Exam 1 Ch6: Extracellular Environment Flashcards
Extracellular environment
a. Includes all constituents of body outside cells
cells receive nutrients from and get rid of waste over
plasma membranes from and to extracellular fluid
67% of total body H20 is
inside cells
- intracellular compartment
33% of total body H20 is outside cells
= extracellular compartment-ECF
ECF
Extracellular compartment fluid
20% of ECF
blood plasma contained in blood vessels
80% of ECF
interstitial fluid = tissue fluid contained in gel-like matrix
Cells of our body are surrounded by
extracellular matrix
Extracellular matrix
a meshwork of protein fibers (collagen & elastin fibers) linked to molecules of gel-like ground substance
interstitial fluid
tissue fluid resides in hydrated gel of ground substance
interstitial fluid also contains
glycoproteins, proteoglycans, which form chemical bonds between carbohydrates on the surface of cells and protein fibers
Plasma membrane
Separates intracellular environment from extracellular environment
significance of plasma membrane to nutrients
all nutrients reaching cell and all waste leaving the cell must pass over plasma membrane
plasma membrane allows only certain kinds of molecules to pass
selective permeable
plasma membranes are impermeable to
proteins, nucleic acids, some ions, and/or other molecules necessary for cellular function/metabolism
Categorization of transport into and out of cells:
- carrier - mediated transport
2. Non-carrier mediated transport
carrier - mediated transport
involves specific protein transporters
Facilitated diffusion and Active transport
non- carrier mediated transport
occurs by diffusion through membranes
Categorization of transport into and out of cells according to energy requirements
- passive transport
- active transport
passive transport
moves compounds down concentration gradient (from areas of ↑ concentration to areas of ↓ concentration)
does passive transport requires energy?
No
Passive transport includes
simple diffusion
what are simple diffusion
osmosis and facilitated diffusion
Active transport
moves compounds up a concentration gradient (from areas of ↓ concentration to areas of ↑ concentration)
active transport requires
energy & specific transporters
Diffusion
random motion of molecules (due to heat energy); the net movement is from region of high to low concentration
in diffusion what kind of compounds readily diffuse thru cell membranes
non-polar
hyrophobic
- also some small, polar, but uncharged molecules including C02 & H20
Diffusion of H2O is called
osmosis
in diffusion cell membrane is impermeable to
charged and most polar compounds
through diffusion charged moleculels must have what to move across membrane
ion channel or transporter
rate of diffusion depends on
- Magnitude of its concentration gradient, which creates driving force (DF)
- Permeability of membrane to it
- Temperature
- Surface area of membrane
ions such as what require protein channels to permeate the membrane
K+ and Na+
Osmosis
net diffusion of H20 (universal solvent) across a selectively permeable membrane
In Osmosis H2O
H20 diffuses down its concentration gradient
H20 is less concentrated where there are more solutes
In Osmosis solutes has to be Osmotically active
cannot freely move across membrane for osmosis to cccur
dilute solutions
more H20 (solvent), less solute
Concentrated solutions
contain less H20 (solvent), more solute
H20 diffuses down its concentration gradient until
its concentration is equal on both sides of membrane, thus there is a change in volume
Some cells have water channels (aquaporins) to
facilitate osmosis in special membranes (ex. kidney cells)
osmotic pressure
measure of the tendency for a soln. to gain H2O by osmosis
Osmotic pressure is proportional to
solute concentration
greater solute concentration = greater osmotic pressure
force that would have to be exerted to stop osmosis
Indicates how strongly H20 wants to diffuse
Tonicity
effect of a solution (sln) on osmotic movement of H20
Isotonic
slns have same osmotic pressure;
has an equal concentration of solute (solid);
no osmosis
hypertonic
slns have higher osmotic pressure & are osmotically active; has a higher concentration of solute (solid)
hypotonic
solns have lower osmotic pressure; has a lower concentration of solute (solid)
Molar
pertaining to the number of moles of solute per liter of solution
Molal
pertaining to the number of moles of solute per kilogram of solvent
Osmolality
measure of the total concentration of a solution; the # of moles of solute per kilogram of solvent
Osmolarity
measure of the total concentration of a solution; the # of moles of solute per liter of solution
Mole
number of grams of a chemical that is equal to its formula weight ex: H2O mw = 18
Blood osmolality maintained in
narrow range around 300 mOsm
if dehydrated osmoreceptors in hypothalamus stimulate:
ADH antidiuretic hormone release
Which causes kidney to conserve H20 by stimulating insertion of aquaporins into kidney membranes
& thirst
Molecules too large & polar to diffuse are transported across membrane by
protein carriers embedded in plasma membranes
Protein carriers exhibit
Specificity for single molecule
Competition among substrates for transport that are very similar
Saturation when all carriers are occupied
saturation are called
Tm (transport maximum)
facilitated diffusion
passive transport = no energy required
down concentration gradient = from higher to lower concentration
by carrier proteins (embedded in membranes)
examples of carrier proteins
. Glucose transporters (GLUT4 in skeletal muscle) that reside in membrane bound vesicles within the cytoplasm until stimulated by insulin to be inserted into the plasma membrane
Primary active transport
transport of molecules against a concentration gradient;
Requires ATP
Primary active transport:
requires ATP
Molecule or ion binds to recognition site on carrier protein -> hydrolysis of ATP -> phosphorylation of carrier protein -> conformational change -> release of molecule/ion to opposite side
Membrane Transport Systems: Primary Active Transport: Na+/K+ Pump
uses
ATP to move 3 Na+ out & 2 K+ in against their gradients; between 200 – several million/cell!!!
