Phsyiology 1

Question 1

What is osmolarity

Answer 1

Concentration of osmotically active particles present in a solution

Question 2

What are the units of osmolarity

Answer 2

osmol/L or mosmol/L

Question 3

What 2 factors need to be known in order to calculate osmolarity

Answer 3

The molar concentration of the solution

The number of osmotically active particles present

Question 4

What is meant by osmotically active particles. Give 2 examples

Answer 4

NaCl has 2
MgCl2 has 3
Basically the number of elements in a solution

Question 5

300mM NaCl. Calculate the osmolarity

Answer 5

300x2 = 600mosmol/L

Question 6

What is the difference between osmolality and osmolarity

Answer 6

Osmolality - osmol/kg water
Osmolarity - osmol/L
They are interchangeable terms for weak salt solutions

Question 7

What is tonicity

Answer 7

the effect a solution has on cell volume

Question 8

Describe the movement of particles in an isotonic environment

Answer 8

No overall change in volume and no movement in one particular direction. Particles are still moving all the time

Question 9

Describe the movement of particles in an hypertonic environment

Answer 9

Water is lost from the cells into the environment and this results in a decrease in cell volume. Cell shrinkage

Question 10

Describe the movement of particles in an hypotonic environment

Answer 10

Water goes into the cells from the environment and this results in an increase in cell volume. Cell lysis

Question 11

What determines whether a solution will cause lysis etc.

Answer 11

the ability of the solutes to cross the membrane or not

Question 12

Why do females have lower total body water than males

Answer 12

Because they have a higher percentage of body fat which don’t contain a lot of water

Question 13

How much of a) the male body is water and b) the female body

Answer 13

a) 60%

b) 50%

Question 14

What are the 2 major compartments of total body weight

Answer 14

intracellular fluid (ICF) 
extracellular fluid (ECF)

Question 15

What separates the ICF and ECF

Answer 15

cell membrane

Question 16

What does the extracellular fluid include

Answer 16

Plasma
Interstitial fluid
Lymph and transcellular fluid

Question 17

Where is plasma found

Answer 17

Circulatory system

Question 18

What tracer can we use to obtain the distribution volume of TBW

Answer 18

3H2O

Question 19

What tracer can we use to obtain the distribution volume of ECF

Answer 19

Inulin

Question 20

What tracer can we use to obtain the distribution volume of Plasma

Answer 20

Labelled albumin

Question 21

How can we calculate ICF

Answer 21

TBW - ECF = ICF

Question 22

Describe the dilution principle to measure volume of distribution

Answer 22

Don’t know how much water is held in a container
Add a tracer at a specific dose (D = 42)
Mix them thoroughly and allow it to equilibrate with the water
Take a small sample (5ml) volume from the concentration and measure the concentration (C) of the sample
Use the formula below to calculate the initial volume
C = 0.005mg/5ml = 0.001mg/ml = 1mg/L
V= D/C = 42/1 = 42litres

Question 23

In what ways do we input water to the body

Answer 23

Fluid intake
Food intake
Metabolism

Question 24

In what way does water leave the body

Answer 24

Skin 
Lungs 
Sweat 
Faeces
Urine

Question 25

What is meant by insensible loss

Answer 25

we have no regulation over these losses

Question 26

What is meant by sensible loss

Answer 26

We have some physiological control over these losses

Question 27

What is water imbalance manifested as

Answer 27

changes in body fluid osmolarity

Question 28

Why do the kidneys never turn off urinary excretion

Answer 28

They get rid of metabolic waste products which are often only able to be excreted in solution

Question 29

What ions are in high concentration in ICF

Answer 29

K+

Question 30

What ions are in high concentrations in ECF

Answer 30

Na, Cl, HCO3

Question 31

What is the approximate values of ions in ICF

Answer 31

``` Na+ = 10 K+ = 140 Cl- = 7 HCO3- = 10 ```

Question 32

What is the approximate values of ions in ECF

Answer 32

``` Na+ = 140 K+ = 4.5 Cl- = 115 HCO3- = 28 ```

Question 33

What features allow the cells to maintain internal environments that differ in composition compared to their surroundings

Answer 33

The cell membrane | Membrane transport mechanism

Question 34

What are the main ions in the ICF

Answer 34

K Mg -vely charged proteins

Question 35

Why are the osmotic concentrations of both ECF and ICF identical

Answer 35

In part due to the kidneys

Question 36

What is fluid shift

Answer 36

The movement of water between the ICF and ECF in response to an osmotic gradient

Question 37

What would happen to a) the ECF and b) ICF and c) cell volume d) osmolality if the osmotic concentration of the ECF increased

Answer 37

a) ECF increases b) ICF decreases and cells become Hypertonic c) Cell volume decrease d) osmolality increases

Question 38

What would happen to a) the ECF and b) ICF and c) cell volume if the osmotic concentration of the ECF decreased

Answer 38

a) ECF decreases b) ICF increases and cells become Hypotonic c) Cell volume increases d) osmolality decreases

Question 39

If there is a gain of water, what happens to the ICF and ECF

Answer 39

They both increase

Question 40

If there is a loss of water, what happens to the ICF and ECF

Answer 40

They both decrease

Question 41

What happens to the ECF and ICF if NaCl increases

Answer 41

ECF increases but ICF decreases

Question 42

What happens to the ECF and ICF if NaCl decreases

Answer 42

ECF decreases but ICF increases

Question 43

Why is the regulation of ECF volume so important

Answer 43

For long term regulation of blood pressure

Question 44

Why is electrolyte balance important

Answer 44

Electrolyte concentrations can directly affect water balance (via changes in osmolarity) The concentrations of individual electrolytes can affect cell function

Question 45

Why are Na and K particularly important

Answer 45

They are major contributors to the osmotic concentrations of the ECF and ICF respectively They directly affect the functioning of all cells

Question 46

What is the major cation in the ECF

Answer 46

Sodium

Question 47

What is the major cation found within cells (ICF)

Answer 47

Potassium

Question 48

What is the major role of K+

Answer 48

establishing membrane potential

Question 49

What can disruption of K+ concentration result in

Answer 49

Muscle weakness --> paralysis | Cardiac irregularities --> cardiac arrest