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40 Cards in this Set

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distributed
Blood does NOT flow equally to all organs but instead gets ____________ among the organs based on need.
Extrinsic control mechanisms
local control.
________ _________ _________ provide adequate arterial pressure for all organs in the systemic circuit, but only an individual organ or tissue can really "know" how much blood it needs at any given time, and it so it regulates its own blood flow thorugh _______ ________.
vascular resistance
Changes in the distribution of blood flow to organs - that is, changes in the percentage of cardiac output supplied to each organ - due to changes in _________ __________ of individual organs.
vascular resistance
The __________ __________ of an organ (or tissue) is altered by the contraction or relaxation of smooth muscle in arterioles (and small arteries).
vasoconstrict
vasodilate
Arterioles can _________ or _________ in response to intrinsic factors, thereby changing the resistance to blood flow.
Intrinsic control mechanisms
___________ _______ _________ regulate NOT only the distribution of blood flow among the organs, but also the distribution of blood flow w/in the organs.
Intrinsic
_________ mechanisms are responsible for the sharing of flow among cap beds.
heart, brain and skeletal muscle
Intrinsic control is especially important in regulating blood flow to the _______, _______, and ________ ________.
1) Neural mechanisms play only a minor role in regulating blood flow to the heart & brain.
2) Metabolic activity in the heart & skeletal muscles can vary greatly, changing there demands for 02 and nutrients.
What are the 2 reason why intrinsic mechanisms are important?
metabolic activity
________ ________ of the brain as a whole is relatively constant, activity varies from region to region w/in the brain.
increase
decreasing
Intrinsic mechanisms work on a continual basis to _________ blood flow to regions that are becoming more active while reducing flow to those whose activity is __________.
relaxation
contraction
Intrinsic control of organ flow is accomplished through __________ or __________ of smooth muscle in arterioles, which control the flow through individual cap beds w/in an organ or tissue.
vascular smooth muscle
What senses whether blood flow is adequate or not?
1. changes in metabolic activity
2. changes in blood flow
3. stretch of arteriolar smooth muscle
4. local chemical messengers
What are the 4 factors that vascular muscle responds to regulation?
extracellular fluid
metabolic activity
Vascular smooth muscle cells in arterioles are sensitive to condition in __________ ______ & respond to changes in the concentrations of a wide variety of chemical substances, including 02, CO2, K+ ions, H+ ions, and others. These change in concentrations occur as a result _________ ________.
contracts
relaxes
Arteriolar smooth muscle either ________ or _________ depending on whether concentrations of particular substances rises or falls.
vasodilation
vasoconstriction
Changes associated w/ increased metabolic activity generally cause __________, whereas changes associated with decreased metabolic activity induce ___________.
ischemia
blood flow is insufficient to keep up w/ metabolic demand
02
c02
The decrease in _________ & the increase in ________ ________ both act on arteriolar smooth muscle, causing it to relax.
vascular resistance
When the muscle relaxes, ________ _________ in tissue drops, and blood flow in that region increases.
active hyperemia
higher than normal rate of blood flow following metabolic activity.
02
CO2
________ delivery to the tissue & _______ _______ removal from the tissue increases & eventually a new steady state is acheived.
active hyperemia
nerves or hormones
______ _________ is an example of intrinsic control, because the change of blood flow has a direct affect of the reduced oxygen & elevated C02 on arterioles themselves, & that no ______ or _________ are involved.
Tissue 02
metabolic concentration
_______ _______ & __________ ____________ can also change as a result of changes in blood flow.
vasodilation
vascular resistance
If blood flow is blocked, the 02 concentration falls and the CO2 production exceed rates of delivery & removal. Both induce _________ & a reduction in _________ _________ tends to increase in blood flow.
Reactive hyperemia
an increase in blood flow in response to a previous reduction in blood flow.
reactive hyperemia
The basic mechanism underlying ________ _________ is the same as that for active hyperemia - decreases in tissue oxygen & increases in metabolic concentrations induce vasodilations & an increase in blood flow.
concentration
The only difference in reactive and active hyperemia in the CAUSE of the changes in _____________.
reverse
intrinsic control mechanisms
The sequence of events occuring in reactive hyperemia also works in _________ : if blood flow rise above what is required for metabolic needs, ________ ________ __________ will induce vasoconstriction & a reduction in blood flow.
stretch - sensitive fibers
They are responsive to stretch which occurs when pressure of blood w/in the arterioles increases
myogenic response
a change in vascular resistance that occurs in response to stretch of blood vessels, and that does NOT requirs the action of sympathetic nerves, bloodbourne, or other chemical agents.
Perfussion pressure
the pressure gradient that drives blood flow through a given organ or tissue
Negative feedback loop
Myogenic control of vascular resistance in response to change in perfusion pressure is similar to the other intrinsic control mechanisms involves a _________ _________ _____.
flow autoregulation
local regulation that tends to keep blood flow constant.
vascular smooth muscle
Contractile activity of __________ ______ _______ is also affected by a variety of chemical substances, most of which are secreted by blood vessels endothelial cells or by cells in surronding tissues.
Nitric oxide
released on a continual basis by endothelial cells in arterioles & act on smooth muscle to promote vasodilation.
bradykinin
histamine
substances produces by inflamed tissues, such as _________ & _________, stimulate nitric oxide synthesis. The resulting increase in blood flow accounts for redness of inflamed areas.
Prostacyclin
an eicosanoid that functions in preventing blood clots

vasodilator
Adensine
an important vasodilator in the coronary arteries.
Endothelin -1
substance that promote vasoconstriction