Physiology - Body Fluid Compartments and Challenges to Homeostasis

Question 1

What is osmolarity?

Answer 1

The concentration of osmotically active particles in solution

Question 2

How is osmolarity calculated?

Answer 2

Molar conc. x No. of osmotically active particles

(units osmol/l)

Question 3

Body fluids have an osmolarity of what value?

Answer 3

Around 300mosmol/l

Question 4

What is tonicity?

Answer 4

The effect a solution has on cell volume

Question 5

In terms of tonicity, what 3 things can a solution be?

Answer 5

Isotonic

Hypotonic (cell bursts)

Hypertonic (cell shrinks)

Question 6

What is the main difference between osmolarity and tonicity?

Answer 6

Tonicity takes into consideration the ability of solutes to cross the cell membrane

Question 7

What percentage of body weight is made up of water?

Answer 7

Males - 60%

Females - 50%

(Females have a higher average body fat percentage)

Question 8

What is the largest fluid compartment in the body?

Answer 8

Intracellular fluid

Question 9

How is the extracellular fluid split up?

Answer 9

Plasma

Interstitial fluid

Lymph and transcellular fluid (e.g. pleural fluid and CSF)

Question 10

What is the average input of fluid per day?

Answer 10

2500ml

(fluid intake- 1200ml, food intake - 1000ml, metabolism - 300ml)

Question 11

How can water be lost from the body?

Answer 11

Insensible (non alterable) loss from skin and lungs

Sensible (alterable) loss from sweat, faeces and urine

Question 12

In the extracellular fluid compartment, sodium and chloride ions are in ______ concentration and potassium is in ______ concentration

Answer 12

In the extracellular fluid compartment, sodium and chloride ions are in high concentration and potassium is in low concentration

Question 13

What is fluid shift?

Answer 13

Movement of water between fluid compartments in reponse to osmotic gradients

Question 14

In dehydration, the osmotic concentration of what increases?

Answer 14

ECF

Question 15

In which ways can fluid homeostasis be challenged?

Answer 15

Gain/loss of water

Gain/loss of salt

Gain/loss of isotonic solution

Question 16

Why is it important to regulate electrolyte balance?

Answer 16

1. Total electrolyte concentrations can directly affect water balance
2. The concentrations of individual electrolytes can affect cell function

Question 17

Why is it importnant to regulate potassium balance?

Answer 17

May cause:

Muscle weakness

Cardiac irregularities

(it affects membrane potential)

Question 18

What is the biggest output of salt from the body?

Answer 18

Urine

Question 19

In terms of the ECF, what are the kidneys responsible for?

Answer 19

Composition and volume