water balance

Question 1

why do we need h20

Answer 1

1) universal solvent
2) chemical reactions
3) major component of cells and plasma
4) lubricant of joints, organs

Question 2

what are 3 valuable features of water

Answer 2

1) high ability to absorb and retain heat
2) large amount of heat required to increase its temp
3) sweating carries a lot of heat away from the body

Question 3

how many litres of water does the average body contain and where is it distributed

Answer 3

32-40 litres
intracellular fluid - 25L
interstitial fluid - 12L
extracellular fluid - 3L

Question 4

what is the body made up of in terms of water, fat, protein, carbohydrates, minerals

Answer 4

water - 60%
fat - 18%
protein - 16%
minerals - 5.2%
carbohydrates - 0.7%

Question 5

define simple diffusion

Answer 5

movement from an area of high concentration to an area of low concentration through a semipermeable membrane - passive

Question 6

what factors effect diffusion - 5 things

Answer 6

1) temperature
2) molecular weight
3) steepness of concentration gradient
4) membrane surface
5) membrane permiability

Question 7

define osmosis

Answer 7

diffusion of water from high concentration to low concentration - passive

Question 8

what is a solution

Answer 8

a homogenous mixture of one or more dissimilar substances

usually a liquid (solvent) and a solute (electrolyte particle)

Question 9

what are the 3 types of solution

Answer 9

1) aqueous - small molecules dissolve
2) colloids - proteins or other large molecules
3) suspensions - even larger molecules

Question 10

define osmotic pressure and give an example

Answer 10

the force (thrust) of water movement into the higher concentration solution

or

the amount of hydrostatic pressure required to stop osmosis

e.g glucose can exert pressure by drawing water towards it

Question 11

how can you measure concentration of solutes

Answer 11

g/L weight per volume
%
moles per L (moles =number of molecules present in a sample)

Question 12

why moles

Answer 12

in physiology the number of molecules in solution is more important than % or weight

Question 13

define osmolarity, what does osmolality effect

Answer 13

number of osmoles/L solution
e.g 500 osmoles more concentrated than 300 osmoles

osmolality effects osmosis

Question 14

what does iso-osmotic mean, give an example

Answer 14

same osmolality

e.g concentration of electrolytes outside the cell is equal to that inside the cell - no movement - no change in shape of cell

Question 15

what is tonicity

Answer 15

ability of a solution to affect the cell - depends on concentration and permeability of the membrane to the solute

HYPOtonic - low
HYPERtomic - high

Question 16

describe what happens to a cell in a hypotonic solution

Answer 16

low concentration of solutes that do not cross the membrane - high water content - dilute

therefore cell would absorb water from outside and swell

Question 17

describe what happens to a cell in a hypertonic solution

Answer 17

high concentration of electrolytes outside the cell means low concentration of water

water moves to try and equal it out so cell would lose water and shrivel

Question 18

what do baroreceptors measure

Answer 18

pressure

Question 19

what do osmoreceptors measure

Answer 19

concentration

Question 20

what are the 4 treatments for dehydration

Answer 20

1) fluid therapy
2) Gelofusine - plasma expander (high osmotic pressure can draw liquid from interstitial fluid into cells - EMERGENCY
3) 5% glucose solution - isotonic
4) 0.9% saline - isotonic e.g post op fluid loss

Question 21

what factors influence water movement

Answer 21

hydrostatic pressure = the force exerted on the membrane by water/fluid

in a resting cell this will be stable as intracellular = interstitial

Question 22

water will always follow what?

Answer 22

solutes

Question 23

electrolytes move across plasma membrane by ? then water follows by ?

Answer 23

diffusion

osmosis

Question 24

what is the most dominant extracelluar ion and what is its normal range

Answer 24

Sodium (Na+)

around 0.5g / 135-145 mmol/L

Question 25

what is sodium needed for

Answer 25

nerve conduction (propagation of action potential)

Question 26

how is sodium controlled

Answer 26

ANP (increase) Aldosterone (lower)

Question 27

what is it called if someone has either too much sodium or too little
give 2 examples of what may have caused it
and 2 examples of symptoms for each

Answer 27

hypernatremic - high dietary intake, water loss (raised BP, convulsions)
hyponatremic - low dietary intake, burns (low BP, lethargy)

Question 28

what other ion apart from sodium (Na+) is involves in nerve conduction

how is it involved in nerve conduction

Answer 28

potassium (K+)

returning cell to its resting state after exitation

Question 29

what is the normal serum range of potassium (K+)

Answer 29

3.5 - 5.0 mmol/L

Question 30

what is it called if someone has either too much potassium or too little
give 2 examples of what may have caused it
and 2 examples of symptoms for each

Answer 30

hyperkalaemia - burns, kidney problem (muscle weakness, cardiac arrest)
hypokalaemia - use of diuretics, diarrhoea (slow HR, muscle weakness)

Question 31

how long can blood be stored

Answer 31

21-35 days

Question 32

what 3 things is calcium required for

Answer 32

health bones and teeth
muscle contraction
nerve excitability

Question 33

what are calcium levels controlled by

Answer 33

calcitonin (reduce)
parathyroid hormone (increase)

Question 34

what is it called if someone has either too much calcium or too little
give an example of what may have caused it
and 2 examples of symptoms for each

Answer 34

hypercalcaemia - excess hormone (fatigue, weakness)

hypocalcaemia - Vit D deficiency (muscle cramps)

Question 35

name 4 other electrolytes

Answer 35

1) magnesium
2) chloride
3) Bicarbonate
4) Phosphorus

Question 36

describe the structure of the cell membrane

Answer 36

phospholipid bilayer made up of proteins and carbohydrates with an oily film

Question 37

the membrane contains lipids and proteins

Answer 37

lipids (90% to 99%)

proteins (1 to 10%)

Question 38

what makes the membrane fluid

Answer 38

cholesterol

Question 39

what do membrane proteins function as - 5 things

Answer 39

call identity markers (antigens)
receptors 
channels, carriers and pumps 
cell-adhesion molecules
enzymes

Question 40

some protein channels are always open what does this allow through

Answer 40

water and hydrophilic solutes

Question 41

other channels are always closed and only open when… 3 things

Answer 41

1) chemical messengers bind to them
2) voltage changes across the membrane
3) mechanically stretched

Question 42

how do carriers function to transfer solutes across the membrane

Answer 42

bind to solutes and transfer them across

Question 43

what is it called if all carriers are full and being used

Answer 43

saturated

Question 44

carriers can be passive or active - give an example of each

Answer 44

passive (facilitated diffusion down concentration gradient) - glucose 
active energy (ATP) required as against concentration gradient - sodium-potassium pump

Question 45

what are the 2 main functions of the sodium potassium pump

Answer 45

(sodium out/potassium in)

regulates cell volume
maintains membrane potential