L07-* Elastic arteries and haemodynamics Flashcards
What are the main functions of elastic arteries?
To dampen the pulsetile pressure and ensure continuous flow
Ensures blood pressure is maintained during diastole
How is mean arterial blood pressure calculated?
Mean ABP = (SP+2DP)/3
What is the equation for compliance?
Compliance=change in volume/change in pressure
What effect does ageing have on pulse pressure?
As the compliance of the arteries decreases with age then the systolic pressure increases as with each contraction the artery cannot stretch as much. A lower DP is also seen as the artery does not recoil as much so DP falls further.
What determines the resistance to flow through a single vessel?
vessel length
radius
Blood viscocity
The flow is directly proportional radius^4
What is the most efficient form of flow through vessels?
Laminar flow
How do blood pressure cuffs work?
They create turbulent flow that causes Korotcoff sounds
What two main factors determine DP?
Arteriolar resistance
HR - very high HR increases DP
What are the effects of endothelial influences on vessel diameter?
the vessels are tonically dilated by substances released by the endothelial cells that act on the smooth muscles.e.g. NO and prostaglandins
What is the mechanism for the release of vasodilators locally from the endothelium?
Increase in shear stress causes release of NO and prostaglandins, also ach release has the same effect.
What is the autonomic control of blood vessels called? which tissues does this act in the most?
Myogenic tone, this works strongest in cerebral and renal tissues
What is the cerebral autoregulatory range?
60-180mmHg
How does metabolic influence effect vessel diameter?
increased metabolic activity causes vasodilation in order to increase blood flow.
Which receptors cause vasodilation and vasoconstriction in responce to sympathetic activity?
Alpha 1 receptors cause vasoconstriction.
beta 2 receptors cause vasodilation which only act in skeletal muscles (sympathetic bonds weakly)
In increased sympathetic activity the alpha receptors predominate
Which receptors cause vasodilation and vasoconstriction in responce to circulating adrenaline?
Adrenaline binds weakly to alpha 1 receptors that cause vasoconstriction.
Beta 2 receptors are bound strongly by circulating adrenaline.
beta 2 are only present in skeletal muscle so this is where the main effect of adrenaline acts.
