Physiology 1

Question 1

what is osmolarity

Answer 1

the concentration of osmotically active particles present in a solution

Question 2

how do you calculate osmolarity in the body

Answer 2

concentration of a solution x the number of osmotically active particles present

Question 3

what is the osmolarity of body fluids

Answer 3

300mosmol/l

Question 4

what is tonicity

Answer 4

the effect a solution has on cell volume

Question 5

what is an isotonic solution

Answer 5

one that causes no change in cell volume

Question 6

what is a hypotonic solution

Answer 6

one that causes an increase in cell volume

Water moved from the solution into the cell

Question 7

what is a hypertonic solution

Answer 7

one that causes a decrease in cell volume

(cell looses fluid by osmosis from inside to outside cell0

Question 8

what is a fluid with an osmolarity <300

Answer 8

hypotonic

has less osmotically active particles in it than inside the cell so water moves into the cell

Question 9

what is a fluid with osmolarity >300

Answer 9

hypertonic

more osmotically active particles are outside the cell than in so water leaves the cell via osmosis

Question 10

why is the permeability of the cell membrane important in osmosis

Answer 10

because some cell membranes favour one solution over another

eg. urea and sucrose both have an osmolarity of 300 (so should be isotonic) however sucrose is isotonic and urea is hypotonic

this is because RBC membranes are v permeable for urea but not as much for glucose

Question 11

what are the 2 main body compartments which hold water

Answer 11

intracellular fluid (2/3)

extracellular fluid (1/3)

Question 12

what is the extracellular fluid made up of

Answer 12

interstitial fluid (80%)
plasma (20%)
lymph + trans cellular fluid (CSF,pleural) (negligible)

Question 13

how do you measure the volume of fluid in a specific compartment

Answer 13

tracers

measure the distributed volume of a specific tracer in a body compartment

Question 14

what tracer measures plasma volume

Answer 14

labelled albumin

Question 15

what tracer measures total body water

Answer 15

3H3O

Question 16

what fluid outputs does the body have no control over (insensible)

Answer 16

skin - diffusion of water across skin surface area

lungs - see it on cold day when you breath out vapour

Question 17

what fluid outputs does the body control (sensible loss)

Answer 17

sweat
urine
faeces

eg. if dehydrated you can reduce amount of urine produced and if over hydrated you increase the amount of urine produced

Question 18

what are the fluid inputs to the body

Answer 18

fluid intake
food intake
metabolism

Question 19

how is water imbalance manifested (differences between water input and output)

Answer 19

osmolarity

Question 20

why do you still produce urine (a concentrated urine) when you are v dehydrated

Answer 20

some metabolites being excreted need to be excreted in fluid

Question 21

what ions are most abundant in the intercellular fluid

Answer 21

K+

Question 22

what ions are most abundant in the extracellular fluid

Answer 22

Na+
CL_
HCO3-

(like the sea)

Question 23

osmolarity of ECF and ICF are the same true/false

Answer 23

TRUE

if there are changes in salt conc in extracellular fluid it changes osmolarity causes water to move to try and restore the change - balances out

Question 24

what are fluid shifts

Answer 24

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

maintain homeostasis

Question 25

what are some challenges to homeostasis

Answer 25

gain or loss of water
gain or loss of NaCl
gain or loss of isotonic fluid (bc it changes ECF volume)

Question 26

when does electrolyte balance occur

Answer 26

when rates of electrolyte gain = loss

Question 27

do electrolyte concentration affect water balance?

Answer 27

YES

via changes in osmolarity

Question 28

what are the two major contributors to the osmotic concentrations of ECF and ICF (electrolytes)

Answer 28

K+

Na+

Question 29

what is the relationship between sodium and water

Answer 29

WATER FOLLOWS SALT

Question 30

Why is it so vital to regulate Na

Answer 30

it is mainly present in the ECF so is a MAJOR determinant of ECF volume and therefore blood volume/pressure

Question 31

where is 95% of the body’s k+

Answer 31

In the cells (intracellular fluid)

Question 32

what can happen if there are small leakages or increased uptake of potassium into cell/out of cells

Answer 32

muscle weakness- paralysis

cardiac irregularities