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Renal Week 1 2017/18 > 6: Physiology 1 > Flashcards

Flashcards in 6: Physiology 1 Deck (35)
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1

What is osmolarity?

Concentration of osmotically active particles (cause osmosis) in a solution

2

What is the unit of osmolarity?

Osmol / L

3

How do you calculate osmolarity?

You need:

molar concentration

no. of osmotically active particles

e.g 150mM NaCl

molar concentration = 150mM, 2 particles, 2x150 = 300 mosmol/l

or 100mM MgCl3 -> 100mM x 3 = 300 mosmol / l

4

What is the osmolarity of body fluid?

300 mosmol / L

5

What is the difference between osmolarity and osmolality?

Osmolarity measured in osmol/L

Osmolality measured in osmol/kg

pretty much the same

6

What is tonicity?

Effect a solution has on cell volume

7

What are

a) isotonic

b) hypotonic

c) hypertonic

solutions?

REFERS TO SOLUTE CONCENTRATION

a) If cell is ISOTONIC to solution, no change in cell volume

b) If cell is HYPOTONIC (i.e lower water content) to solution, INCREASE in cell volume > bursts

c) If cell is HYPERTONIC to solution, DECREASE in cell volume > shrinkage

 

8

Can solutions with the same osmolarity have different tonicities?

Why?

Cell membranes have different permeabilities

e.g Urea and sucrose are both isotonic to cell

Cell is very permeable to urea, water then follows urea causing lysis

compared to sucrose, which cell membrane is impermeable to, so no change in volume

9

Which sex has a greater body water content?

Why?

Males (60%)

Females have a greater fat content, which doesn't contain water

10

Which two compartments is body water held in?

Intracellular fluid (ICF)

Extracellular fluid (ECF):

ECF divided into plasma and interstitial fluid

11

Which body compartment has a greater volume?

Intracellular fluid (ICF)

12

Which compartment of the extracellular fluid has a greater volume?

Interstitial fluid

13

How can the volume of body compartments be measured?

Tracers

14

What is the equation for total body water content?

TBW = ECF ICF

15

To calculate volume of distribution:

add known mass of tracer to unknown volume of water

take known volume of water and calculate concentration of tracer

volume of distribution = mass / concentration

m

c v

16

What is the main input of water to the body?

Food and drink

17

What is the main output of water from the body?

Urine

18

On average, how much water is input and output every day?

2500 ml

19

What changes if there is a water imbalance in the body?

Osmolarity

20

Why can urine production never be turned off?

Toxic metabolites need to leave the body in solution i.e water

21

Which ions are found mainly

a) inside

b) outside the cell?

 

a) K+, Mg2negatively charged ions

b) Na+, Cl-

think cells swimming in salty water

22

What structures separate the

a) plasma from the interstitial fluid

b) the interstitial fluid from the intracellular fluid?

a) Capillary wall

b) Plasma membrane

23

What is fluid shift?

Movement of water between ICF and ECF by osmotic gradient

24

Osmolarity ___ as water leaves a compartment.

Water leaves More solute = INCREASED OSMOLARITY

Water enters > Less solute = DECREASED OSMOLARITY

25

What happens if the osmotic concentration of the ECF decreases?

Concentration of solute decreases (i.e water has entered ECF)

So osmotic gradient between high (ECF) and low (ICF)

So fluid shift to ICF

26

If osmotic concentration of the ECF increases, what happens?

Osmotic gradient from high (ICF) to low (ECF)

So fluid shift from ICF to ECF

27

As osmolarity increases there is a fluid shift (to / from) that compartment.

fluid shift TO that compartment

28

As osmolarity decreases there is a fluid shift (to / from) that compartment.

fluid shift FROM that compartment

29

Which organs regulate the composition and volume of the ECF?

Kidneys

30

How does the osmolarity of the ECF affect blood pressure?

If low, water moves to ICF, so plasma volume decreases, so BP decreases

If high, water moves to ECF, so plasma volume increases, so BP increases