Lecture 13- local circulation control and capillary exchange

Question 1

What is the overall principle of net filtration pressure?

Answer 1

Capillary hydrostatic pressure pushes water and solutes out of capillaries into the ISF. This is opposed by osmotic forces pushing into the capillaries.

Question 2

What is the formular for net filtration pressure?

Answer 2

NFP= Net hydrostatic pressure- Net colloid osmotic pressure

Question 3

What is the formula for net hydrostatic pressure?

What are the values?

Answer 3

NHP= capillary hydrostatic pressure - Interstitital fluid hydrsotatic pressure.

The CHP is 35mmHg at the arterial end and 18mmHg at the venous end. The IHP is negligable so taken as zero.

Question 4

What is the formular for net colloid osmotic pressure?

What are the values?

Answer 4

NCOP= Blood colloid osmotic pressure- ISF colloid osmotic pressure

NCOP = BCOP - ISF COP

BCOP= 25 mmHg. ISFCOP is negligable

Question 5

What is the net filtration pressure at the arterial end of the capillary?

Answer 5

+10 mmHg because the filtration 35 mmHg going out and 25 osmotic going in. Overall 10mmHg giong out

Question 6

What is the net filtration pressure at the venous end?

Answer 6

-7 mmHg.

The filtration pressure is 18 mmHg going out and 25 osmotic pressure going in . Overall 7 going in. -7 filtration out.

Question 7

What affect does adrenaline have on coronary circulation?

Answer 7

• Promotes vasodilation of coronary vessels
• Increase HR and strength of contractions
• Coronary blood flow increases when elsewhere in the body vasoconstriction predominates

Question 8

Why does more filtration happen in the capillary than absorption?

Answer 8

The max filtration pressure is greater than the max absorption pressure.

So the transition point when net filtration pressure = 0 is not in the middle, furthr towards the venous end of the capillary.

Question 9

What is special about pulmonary ciculation when O2 levels are low?

Answer 9

Low O2 promotes vasoconstriction. Pulmonary vessels constrict to shunt O2 to the alveoli

Question 10

What is intrinsic control?

Answer 10

Autoregulation by the blood vessels

Question 11

What happens in metabolic control? When metabolism increases

Answer 11

1. There’s a decrease in O2, increase in CO2, decreased pH and increased K+
2. Dilation of arterioles
3. Increased blood flow
4. Back to normal

Question 12

What’s the exception to the usual metabolic control?

Answer 12

Pulmonary circulation. Increased O2 and decreased CO2 causes vasodilation