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48 Cards in this Set

  • Front
  • Back
Blood vessels are well innervated by sympathetic nerves.
Vessels dont have parasymp. innervation.
False. Some do have.
What is the main agonist of the symp. NS on blood vessels?
What acts on blood vessels from the para. NS?
Where do you get limited innervation of blood vessels by the parasymp. NS ?
Salivary glands
What happens at alpha adrenoceptors in blood vessels?
Constriction(by both epi and norad)
What happens at B2 adrenoceptors in blood vessels?
Change in arteriolar tone offers most resistance change.
Arteriolar response to symp. activation depends on
Adrenoceptor population
-Alpha constriction in skin,coronary,brain,viscera
-beta dilatation in skeletal muscle
At which adrenoceptor is Norad a better agonist?
Alpha adrenoceptors.---> vasoconstriction in BV.
Adrenaline in low dose causes
Dilatation(skeletal muscles)
Adrenaline in high doses causes
Vasoconstriction(increase BP)
Isoprenaline acts only on Beta adrenoceptors.
What are the 2 types of adrenoceptors found in BV?
Alpha and beta
What is Prazosin?
Alpha adrenoceptor antagonist ---> vasodilatation
Propanolol is
Beta antagonist causing vasoconstriction.
Right Coronary artery supplies the right atrium and right ventricle and likewise for left coronary artery.
True,with some overlap.(right dominant in 50 % of population)
What are the factors that influence coronary blood flow?
When does most of blood flow through left coronary arteries?
During diastole.(extravascular forces prevent blood flow)
Right coronary blood flow is max. during systole.
What does symp. stimulation do to coronary blood flow?
Increase coronary blood flow
What is the direct effect of symp. NS on coronary blood flow?
Vasoconstriction because more alpha receptors.
WHat is the INDIRECT effect of symp. stimulation on coronary blood flow?
Increase cardiac contractility (Beta 1) and extravascular compression + decrease diastole impairing flow----> this increases O2 consumption causing metabolic vasodilatation---> increase flow.
What is the parasymp. effect on coronary blood flow?
Negligible direct effect except for indirect effect of bradycardia which leads to decreased flow.
What is the primary regulator of coronary arterial tone?
Metabolic control
CBF is in proportion to the O2 requirements of the myocardium.
What is active hyperemia?
Increase in blood flow in response to increased metabolic demands
O2 is efficiently removed by heart from blood.
True(65-70 % at rest)
What are the mediators of metabolic vasodilatation?
Adenosine(breakdown of ATP)
lactic acid
There is a linear relationship between CBF and O2 metabolic demands.
True(doesnt happen in other organs as they will initially extract more O2)
What is the major influence of blood flow to the skin?
Temperature regulation.
What are the 2 types of resistance vessels in skin?
-AV anastomoses(shunt blood from arterioles to venules bypassing capillaries)
If AV anastomoses open up, large blood flow THROUGH skin but not large blood flow TO skin.
AV anastomosoes contain thin muscular walls.
False.Thick muscular walls.
AV anastomoses contain rich SYMP. innervation.
Nerve interruption to skin causes
Maximum dilatation
What does nerve stimulation cause to skin?
Total occlusion
Where do you find AV anastomoses?
Closing blood flow to anastomoses will not stop flow to skin
Because of capillaries.
Cutaneous blood flow
-normal:400 ml/min
-severe cold : 50
-severe heat : 2800
What regulate body temp. ?
What happens at normal temp. ?
Sympathetic constriction
At high temp.,
Decreased symp. outflow with vasodilatation.
Skeletal muscle blood flow has
large capacity to respond to exercise
-3-4 ml/min per 100 g at REST
-50-80 ml/min per 100 g during EXERCISE.(CO incr. by 4)
At rest,what determines skeletal muscle blood flow?
During exercise,what determines skeletal muscle bloow flow?
-O2 deficiency
-release of local dilator factors(adenosine,K+,H+,CO2)
-circulating epi--->stimulates B2 adrenoceptors---> vasodilatation.
Neural control in skeletal muscles in via
Norad. released from symp. nerves causing constriction by activating Alpha adrenoceptors.
-reduced baroreceptor stimulation causes vasoconstriction.
At rest, there is not much circulating adrenaline