Steep Na+ gradient
drives coupled transport;
adjusting the pump activity helps regulate resting (basal) metabolic rate;
Na+ and K+ concentrations are used by muscle and nerve cells to conduct electrical impulses;
osmoregulation
Secondary Active Transport (Coupled Transport)
Uses energy from “downhill” transport of Na+ to drive “uphill” movement of another molecule
ATP required to maintain Na+ gradient via
Na+/K+ ATP-ase, BUT IS NOT USED DIRECTLY!v
Cotransport (symport)
secondary transport in same direction as Na+ (ex. glucose)
Countertransport (antiport)
moves molecule in opposite direction of Na+ (ex. Ca2+)
epipthelial membranes
cover all body surfaces and line the cavities of all hollow organs
- Molecules/ions must pass through these epithelial membranes
absorption
transport of digestion products across intestinal epithelium into blood
reabsorption
transports molecules out of urinary filtrate back into blood
transcellular transport
moves material through the cytoplasm of epithelial cells
paracellular transport
moves material through tiny spaces between epithelial cells
Bulk transport
Is way cells move large molecules/particles across plasma membrane
Bulk transport occurs by
endocytosis (into cells) & exocytosis (out of cells) via the fusion of membrane bound vesicles
Recall: H2O distribution
Intracellular
exgtracellular
intracellular H2O distribution
(~ 67%) = 2/3 of body H2O is inside cells (~27 – 30 L H2O)
extracellular H2O distribution
(~ 33%) = 1/3 total body H2O is outside of cells (~14 – 16.5 L H2O)
( Interstitial and Blood)
Interstitial (tissue fluid)
(80% ECF) = 11 – 13 L H2O
blood
(20% ECF) = 3 – 3.5 L H2O
Nutrients and waste must be exchanged via
fluid in capillaries (blood) and the fluid in tissues (extracellular fluid)
Distribution of ECF between blood & interstitial compartments is in state of
dynamic equilibrium
dynamic equilibrium
continuously circulating, formed from, and returned to the vascular system
There are forces at work controlling this movement
Fluid movement into/out of capillaries depends on
Net filtration pressure
Net filtration pressure
hydrostatic pressure in capillaries (17-37 mm Hg) – hydrostatic pressure in ECF (1 mm Hg)
Hydrostatic pressure is exerted by
fluid
hydrostatic pressure
~ 37 mm Hg at arteriolar end of systemic capillaries and ~17 mm Hg at the venular and of capillaries
Oncotic pressure
Colloid osmotic pressure in capillaries (25 mm Hg) - Colloid osmotic pressure in tissue fluid (0 mm Hg)
Colloid Osmotic pressure
osmotic pressure exerted by proteins in fluid
Overall Fluid Movement into and out of Capillaries
The 2 factors
net filtration
oncotic pressure
net filtration is determined by
hydrostatic pressure (HP)
Oncotic pressure is determined by
determined by colloid osmotic pressure (COP)
**At the arteriole end of capillary bed, HP is highest inside….What happens?
Close to the arterial end of the capillary, it is approximately 10 mm Hg, because the CHP of 35 mm Hg minus the BCOP of 25 mm Hg equals 10 mm Hg. Recall that the hydrostatic and osmotic pressures of the interstitial fluid are essentially negligible. Thus, the NFP of 10 mm Hg drives a net movement of fluid out of the capillary at the arterial end
At the venule end of the capillary bed, COP is the highest inside, what happens?
At approximately the middle of the capillary, the CHP is about the same as the BCOP of 25 mm Hg, so the NFP drops to zero. At this point, there is no net change of volume: Fluid moves out of the capillary at the same rate as it moves into the capillary. Near the venous end of the capillary, the CHP has dwindled to about 18 mm Hg due to loss of fluid. Because the BCOP remains steady at 25 mm Hg, water is drawn into the capillary, that is, reabsorption occurs. Another way of expressing this is to say that at the venous end of the capillary, there is an NFP of −7 mm Hg.
85% of fluid filtered from capillaries is returned directly to
capillaries
5% of fluid filtered from capillaries is returned to
circulation via lymphatic system
Edema
excessive accumulation of tissue fluid
What maintains proper ECF levels
Normally filtration, osmotic reuptake, & lymphatic drainage
edema can result from
- High arterial blood pressure
- Venous obstruction
- leakage of plasma proteins into ECF
- Myxedema
- Decreased plasma protein levels
- Obstrucgtion of lyphatic drainage
high arterial blood pressure
↑ capillary pressure excessive filtration
Venous obstruction produces
congestive ↑ in capillary pressure
leakage of plasma proteins into ECF causes
↓ in osmotic flow into capillaries
Myxedema
excess production of glycoproteins (mucin) in extracellular matrix from hypothyroidism
Decreased plasma protein levels results from
liver or kidney disease
obstruction of lymphatic drainage caused by
elephantiasis (filariasis = parasitic nematode)
