Regional Circulations Flashcards
(47 cards)
What does hyperemia mean?
Increased blood flow
What are extrinsic mechanisms that regulate blood flow?
Hormonal/neural control
What is “the contractile state of a resistance vessel?”
Tone
What is basal tone?
The state of partial contraction independent of metabolic and neural mechanisms
A result of the properties of the vessel vascular smooth muscle
(If you removed the vessel from all other inputs and put it in a chamber, how much tone you would have)
How does the resting tone of vessels differ from the basal tone?
The resting tone of vessels is higher than what their basal tone would be due to tonic sympathetic nerve activity
What is active vasoconstriction?
A decrease in vessel diameter due to sympathetic stimulation or constrictor hormones
What is active vasodilation?
Increase in vessel diameter due to dilator nerves, hormones, or local factoss
What is passive vasoconstriction?
A return towards resting state from a dilated state due to the removal of active dilator influences
What is passive vasodilation?
A return towards resting state from a constricted state due to the removal of active constrictor influences
Is autoregulation dependent on neural input?
No it is entirely independent of neural input
What is autoregulation/
A tissue doing what it has to do to maintain a steady-state pressure despite fluctuation in blood pressure
What are the 2 theories that can explain how tissues auto regulate their blood flow to a steady state despite fluctuations in blood pressure?
Metabolic theory
Myogenic theory
How does the metabolic theory explain how tissues autoregulate their blood flow?
As perfusion pressure increases, vasodilator metabolites are washed out of the surrounding fluid causing passive vasoconstriction and an increase in resistance (and conversely, metabolites accumulate when pressure falls)
How does the myogenic theory explain how tissues autoregulate their blood flow?
Increases in pressure causes the walls to stretch, which opens up calcium channels, which causes vascular smooth muscle to contract, and increasing resistance
(And conversely, vasodilation occurs when pressure falls and wall tension decreases)
What are some examples of metabolic vasodilators?
K+
CO2
Local hypoxia (sort of)
Lactic acid
H+
Phosphate ions
Prostaglandins
Adenosine
Adenine nucleotides
How does active tissue tell the arterioles that it needs more blood and they need to dilate?
Active tissue will release metabolic vasodilators
What is active hyperemia?
Blood flow is adjusted to meet the metabolic demands of the tissue
-accomplished via an increased production of vasodilator metabolites
What is reactive hyperemia?
The increase in blood flow to a tissue that occurs in response to transient ischemia
Caused by the local buildup of vasodilator metabolites during the ischemic phase
Duration and magnitude of reactive hyperemia are proportional to the ______
Length of time of the ischemia
Does reactive hyperemia happen all the time everyday
Yes for example when you bench press at the gym and occlude blood flow momentarily, that qualifies as transient ischemia, and metabolic vasodilators will accumulate
What happens if norepinephrine binds to an a-1 adrenergic receptor on vascular smooth muscle of resistance vessels and veins?
vasoconstriction
What happens if you withdraw sympathetic activity?
Passive vasodilation
Which receptor does epinephrine bind to to cause contraction?
a-1 receptors
Which receptor does epinephrine bind to to cause relaxation, and where are they mainly located?
B2-adrenergic receptors mainly located in skeletal muscle
