W7 - Fluid, Electrolyte and Acid-Base Homeostasis

Question 1

What are Metabolic acidosis and Metabolic alkalosis and how are they compensated?

Answer 1

Too high or low pH that the renal system cannot cope with so compensated by respiratory mechanisms

Question 2

What are Respiratory acidosis & Respiratory alkalosis and how are they compensated?

Answer 2

Too low or too high pH caused by the respiratory system (?) compensated by renal system

Question 3

What is alkalosis and what does it result in?

Answer 3

systemic arterial blood pH > 7.45 → overexcitability of the CNS

Question 4

What is acidosis and what does it result in?

Answer 4

systemic arterial blood pH < 7.35 → depression of the CNS

Question 5

How can the kidneys ↑ or ↓ pH of body fluids?

Answer 5

• Proximal convoluted tubules Sodium Hyrdogen Antiporters secrete Hydrogen, reabsorb Sodium
• Collecting ducts intercalated cells reabsorb Potassium and Bicarb and secrete Hydrogen.

Question 6

How does the respiratory system affect the acid-base balance?

Answer 6

As we exhale CO2, we reduce the amount of hdrogen ions in our system and therefore cause pH to rise

Question 7

What are the 3 major chemical buffer systems and what do they do?

Answer 7

Maintain Ph which is really important inbthe maintenance of homeostasis:
1. Bicarbonate (ESF?)
1. Phosphate
1. Protein
Allow for Hydrogen ions to be retained or secreted therefore changing pH. ST system

Question 8

What does ADH do?

Answer 8

Increases permeability of kidney cells, therefore reabsorbing more water back into the system (facilitative not obligatory)

Question 9

What do ions do?

Answer 9

Ions formed when electrolytes dissolve in fluids control
* Osmosis of water b/w compartments
* Help maintain acid-base balance
* Carry electrical current

Question 10

Classify 3 water balance disorders

Answer 10

Dehydration or hypernatraemia - execessive water loss or water and ions. Can occur through consumption of diuretics
Hyponatraemia - excessive water intake

Question 11

Describe factors that determine fluid shifts.

Answer 11

Most often as a → of △ in concen. of Na+, △ in osmolarity of interstitial fluid → in fluid imbalances. ↑ in osmolarity of interstitial fluid draws water out of cells and they shrink slightly

Question 12

What is the volume of fluid compared to solids in the compartments of the body and what are they composed of? t

Answer 12

55% F - 60% Male
2/3 ICF
1/3 ECT of which 80% interstitial fluid, 20% plasma

Question 13

What are the 5 things, 4 hormonal, that affect whether water is ingested, maintained or excreted?

Answer 13

Thirst ctr hypothalamus stimulates desire to drink
Angiotensin II - stimulate secretion of aldosterone ↓ → ↓loss of water in urine
Aldosterone promotes water reabsorption of Na+ & Cl- ↓ ↑ water reabsorption via osmosis → ↓ loss of water in urine
ADH - promotes insertion of water channel proteins into apical membranes of principal cells in collecting ducts of kidneys ↑ water permeability of these cells and therefore water reabsorption ↓ loss of water in urine
Atrial natriuretic peptide promotes natriuresis - elevated urinary excretion of Na+ & Cl- accompanised by water (obligatory?) → ↑ loss of water in urine

Question 14

What three mechanisms regulate the body’s ph?

Answer 14

1. Chemical buffers - can increase or decrease amount of hydrogen ions retained or secreted
2. Respiratory system - incresaed exhalation results in increased exhalation of hydrogen ions and therefore increase in pH
3. Renal system - long term maintenance of pH