Regulation of arteriolar resistance

Question 1

What did Darcy’s law tell us?

Answer 1

Flow = mean pressure/resistance

Question 2

What is Poisieuilles law?

Answer 2

It states that the flow (Q) of fluid or resistance is related to a number of factors: the viscosity (n) of the fluid, the pressure gradient across the tubing (P), and the length (L) and diameter(r) of the tubing.

Question 3

What extrinsic factors influence blood flow and resistance?

Answer 3

Sympathetic (parasympathetic has no effect)
Adrenaline
Angiotensin II
ADH/vasopressin
Atrial natriuretic peptide
Brain natriuretic peptide

Question 4

Name 4 local intrinsic factors which affect blood flow and resistance

Answer 4

Active metabolic hyperaemia
Pressure flow regulation
Reactive hyperaemia
Injury response

Question 5

Describe active metabolic hyperaemia

Answer 5

Increased metabolic activity leads to increased concentration of metabolites locally, causing the release of EDRF (endothelium derived relaxation factor) which dilates vessels to increase flow and wash it all out

Question 6

Describe pressure flow regulation

Answer 6

When BP drops, flow slows down leading to the accumulation of metabolites. This increases the release of EDRF, vessels dilate and flow increases

Question 7

Describe reactive hyperaemia

Answer 7

Transient increase in blood flow following a brief period of schema

Question 8

Describe the injury response

Answer 8

When skin is breached, noiceptor C fibres detect damage and relay information to the brain, causing the release of protein P. Thus acts on mast cells to release histamine, causing smooth muscle relaxation and increases permeability of the blood vessels. This increases blood flow to aid entry of WBCs to try and clear any invading pathogens, and causes swelling and oedema