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Cardiopulmonary 15
Local Control of Peripheral Circulation
21
Medical
Graduate
12/11/2012

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Cards

Term
which organs use the most oxygen?
Definition
the heart and the brain
Term
what are the three mechanisms for controlling local blood flow?
Definition
metabolic regulation
autoregulation
sheer stress induced vasodilation
Term
define active / reactive hyperemia.
Definition
active - increase in blood flow to a region due to increased metabolite production

reactive - increased blood flow to an area due to oxygen debt after a pause in flow
Term
describe the metabolic mechanism for increasing blood flow to an area.
Definition
metabolites cause proportional vasodilation at the precapillary bed to remove the increased metabolites
Term
describe the role of autoregulation of blood flow as it relates with changes in perfusion pressure.
Definition
the body has a set blood flow, and changes in perfusion pressure (such as IV infusion) cause rapid changes in flow. the body adjusts to return the flow back to normal despite the change in pressure. this is because the body was already in a flow equilibrium
Term
define transmural pressure.
Definition
the difference in pressure inside and outside a wall.
Term
define the myogenic hypothesis and how does it relate to changes in transmural pressure?
Definition
it states that an increase in tension on smooth muscle causes it to contract, and a decrease in tension causes it to relax

an increase in the transmural pressure due to an increase in flow causes the smooth muscle to constrict and therefore reduce vessel diameter
Term
is myogenic regulation endothelium dependent or independent and why?
Definition
independent, because it is caused by the stretch of the smooth muscle regardless of the presence of the endothelium
Term
what causes the myogenic regulatory response?
Definition
the stretch of the muscle cells cause changes in the conductance of the ion channels which leads to depolarization and contraction
Term
describe shear stress induced vasodilation and how is it caused?
Definition
it is an endothelium dependent mechanism in which an increase in flow causes vasodilation due to increased NO production, this mechanism is regardless of pressure
Term
how does exercise affect upstream vessel diameter?
Definition
increased metabolite production causes downstream vasodilation, this in turn causes an increase in flow up and downstream. the increased flow upstream leads to an increase in sheer stress which then causes upstream vasodilation in order to support more flow to the exercising muscle
Term
what organs are predominantly under metabolic control?
Definition
brain, heart, skeletal muscles
Term
what organs are predominantly under sympathetic/neurogenic control?
Definition
skin, kidney, splanchnic organs
Term
at the sympathetic neuro-effector junction what determines the type of response?
Definition
the receptor and not the neurotransmitter
Term
what type of vascular response is caused by alpha 1 and 2 receptors and why?
Definition
they cause vasoconstriction due to an increase in intracellular Ca
Term
what type of vascular response is caused by beta 1 receptors and why?
Definition
they cause vasoconstriction due to an increase in intracellular Ca, and they increase cardiac contractility and HR
Term
what type of vascular response is caused by beta 2 receptors and why?
Definition
they cause vasodilation due to a decrease in intracellular Ca
Term
describe the difference between receptor affinities of epinephrine and norepinephrine.
Definition
epi can bind all three receptors, but binds strongest to beta 2 receptors, and NE only binds to alpha 1 and beta 1 receptors
Term
what is the main difference between smooth muscle cell receptors and neuronal cell receptors?
Definition
smooth muscle cells have muscarinic acid receptors for Ach, whereas neuronal cells have nicatinic acid receptors
Term
what affect does acetylcholine have on the heart?
Definition
it causes a decrease in HR and conduction velocity
Term
what affect does acetylcholine have on the blood vessels and where is this affect seen?
Definition
it causes vasodilation, but is only seen in the distal end of the colon and genitals due to their innervation by the parasympathetic nervous system
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