Reguation of arteriolar resistance Flashcards
What is the MAP equation?
MAP = CO X TPR
Does the binding or norepinephrine to A1 receptors on arteries cause dilatation or constriction?
constriction
does sympathetic stimulation cause an increase or decrease in TPR and how?
sympathetic stimulation causes arteriolar constriction which decreases flow through that tissue and increases TPR
what affect does parasympathetic nerves have on arteriolar resistance?
no control
how does epinephrine cause arteriolar dilatation?
epinephrine binds to B2 receptors therefore increasing flow and decreasing TPR
what hormone does the sympathetic nerves release?
norepinephrine
where would epinephrine activate B2 receptors in vessels?
skeletal and cardiac muscle
what is ADH also referred to as?
Vasopressin
does angiotensin II cause an increase or decrease in TPR?
Angiotensin II is activated by a decreased distension of afferent arterioles and decrease in blood volume so causes arteriolar constriction and hus increae in TPR
what are the local (intrinsic) control of arteriolar resistance (TPR)
active (metabolic) autoregulation
pressure (flow) autoregulation
reactive hyperaemia
the injury response
describe the active (metabolic) autoregulation of resistance.
when there is an increase in activity the concentration of metabolites increases
this releases EDRF which causes arteriolar dilatation
describe the pressure (flow) autoregulation of resistance.
a decrease in MAP causes a decrease inflow so metabolites accumulate which trigger the release of EDGF
this causes arterioles to dilate and metabolites are returned to normal
describe the reactive hyperaemia control of resistance.
accumulation/blockage of blood supply causes a subsequent increase in blood flow
(a cut off of blood supply causes a subsequent increase in blood flow once it is restored, thereby reducing TPR to restore flow)
describe the injury response control of resistance.
injury causes release of peptides which stimulate mast cells to release histamine
histamine causes arterioles to dilate and therefore reduce TPR and increase blood flow
in the coronary circulation , what type of intrinsic control of resistance does it show?
the coronary circulation shows great active hyperaemia.
this is because during systole the blood supply to the heart is cut off. therefore during diastole there is subsequent increase in blood flow to compensate.
