Fluid Compartments And Solutes

Question 1

How do ion concentrations in the muscle and plasma compare?

Answer 1

Na+: p(150) m(10)

K+: p(5) m(150)

Ca2+: p(2) m(10^-4)

Cl-: p(110) m(5)

Organic phosphates - : p(5) m(130)

Protein 17- : p(1) m(2)

pH: p(7.4) m(7.1)

THEIR OSMARITY IS BOTH 285

Question 2

Which way does water move in osmosis?

Answer 2

Towards an area of higher osmolarity (concentration of all solutes)

Low to high water concentration

Question 3

What is an osmole?

Answer 3

The number of miles of absolute that contribute to the osmotic pressure of a solution

Eg NaCl at 150 mmol/L

Because there are two ions in it it’s 150 x2

300 mosmol/L

Question 4

Why is osmolarity pretty unreliable?

Answer 4

Because it depends on so many things

If the osmolarity inside a cell is greater than outside, the cell could remain the same, swell, or rupture, depending on what the membrane is permeable to etc

Instead we use Tonicity

Question 5

What is tonicity?

Answer 5

Defines the “strength” of a solution as it effects the final cell volume. Tonicity depends on both membrane permeability and the composition of the solution

Question 6

What does a hypertonic solution mean?

Answer 6

Osmolarity outside > inside

So water moves out and the cell shrinks

Question 7

What is a hypotonic solution?

Answer 7

Osmolarity outside

Question 8

What is an isotonic solution?

Answer 8

Osmolarity inside = outside

Question 9

What prevents cells from bursting in a cell that has a much higher osmolarity due to proteins in the cell than out, the membrane is permeable to water?

Answer 9

The sodium potassium ATPase

This maintains the conc of Na+ ions much higher outside the cell than inside

The ATPase makes the membrane effectively “impermeable” to sodium ions as and that diffuse in are actively pumped out again

Question 10

What are the methods of different substances of moving across the phospholipid bilayer?

Answer 10

Passive: 
Simple diffusion (gasses and hydrophobic molecules (steroids))

Channel mediated

Transported mediated

Active:
Active transport using a transporter

Question 11

Why must tissue preservation solutions be used when transplanting organs?

Answer 11

To prevent ischaemic changes to the organ during transportation it is cooled to 4 degrees C

However below 15 C the Na/K ATPase stops working (there is also a lack of circulation and therefore oxygen). This could lead to an influx of sodium ions (and Cl-). Water will also enter as K+ leaves. This could cause cells to swell leading to cell death

University of Wisconsin solution (UW) can be perfused to present this

There is a lack of Sodium and chloride ions so they can’t enter the cell. Presence of extracellular impermanent solutes. Presence of macro molecular colloids (starch)

Question 12

How much plasma leaks out of the blood vessels a day?

Answer 12

8L

The volume of blood plasma is about 3L .the entire plasma volume must pass into the interstitial space and back into the blood once every 9 hours

Question 13

How do molecules travel across the endothelium of capillaries?

Answer 13

LIPID SOLUBLE SUBSTANCES - pass through the cell membrane of the endothelium

SMALL WATER SOlUBLE - pass through the pores between the endothelial cells

PLASMA PROTEINS - can’t cross the endothelium and cannot pass through the pores

EXCHANGEABLE PROTEINS - moved across by vesicular transport

Question 14

What is the colloidal osmotic pressure?

Answer 14

In normal capillaries the concentration of plasma proteins in the blood is higher than in outside the capillary

Question 15

What opposes the colloidal osmotic pressure?

Answer 15

Hydrostatic pressure caused by blood flow is higher in the capillary than outside. This tends to push molecules through the pores

Question 16

What is a leaky capillary and what can it lead to?

Answer 16

May have increased pore size so plasma proteins can leak out. This reduces the COP

This means hydrostatic pressure&raquo_space;> osmotic pressures

So more fluid leaves the capillary so fluid accumulated in the interstitial space

This is called oedema (if the lymphatic system can’t drain it)

Question 17

How is fluid in the interstitial space drained?

Answer 17

By lymphatic vessels. These are blind ended and have a low internal pressure so fluid flows into these

Question 18

Where does fluid in the lymph vessels go?

Answer 18

Returns to circulation either via the lymphatic ducts (subclavian region) or via lymph nodes

When leakage of fluid into the interstitial space exceeds the lymphatic capacity, oedema occurs

This often occurs in inflammation