L11 - regional control of blood flow Flashcards
list the ways blood flow can be increased / decreased
- ANS
- active hyperaemia (metabolic)
- functional hyperaemia (metabolic)
- reactive hyperaemia (metabolic)
- flow auto regulation (metabolic and pressure)
- endocrine (hormonal)
- paracrine
- PO2
define hyperaemia
increased blood flow
define active hyperaemia
blood flow increases to a tissue because it is metabolically active and needs more O2 / fuel
define functional hyperaemia
when an organs normal function requires cyclical drops in pressure, so flow must increase cyclically to compensate
define reactive hyperaemia
blood flow increases to compensate for prolonged periods of reduced pressure and flow
explain process of active hyperaemia
- increased work being done in muscle = more O2 and glucose consumption
- decrease PO2
increased metabolite production
increased heat
increased PCO2 (decreased pH) - local vasodilation
- increased blood flow to that tissue
define flow auto regulation
tissue that can regulate its own blood flow
what does higher tone mean?
higher degree of arteriole contraction
what two factors control flow auto regulation (and in what way)
- pressure (increased pressure = decreased flow)
2. metabolic (metabolite accumulation = increased flow)
describe process of flow autoregulating by pressure
- increased pressure stretches arterioles
- increases smooth muscle tone
- local vasoconstriction
- decreased flow
why is flow auto-regulation important?
exercise increases CO and therefore flow throughout whole body, but some tissues want to maintain normal flow
describe process of flow autoregulating by metabolites
- normal tissue function involves cyclical compression of arterioles (eg heart)
- causes cyclical decrease in
blood pressure
blood flow
O2
and cyclical increase in
metabolite accumulation - cyclical local vasodilation
what is functional hyperaemia the same as
flow auto regulation by metabolites
what is reactive hyperaemia a form of?
flow auto regulation by metabolites
describe process of reactive hyperaemia (flow autoregulation)
- prolonged period of reduced blood pressure and flow leads to
increased metabolite accumulation
decreased O2 - exaggerated local vasodilation
what are the functions of hormonal control of regional blood flow
- regulate blood flow to metabolic demand (like other methods)
- maintain MABP, blood vol and osmolarity etc)
what effect does adrenaline have on skeletal muscle and why
vasodilation (binds to b receptors)