fluid homeostasis

Question 1

What is the homeostasis set point for extracellular fluid concentration balance?

Answer 1

Set point of ECF fluid concentration: 280-300mOsmoles/L
Maintained by fluid balance

Question 2

How does fluid balance maintain homeostasis fo ECF concentration?

Answer 2

• Water in put: drinking, diet
• Water out put: urination, sweating, exhaling

Can be regulated
e.g.,
Dehydrated - thirst is stimulated
Over-hydrated - need to pee

Question 3

What is tonicity and how is it involved in fluid balance? What are the three types of tonicity in solution?

Answer 3

TONICITY: how solution will affect the water movement into and out of the cells
Hyper tonicity = cell placed in solution and loses water - shrinks
Isotonic = no net flow of water in/out and cell colume remains stable
Hypo tonicity = cell placed in solution and gains water - swells
Links to the loss/gain of water and electrolytes when ECF concentration is not maintained at set-point

Question 4

What is hypertonic dehydration ?

Answer 4

• water loss
• causes include fever, increased need to pee (polyuria), decreased water intake, end stage renal disease

Question 5

What is hypotonic dehydrate?

Answer 5

• electrolyte loss
• causes include Addisons, cystic fibrosis and Addisons disease

Question 6

What is isotonic dehydration?

Answer 6

• loss of both water and electrolytes
• symptoms include diarrhoea and excessive sweating

Question 7

How does lack of fluid balance maintenance lead to shock?

Answer 7

= certain level of blood pressure needs to be maintained in order to prefuse tissues with oxygen and remove co2 take it to lungs
= decrease in fluid balance - decrease in blood pressure - lack of oxygen in tissues - heart beats faster to try and compensate - can lead to shock

Question 8

How is fluid input and output equal?

Answer 8

Intake is 2.5L/day
- food and drink = food hydrolysed when microwaved and produces water vapour
- metabolism = cellular respiration which produces ATP as by-product (used in enzymatic reactions)
Output is 2.5L/day
- sweat
- lungs
- urine
- feces

Question 9

How is water stored within the body?

Answer 9

• storage within muscle
• involvement of storage/breakdown of macronutrients, i.e., storage of glycogen needs water in muscles, breakdown of glycogen releases water

Question 10

What are the typical body fluid stores?

Answer 10

• total body water is 42L
• interstitial fluid - 11L
• plasma - 3L
• intracellular fluid - 28L
• body composition varies based on diet, climate etc

Question 11

Which electrolytes are found within the fluid and what do they do?

Answer 11

1. Sodium = important for depolarisation and muscle contraction
2. HCO = act as buffer - to maintain pH
3. Proteins = sstay within cells because too large to cross lipid bilayers
4. Chloride = heart muscle and chloride shift

Question 12

What is the chloride shift?

Answer 12

• chlroide moves into ions and bicarbonate moves out
• helps maintain pH of blood

Question 13

How is pH of the blood maintained via bicarbonate ions?

Answer 13

• carbon dioxide mixes with water and forms carbonic acids
• excess amounts of acid in body decreases pH of blood
• carbonic anhydrase breaks down carbonic acids into hydrogen and bicarbonate ions
• bicarbonate ions pick up extra hydrogen

Question 14

How does the renal system work to maintain fluid homeostasis?

Answer 14

• kidneys -> water retention and warer loss

Question 15

How does vascular system help fluid homeostasis?