Body fluid compartments Flashcards
total body water as a percentage of body weight
50-70%
correlation: body water and body fat
inverse correlation
females have a higher percentage of adipose tissue than males so have less body water
where is total body weight distributed
between 2 major compartments
intracellular
extracellular
intracellular fluid
contained within the cells
2/3 of the total body water
extracellular fluid
outside the cells
1/3 of total body water
divided into plasma and interstitial fluid
divisions of extracellular fluid
1/4 plasma
3/4 interstitial fluid
plasma
fluid circulating in the blood vessels
interstitial fluid
fluid that bathes the cells
rule to remember the divisions of fluid compartments
60-40-20
60= water
40= ICF
20= ECF
components of ICF
potassium and magnesium are major cations
proteins, organic phosphates (ATP, ADP and AMP) are major anions
ECF components
major cation is sodium
major anions is chloride and bicarbonate
plasma components
55% blood volume
of which 93% is water and 7% is proteins q
interstitial fluid components
ultra filtrate of plasma
has nearly the same composition as plasma except plasma proteins and blood cells
what is the barrier between plasma and interstitial fluid
capillary wall
nature of the capillary wall
one layer of cells
pores between cells
water: freely permeable
small molecules, permeable
large molecules e.g. albumin, impermeable
what is the barrier between ECF and ICF
cell membrane
nature of the cell membrane
lipid bilayer
channels and carriers
freely permeable to water
relatively impermeable to ions
relatively impermeable to large molecules
lipid bilayer
repels water and anything dissolved n it
channels and carriers
membrane proteins that allow charged ions and water to cross
how do ions cross the cell membrane
via channels
very slowly
very small amounts
equivalent
used to describe the amount of charged solute
number of moles of the solute multiplied by its valence
osmole
number of particles in which a solute dissociates in solution
osmolarity
concentration of particles in solution expressed as osmoles per litre
what does it mean if a solute doesn’t dissolve in solution
then its osmolarity is equal to its molarity
if solute dissolves into more than one particle in solution then what Does that mean
then osmolarity is equal to molarity multiplied by number of particles in solution
osmolality
concentration os osmotically active particles
expressed as osmoses
per kilogram of water
principle of macroscopic electroneutrality
each compartment must have the same concentration of cations and anions
how to maintain concentration differences across cell membranes
sodium potassium pump
Calcium ATPase
why is maintaining a concentration different across membranes important
as the differences between ICF and ECF underlie important physiologic functions
important physiologic functions that rely on concentration differences in ICF and ECF
resting membrane potential of nerve and muscle
upstroke of the action potential of excitable cels
excitation-contraction coupling in muscle cells
absorption of essential nutrients
concentration differences between plasma and interstitial fluids
presence in proteins in the plasma compartment
plasma proteins do not cross the capillary walls because of their large molecular size
presence of albumin: A- in plasma
what are starling forces
pressures that control fluid movement across the capillary wall
oncotic and hydrostatic pressures
net movement of water out of capillaries
filtration
net movement into the capillaries
absorption
Pc
capillary hydrostatic pressure
fluid out of the capillaries
pi c
capillary oncotic pressure
fluid into the capillaries
Pi
interstitial hydrostatic pressure
fluid into the capillaries
pi i
interstitial oncotic pressure
fluid out of the capillaries
sigma
reflection coefficient
ranging between 0 and 1
describes with ease with which a solute crosses a membrane
Kf
filtration coefficient
net filtration equation
Kf[(Pc-Pi) - sigma(pi c - pi i)]
simple diffusion
passive transport
down concentration gradient
not carrier mediated
doesn’t use metabolic energy
isn’t dependent on Na+ gradient
facilitated diffusion
passive
down concentration gradient
is carrier mediated
doesn’t use metabolic energy
doesn’t depend on Na+ gradient
primary active transport
active
up concentration gradient
is carrier mediated
directly uses metabolic energy
isn’t dependent on Na+ gradient
cotransport
secondary active
is carrier mediated
indirectly uses metabolic energy
solutes move in the same direction as Na+ across the cell membrane
counter transport
secondary active
is carrier mediated
indirectly uses metabolic energy
solutes move in the opposite direction as Na+ across the cell membrane
secondary active
Na+ is transported down concentration gradient and one or more solutes are transported up
downhill
substances transported down an electrochemical gradient
uphill
substances transported against an electrochemical gradient
how does downhill transport occur
diffusion: simple or facilitated
requires no metabolic energy
how does uphill transport occur
active transport, either primary or secondary
requires metabolic energy
what do carrier mediated transport mechanisms have in common
need protein carrier
saturation
stereospecificity
competition
saturation
carrier proteins have a limited number of binding site for the solute
stereospecificity
binding sites for solute on the transport proteins are stereospecific
competition
although binding sites are specific they may recognise bind and even transport chemically related solutes
brownian motion
random dispersion of molecules from high to low concentration
diffusion occurs until it reaches what
same concentration on both sides
dynamic equilibrium
osmosis
flow of water across a semipermeable membrane because of differences in solute concentration
concentration differences of impermeant solutes establish osmotic pressure differences
osmotic pressure differences causes water to flow by osmosis
diffusion VS osmosis, diffusion points
can occur if both solute and solvent can pass through a permeable membrane
can occur in the absence of a permeable membrane
solute particles move form an area of higher concentration to an area of lower concentration
diffusion VS osmosis, osmosis points.
creates a pressure that can be measured
occurs when only solvent can pass through aa semi permeable membrane
solvent particles move across a semipermeable membrane from dilute to concentrated solution
example of facilitated diffusion
transport of D-glucose
into skeletal muscle
by GLUT4 transporter
example of primary active transport
sodium potassium pump
what maintains the Na+ gradient in secondary active transport
sodium potassium pump
examples of secondary active transport
cotransport/ symport
counter transport/ antiport
what happens if isotonic solution is added to ECF
osmolarity of ECF doesn’t change
main effect is an increase in ECF volume
what happens if hypertonic solution is added to ECF
osmolarity increases
causes osmosis of water out of the cells and into the ECF
almost all added NaCl remains in the ECF, fluid diffuses from cells into extracellular space, achieve osmotic equilibrium
net effect: increase in ECF volume, decrease in ICF volume, rise in osmolarity in both
what happens is hypotonic solution is added to the ECf
osmolarity of ECF decreases
some of the ECF water diffuses into the cells until the ICF and ECF have the same osmolarity
both ICF and ECF volumes are increased, ICF increases to a greater extent
