Regulation of Arteriolar Resistance Flashcards
How is blood flow controlled and directed?
By varying the radius of resistance vessels
What controls total peripheral resistance and regulates mean arterial pressure?
Varying the radius of resistance vessels
Changes in the radius of which blood vessels has the biggest effect of the circulation?
Arterioles
How is blood vessel radius controlled?
Smooth muscles surrounding the vessels
What are the two levels of control over the smooth muscle surrounding the arterioles?
Intrinsic mechanisms
Extrinsic mechanisms
How do sympathetic nerves effect extrinsic control of smooth muscles?
Release norepinephrine
binds to alpha-1-receptors
Causes arteriolar constriction
Decreased flow and increases total peripheral resistance
How do parasympathetic nerves effect extrinsic control of smooth muscles?
They do not have an effect usually
How is extrinsic control of smooth muscles done hormonally?
Epinephrine is released from the adrenal medulla and acts as it does in the sympathetic system
However, in some tissues such as skeletal and cardiac muscle, it also activates beta-2-receptors which cases arteriolar dilation, increased flow and deceases TPR
What is produced in response to low blood volume?
Angiotensin II
What effect does angiotensin II have on blood flow?
Arteriolar constriction and increases TPR
What is released in response to low blood volume?
Vasopressin the antidiuretic hormone
What effect does Vasopressin have on blood flow?
Arteriolar constriction which increases TPR
What is released in response to high blood volume?
Atrial natriuretic peptide
Brain natriuretic peptide
What effect do Atrial natriuretic peptide and Brain natriuretic peptide have on blood flow?
Arteriolar dilation which decreases TPR
What are the 4 methods of Intrinsic control of smooth muscles?
- Active hyperaemia
- Pressure autoregulation
- Reactive hyperaemia
- The injury response
How does active hyperaemia work?
Increased metabolite activity increases metabolite concentration which releases EDRF. This causes arteriolar dilation to increase flow and wash out metabolites
How does pressure auto regulation work?
Decrease MAP causes decreased flow so metabolites accumulate. This triggers the release of EDRF which causes arteriolar dilation and restores flow to normal
How does reactive hyperaemia work?
Occlusion of blood supply causes a subsequent increase in blood flow
