Lecture 16: Local Control of Blood FLow Flashcards
what 3 things regulate arteriolar diameter
local, auto-regulatory control
autonomic fiber release of nitric oxide
sympathetic NS (like Epi)
what is metabolic theory (active hyperemia)
local metabolic factors can increase blood flow to active muscles
tissue supply of oxygen matches the tissue demand for oxygen
what is myogenic response (flow autoregulation)
arteriolar smooth muscle responds to changes in arteriolar blood pressure
this protects fragile capillaries when arteriolar pressure gets too high
ventilation-perfusion coupling occurs when
poorly ventilated lung segments vasoconstrict
(hypoxia causes vasoconstriction)
what factors cause vasodilation –> active hyperemia in skeletal muscle
decrease in O2 levels in tissue
increased CO2 levels in tissue
decreased tissue pH
increased tissue temperature
K+ levels
chemical signals that result in vasodilation
- CO2
- K+ ions
- Adenosine
- Lactic acid
- nitric oxide
- Thromboxane
- prostacyclin
- histamine
-bradykinin
chemical signals that result in vasoconstriction
O2
endothelin-1
why are negative feedback loops w/in capillary beds so important?
b/c if capillary beds were to remain dilated it messes with the pressure gradient and therefore blood flow
what is active hyperemia?
blood flow response to increased tissue metabolic activity
what is reactive hyperemia?
blood flow response to a blood flow occlusion that causes the build up of waste products and an inability to deliver oxygen and nutrients
explain why blood flow through the coronary arteries is not consistent
blood flow through the coronary arteries increases during diastole and decreases during systole
- during diastole, vessels are NOT compressed so blood flow increases
- during systole, vessels are compressed so blood flow is reduced
explain nitric oxides role in adaptation to animals living at high altitude
O2 partial pressure is low at high altitudes and can cause chronic poor ventilation / pulmonary hypoxia
- big horn sheep & lama have chronically elevated production of nitric oxide (vasodilator)
what condition has the strongest control of arterial diameter
hpoxia
what does hypoxia lead to in lungs?
hypoxia in the lungs causes vasoconstriction of pulmonary arteries
what does hypoxia lead to in skeletal muscle?
vasodilation
active hyperemia in skeletal muscle causes what
vasodilation
what is active hyperemia?
blood flow response to an increase in tissue metabolic activity
what is reactive hyperemia?
blood flow in response to flow occlusion
what are local controls of blood flow
CO2, O2, pH
what is metabolic theory
local metabolic factors can cause increased blood flow to active muscles
the tissue supply of O2 matches the tissue demand for O2
explain ventilation-perfusion coupling
poorly ventilated lung segments vasoconstrict
what are myogenic responses (flow autoregulation)
arteriolar smooth muscles responds to changes in arteriolar BP
what is epinephrines’ effect on blood flow
epinephrine causes vasodilation via B2 adrenergic receptors, causing relaxation of smooth muscle at arterioles and skeletal muscle
what is angiotensin II effect on blood flow
angiostensin II is a potent vasoconstrictor, it acts on smooth muscle of arterioles
gets synthesized when BP is low
increases aldosterone synthesis
