Body Systems L2

Question 1

Body Fluids & their compartments?

Answer 1

• Total body water (TBW) -> 42 Litres
  1. Intracellular fluid (ICF) -> 25 litres
  2. Extracellular fluid (ECF) -> 17 litres
  i) Interstitial Fluid (ISF) -> 13 litres
  ii) Plasma -> 3 litres
  iii) Transcellular fluid -> 1 litre

Question 2

What is osmolality?

Answer 2

• Osmolality:
 Conc of solute in solvent.
 Same osmolality across all cellular fluid -> no movement of water.

Question 3

Name the types of membrane?

Answer 3

1. Plasma
2. Capillary endothelium
3. Epithelia

Question 4

Describe the plasma membrane.

Answer 4

• Permeability -> Highly selective
• High number of transport protein -> acceptance & removal of specific solutes
• Maintains optimal of intracellular environment.

Question 5

Describe the Capillary endothelium.

Answer 5

• Permeability -> Highly permeable in specific organs
• Thin lining of endothelial cells in blood vessels
• Maintains controlled regular flow of interstitial fluid
• > endothelial cells -> membrane

Question 6

Describe the Epithelia.

Answer 6

• Used for protection
• Layers of cells internally & externally cover organ & tissue.
• Used in absorption & secretion.

Question 7

List the types of transport in the plasma membrane.

Answer 7

 Impermeable phospholipid bilayer -> ions & polar molecules -> simple diffusion.
 Protein channels, carriers & pumps -> non-polar molecules.

Question 8

Describe the types of transporter channels in plasma membranes.

Answer 8

1. Channels – Passive transport -> down conc. gradient.
2. Carriers – Passive transport -> down conc. gradient.
   Binds to protein – changes shape – enables diffusion.
3. Pumps – Active transport -> against conc. gradient.
   Requires hydrolysis of ATP.

Question 9

Describe the types of carriers in plasma membranes.

Answer 9

1. Uniport – Facilitator
   - > Transports one ion species
2. Symporter – Co-transporter
   - > Moves 2 ion species together — (one +ve & one -ve.)
3. Antiporter – Exchanger
   - > One ion released and another replaces it (must be same charge eg. both +ve)

Question 10

Describe the role of the uniport in plasma membranes.

Answer 10

1. Uniport – Facilitator

- > Transports one ion species

Question 11

Describe the role of the symporter in plasma membranes.

Answer 11

2. Symporter – Co-transporter

- > Moves 2 ion species together — (one +ve & one -ve.)

Question 12

Describe the role of the antiporter in plasma membranes.

Answer 12

3. Antiporter – Exchanger

- > One ion released and another replaces it (must be same charge eg. both +ve)

Question 13

What are the functions of transport proteins?

Answer 13

• > Uptake of nutrients, substances & cofactors
• > Export of waste products.
• > Regulation of intracellular ions, pH & cell volume.

Question 14

What is the sodium-potassium pump responsible for?

Answer 14

• Na+/K+ pump -> gradient maintenance -> actively transports ions so everything else can diffuse passively (down conc. gradient)

Question 15

Distribution of water & solutes across the plasma membrane

Answer 15

See notes for following pics:

Question 16

Describe how Assymmetric distribution of K+ generates membrane potential in plasma membrane.

Answer 16

 (Nerve) Cells have electrical gradients -> membrane potentials -> enabling contraction of muscles/impulses.
 Resting membrane potential/electrical diff required.
 Achieved by diff. conc of K+ in ICF & ECF.
 If K+ channel opened, K+ -> down conc. gradient
 However also attracted to -ve charged proteins.
 Conc. gradient vs. attraction of ions at rest cause such resting
potential charges seen (mV) to be present.
 Therefore at equilibrium, high conc. of +ve ion in cell but cell
Itself negative relative to charge outside cell.

Question 17

Describe distribution of water in plasma membrane.

Answer 17

• Water moves down its osmotic conc from high to low conc by osmosis.
 Water isn’t actively transported -> too energetically expensive -> ions move & water follows.
 Cell volume regulated by ion channels, which then cause water to move osmotically.

Question 18

Describe distribution of solutes in the capillary endothelium.

Answer 18

2. Capillary Endothelium:
   - Solutes: -> conc. gradients.
3. Ions & organic solutes easily transported -> approx. equal distribution.
4. Proteins too large -> trapped in plasma. -> high conc. in plasma.

Question 19

Describe the water distribution in the capillary endothelium.

Answer 19

• Water distribution: -> determined by hydrostatic and osmotic forces
  1. Forced out of start of capillary network by pressure of heart rate.
  > Ions carried out of capillaries also.
  2. Pressure in plasma/capillaries decreases as more water forced out.
  3. Proteins trapped in plasma -> incr. conc & osmolality due to loss of water.
  4. Colloid (protein) osmotic pressure higher in plasma -> water diffuses back into capillaries by osmotic gradient.

Question 20

Describe epithelial transport of solutes using an example.

Answer 20

• Side of epithelial cell facing Inside -> Apical.
  Outside -> Basolateral.
• Cells -> selectively permeable
  -> Tight junctions -> nothing can pass between cells
  -> must go through
• 1. Na+ & glucose transporters transport ions from gut into
     epithelial cells.
     
     2. Creates osmotic gradient so water follows.
        3. Glucose transporter transports glucose down conc gradient.
  2. Na+/K+ pump -> Transport Na+ ions out of epithelial cell -> Water moves down osmotic gradient.
     -> Enables easier absorption of water using transportation of ions than water alone.

Question 21

Describe movement of water in epithelial transport.

Answer 21

• Water also flows in opp direction on basolateral side of epithelial cell.
  1. Na+/K+/Cl- co-transporter takes up ions.
  2. Water moves into intestinal epithelial cell down osmotic gradient.
  3. Cl- channel on apical side of epithelial cell -> enables diffusion of Cl into gut lumen.
  4. Water moves into gut lumen down osmotic gradient.
• > Enables diffusion of water into small intestine -> aid physical transport of food to lower intestine. -> Reabsorbed in large intestine.