Control of Peripheral Circulation

Question 1

What are continuous capillaries?

Answer 1

No clefts or pores (brain)
Clefts only (muscle and most other capillaries)

Question 2

What are fenestrated capillaries?

Answer 2

Clefts and pores (intestine, kidney) specialised for fluid exchange

Question 3

What are discontinuous capillaries?

Answer 3

Clefts and massive pores (liver)

Question 4

How does exchange take place in capillaries?

Answer 4

Mostly diffusion
-self regulating
-non-saturable
-non-polar substances across phospholipid membrane
- polar substances across clefts/pores

Carrier mediated transport

Question 5

What is hydrostatic pressure?

Answer 5

Force pushing liquid out of vessel

Question 6

What is osmotic (oncotic) pressure?

Answer 6

Force drawing liquid into vessel

Question 7

What are some causes of oedema?

Answer 7

Raised central venous pressure (ventricular failure)
Lymphatic obstruction
Hypoproteinaemia
Increased capillary permeability (inflammation, rheumatism)

Question 8

What is active metabolic hyperaemia?

Answer 8

Trigger is an increase in local metabolism
Paraffine signal released
Causes arteriolar dilatation

Question 9

What are the local intrinsic controls?

Answer 9

1. Active metabolic hyperaemia
2. Pressure autoregulation
3. Reactive hyperaemia
4. The injury response

Question 10

What are some central circulatory controls?

Answer 10

Sympathetic nerves
Releases noradrenaline binding to alpha1 receptors causing arteriolar constriction