Regulation of arteriolar resistance Flashcards
What is the equation used to calculate mean arterial pressure?
MAP = CO x TPR
What do Darcy and Poiseuille’s laws suggest?
Varying radius of arterioles is used to control flow through individual vascular beds
BUT varying arteriolar radius also affects MAP
What does reduced resistance in vascular beds mean for the MAP?
The MAP becomes reduced
What are the two mechanisms used to control the smooth muscle surrounding arterioles?
Intrinsic mechanisms
Extrinsic mechanisms
What are the two types of extrinsic control?
Neural
Hormonal
What does the sympathetic response do in terms of extrinsic control on smooth muscle surrounding the arterioles?
Releases noradrenaline
Binds to alpha-1 receptors
Causes arteriolar constriction
Increases TPR
What do ADH and angiotensin II do in terms of extrinsic control of smooth muscle surrounding arterioles?
Cause arteriolar constriction
Increase TPR
ADH and angiotensin II are both released in response to what?
Low blood volume
What are the 4 main local (intrinsic) controls?
Active hyperaeia
Pressure (flow) autoregulation
Reactive hyperaemia
Injury response
What does the release of histamine do in response to injury?
Causes dilation
Which in turn increases blood flow and permeability
Reactive hyperaemia could be seen as an extreme version of what?
Pressure autoregulation
In coronary circulation, which receptors are expressed?
Beta-2
What does pressure autoregulation ensure?
Tissues maintain blood supply despite the changes in mean arterial pressure
In pulmonary circulations what does the decrease in oxygen cause?
Arteriolar constriction
In renal circulation, what does filtration depend on?
Pressure
