Fluids

Question 1

Do males or females have higher body water content? Why?

Answer 1

Males

Females have higher fat content and less skeletal muscle mass
- adipose tissue is least hydrated

Question 2

What are the fluid compartments in our body?

Answer 2

TOTAL = 40L, 60% body weight

2/3 intracellular: 25L, 40%
1/3 extracellular: 15L, 20%
- interstitial fluid (spaces between cells): 12L, 80% of ECF
- Plasma volume: 3L, 20% of ECF

Question 3

Differentiate between electrolytes and non electrolytes

Answer 3

Electrolytes
- inorganic salts, all acids and bases and some proteins
- conduct electricity
- have greater osmotic power

Nonelectrolytes
- glucose, lipids, creatinine, and urea
- do not conduct electricity

Question 4

Where is each electrolyte composition high? inside or outside cell?
Na+
K+
Ca2+
Mg2+
HCO3-
Cl-
HPO42-
SO42-
Proteins phospholipids cholesterol fats

Answer 4

Na+: OUT
K+: IN
Ca2+: OUT
Mg2+: signalling IN
HCO3-: buffer OUT
Cl-: OUT (negative charge inside cell)
HPO42-: IN (ATP)
SO42-: IN
Proteins phospholipids cholesterol fats:
- IN + blood plasma

Question 5

How much is water lost everyday?

Answer 5

2.5L

Question 6

What triggers the release of ADH?

Answer 6

• increase in plasma osmolality (more salt)
• trigger thirst

Question 7

How are hypothalamic osmoreceptors activated? (detect ECF osmolality to decrease) (4)

Answer 7

• increased plasma osmolality
• Dry mouth
• Dec BV or BP
• increased angiotensin II

Question 8

What does ADH promote? What does it target? (2)

Answer 8

1. Promotes water reabsorption in COLLECTING DUCTS of kidneys
2. Constricts arterioles, to inc BP

Question 9

What is the mechanism of dehydration?

Answer 9

1. Excessive loss of H2O from ECF
2. Inc of ECF osmotic pressure
3. Cells lose H2O to ECF by osmosis; cells shrink

Question 10

What is the mechanism of hypotonic hydration?

Answer 10

must be reversed quickly!
- renal insufficiency or a lot of water at once

1. Excessive H2O enters the ECF
2. ECF osmotic pressure falls
3. H2O moves into cells by osmosis; cell swells

Question 11

Define edema
What are the 2 causes?

Answer 11

Fluid accumulation in the interstitial space (tissue swelling)

1. increase flow of fluids out of the bloodstream
2. Hinders their return

Question 12

Explain 2 reasons of increased fluid filtration in edema

Answer 12

1. Increased capillary hydrostatic pressure
   - intensifies filtration at capillary beds
2. Increased capillary permeability
   - due to ongoing inflammation

Question 13

Explain what pressure reflects the hindering of fluid return in edema?

Answer 13

Decrease of colloid osmotic pressure (protein concentration)
- leaked proteins accumulate in interstitial fluid (between cells) drawing fluid from blood

Question 14

What does Na+ contribute in mOsm ECF

Answer 14

Contributes to 280 mOsm of 300 mOsm

Question 15

What role does aldosterone play in fluids? What does it target?

Answer 15

Target
- DCT and collecting duct

Role
- K+ secretion
- Na+ reabsorption

Question 16

What do each directly effect BV/BP?
Renin-angiotensin system
Neural regulation (baroreceptors)
Effects of ADH release

Answer 16

1. Both BV and BP
2. only inc BP
3. only inc BV

Question 17

When is Atrial natriuretic peptide released?
What is does it do?
What is the net result?

Answer 17

Released when: inc in BP and BV

Effects
- decrease in Renin –> angiotensin II –> vasodilation
- dec in ADH
- dec in Aldosterone
- overall decreases in Na

Result
- dec in BV and BP

Question 18

Where is most of filtered K+ absorbed?
What is released when there is an increase in K+ in the ECF

Answer 18

In PCT

Aldosterone is released to secrete K+

Question 19

Why is arterial pH higher than venous pH?

Answer 19

Venous pH carries CO2

Question 20

When does alkalosis and acidosis occur? pH?

Answer 20

Alkalosis
- too much HCO3- and H+
- allows pH to rise above 7.45

Acidosis
- too much CO2
- allows pH to drove below 7.35

Question 21

What is the 3 sequence of H+ regulation?

Answer 21

1. Chemical buffer systems
2. Respiratory center in brain stem
3. Renal mechanisms

Question 22

In chemical buffer systems explain where each buffer is important in.
Bicarbonate buffer
Phosphate buffer
Protein buffer

Answer 22

Bicarbonate buffer: ECF buffer
Phosphate buffer: ICF buffer + URINE
Protein buffer: ICF + plasma

Question 23

What is the equation for respiratory buffer systems?

Answer 23

CO2 + H2O <–> H2CO3 <–> HCO3- + H+

Question 24

What are the 2 ways in regulating acid-base balance? Where do they occur? Which ones are acidosis or alkalosis?

Answer 24

1. Reabsorbing NaHCO3 or generating new NaHCO3
   - In PCT cells and type A intercalated cells
   - Acidosis
2. Excreting NaHCO3
   - in PCT cells and type B intercalated cells
   - Alkalosis

Question 25

Explain the reabsorption of NaHCO3? Where does CO2 come from?

Answer 25

- for each H+ secreted, 1 Na + and 1 NaHCO3 are generated - CO2 from urine

Question 26

Explain the 2 ways for generating new NaHCO3? Where does CO2 come from?

Answer 26

1. Amount of H+ secreted into urine = amount of NaHCO3 generated by kidneys - CO2 from plasma 2. 1 glutamine -> 2 Ammonium ions (NH4+) + 2 NaHCO3 per metabolism

Question 27

Explain the secretion of NaHCO3

Answer 27

- Reverse of type A intercalated cells - NaHCO3 secretion - H+ reclaimed

Question 28

Explain Respiratory acidosis

Answer 28

High PCO2 - Person breathing shallow (too much CO2) High NaHCO3 - kidneys are retaining the bicarbonate and secreting H+

Question 29

Explain respiratory alkalosis

Answer 29

Low PCO2 - hyperventilation (too much O2) Low NaHCO3 - kidneys eliminate NaHCO3 and retain H+

Question 30

Explain metabolic acidosis

Answer 30

Low PCO2 - Deep breathing (more O2) Low NaHCO3 - Low pH

Question 31

Explain metabolic alkalosis

Answer 31

Normal PCO2 high HCO3 - high pH