intro to physiology - body fluids

Question 1

fluid balance

Answer 1

fluid intake and output are balanced (homeostasis can occur)

Question 2

fluid intake

Answer 2

water intake via drinking/eating, water enters blood and mixes in with rest of water stores

Question 3

fluid output

Answer 3

water output via kidneys, lungs, faeces, sweat, skin (not just as sweat)

Question 4

constituents of body fluids

Answer 4

electrolytes and non-electrolytes

Question 5

electrolytes

Answer 5

charged ions dissolved in water
-Na+
-K+
-Ca^2+
-Cl-
-proteins (colloids) negatively charged in solution

Question 6

non-electrolytes

Answer 6

uncharged
-glucose

Question 7

is blood a constituent of body fluid ?

Answer 7

no, blood cells do not dissolve so are not considered part of body fluid

Question 8

Na+

Answer 8

plasma: 142 mOsmol/L
interstitial: 139 mOsmol/L
intracellular: 14 mOsmol/L

Question 9

K+

Answer 9

plasma: 4.2 mOsmol/L
interstitial: 4.0 mOsmol/L
intracellular: 140 mOsmol/L

Question 10

Ca^2+

Answer 10

plasma: 1.3 mOsmol/L
interstitial: 1.2 mOsmol/L
intracellular: 0 mOsmol/L

Question 11

Cl-

Answer 11

plasma: 106 mOsmol/L
interstitial: 108 mOsmol/L
intracellular: 4 mOsmol/L

Question 12

protein

Answer 12

plasma: 1.2 mOsmol/L
interstitial: 0.2 mOsmol/L
intracellular: 4 mOsmol/L

Question 13

plasma and interstitial fluid values very similar

Answer 13

due to free movement

Question 14

interstitial fluid and intracellular fluid values very different

Answer 14

due to regulated movement

Question 15

despite different compositions, the osmolarity of intracellular and interstitial fluid is roughly the same (iso-osmotic)

Answer 15

therefore push/pull of water is balanced

Question 16

cations (+ve)

Answer 16

-Na+
-K+
-Mg^2+

Question 17

anions (-ve)

Answer 17

-Cl-
-HPO4^2-
-H2PO4^-
-HCO3^-
-protein

Question 18

within fluid compartment…

Answer 18

ionic charge balance is EQUAL, despite the no. of ions differing

Question 19

movement of substances within body fluids

Answer 19

-conc. gradients
-equilibrium
-passive transport
-active transport

Question 20

passive transport

Answer 20

-simple diffusion
-facilitated diffusion
-osmosis

Question 21

active transport

Answer 21

-Na+/K+ pump
-bulk transport

Question 22

diffusion

Answer 22

-chemical gradient: movement from high to low conc
-electrical gradient: movement from +ve to -ve charge or vice versa

Question 23

electrochemical gradient

Answer 23

balance between electrical and chemical gradients

Question 24

active transport

Answer 24

-transport of substances against conc. gradient
-requires energy in form of ATP
-specific carrier proteins

Question 25

Na+/K+ pump

Answer 25

-present on all cells -maintains unequal conc. of Na+ and K+ across the cell membrane -Na+ constantly pumped out in exchange for K+ to maintain electrical gradient across membrane -Na+ higher outside, K+ higher inside

Question 26

importance of Na+/K+ pump

Answer 26

-cells contain lots of solutes, causing water to move into the cell by osmosis, eventually bursting the cell -HOWEVER, this is prevented by use of the Na+/K+ pump -energy is used to pump 3 Na+ out and 2 K+ in, thus balancing the osmotic pressures -hence, at rest, Na+ conc. is higher outside and K+ is higher inside

Question 27

primary active transport

Answer 27

DIRECT use of ATP to transport against conc. gradient (e.g. Na+/K+ pump)

Question 28

secondary active transport

Answer 28

INDIRECT use of ATP to set up a gradient (e.g. Na+/glucose co-transporter

Question 29

Na+/glucose co-transporter

Answer 29

-low intracellular Na+ conc. is maintained by Na+/K+ pump -when Na+ enters the cell, it takes glucose inside with it, effectively AGAINST its conc. gradient -important in intestines and kidneys for glucose (re)absorption

Question 30

osmosis

Answer 30

net rate of diffusion of water across a semi-permeable membrane from a region of high water conc. to low water conc.

Question 31

when does osmosis occur ?

Answer 31

if the solute is too large to cross the membrane, water moves in order to adjust the conc. of the solute

Question 32

iso-osmotic

Answer 32

equal conc. of solutes so equal push-pull of water (ICF osmolarity = ECF osmolarity)

Question 33

osmotic pressure (π)

Answer 33

the amount of pressure required to stop movement of water

Question 34

Van't Hoff's law

Answer 34

π = CRT where: C= conc. of solutes (osmoles/L) R= molar gas constant (8.314 JK-1mol-1) T= absolute temp. (310K at normal body temp.)

Question 35

osmolarity

Answer 35

osmolar conc. of a solution is measure in osmoles (osmolarity)

Question 36

osmolarity for non-electrolytes (e.g. glucose)

Answer 36

osmolarity (osm/L) is EQUAL to the molarity (mol/L) -Mr of glucose = 180 -therefore, 180g glucose in 1L water gives a 1M (1mol/L) solution -which is therefore also a 1osm/L solution

Question 37

osmolarity for electrolytes (e.g. ions)

Answer 37

osmolarity (osm/L) is the molarity MULTIPLIED by the no. of ions in solution -1M (1mol/L) NaCL = 2 ions -therefore, 1osm/L x 2 = 2osm/L

Question 38

tonicity

Answer 38

-describes what happens to cells placed in solution -a measure of effective osmolarity -dependent on both osmolarity and whether solutes can enter/exit the cell

Question 39

iso-tonic

Answer 39

same osmolarity as plasma

Question 40

major contributors to ECF osmolarity

Answer 40

Na+ and Cl- ions

Question 41

major contributor to ICF osmolarity

Answer 41

K+ ions

Question 42

major difference between plasma and interstitial fluid (ISF)

Answer 42

protein levels are LOW in ISF

Question 43

plasma proteins create...

Answer 43

colloid osmotic pressure (oncotic pressure) so that the plasma (282) has a slightly higher osmolarity than ISF (281), plasma is HYPERtonic to ISF, thus pulling water INTO plasma (important in preventing loss of blood fluid vol.)

Question 44

HYPOtonic: conc. less than blood

Answer 44

used for dehydration (pushes water into cells)

Question 45

HYPERtonic: conc. more than blood

Answer 45

used for hyponatraemia (draws fluid into vascular compartment)

Question 46

ISOtonic: conc. most like blood

Answer 46

normal saline (0.9% NaCl), used after blood loss (expands blood vol.)