Regulation of Arteriolar Resistance Flashcards
Justify the importance of Poiseuille’s Law in relation to the control of resistance and blood flow
Varying the radius of resistance vessels is used to control flow.
Varying the radius of resistance vessels is also used to control total peripheral resistance (TPR) & therefore regulate mean arterial pressure (MAP).
What is used to control the flow through individual vascular bed ?
The varying radius of the arterioles
What is metabolic hyperaemia ?
An increase in organ blood flow associated with an increase in metabolic activity.
What acts on the artery to cause dilation during hyperaemia ?
EDRF
What is pressure auto-regulation ?
Occurs when there is a drop in MAP which causes an accumulation of metabolites. EDRF is then released to dilate artery and wash away metabolites.
What is reactive hyperaemia ?
An extreme version of pressure auto-regulation after an occlusion has occurred
Explain the injury response
When a site in the body is injured the arterioles dilate allowing increased blood flow to injured site and also allows passage of leukocytes to injured area
What are the three factors that affect arteriole tone ?
Neural, hormonal and local
What are the neural factors that affect the arterioles ?
Sympathetic: Nor-adrenaline acts on the alpha 1 receptors and causes arteriole constriction which causes TPR to increase and flow through the tissues to decrease.
Parasympathetic: No affect
What are the 5 hormonal controls with regards to arteriole tone ?
Epinephrine
Angiotensin II
Vasopressin
ANP and BNP
Where does epinephrine come from and how does it affect the arterioles ?
Epinephrine gets released from the adrenal medulla and will act on alpha 1 receptors to cause arteriole constriction causing decreased flow and an increase in total peripheral resistance
how does cardiac and skeletal muscle react to epinephrine ?
Epinephrine also activates Beta 2 receptors in skeletal and cardiac muscle which causes arteriole dilation which would increase flow and decrease TPR.
Where does angiotensin II come from and how does it affect the arterioles ?
Is produced in response to low blood volume signalled by the kidneys. It causes arteriole constriction which will increase TPR
How does ANP and BNP effect arterioles ?
ANP and BNP act in response to an increase in blood volume and therefore cause arteriolar dilation and a decrease in TPR
