemia and reactive hyperemia account for the theory of ____
autoregulation
what is the autoregulation theory?
if a vessel has either increased blood flow OR increased BP (=increased size), the blood vessel will react by decreasing in size (vasoconstriction), and vice versa
what percent of blood volume is in the systemic circulation?
84%
what percent of blood volume is in the systemic veins?
64% (*veins have the most volume)
what percent of blood volume is in the cardio-pulmonary system?
16%
which vessels have the largest compliance?
veins
what 3 factors determine venous return?
- skeletal muscle pump
- respiratory pump
- sympathetic NS
backflow in veins is prevented by ____
valves
problems with valves leads to ____
varicose veins
