Ch 14. Final Osmoregulatory Organs (Book) Flashcards
apical surface of an epithelial cell
continuous with the external world (ex. sea, gut lumen, kidney tubule lumen)
aka. mucosal or laminal surface
basal surface
faces an internal compartment with extracellular fluid
aka. serosal surface
Na/K ATPase
3 Na+ out
2 K+ in
maintain -70mV, uses ATP
basolateral surface…type of P-ATPase
3 classes of ion-motive ATPase pumps
F-ATP synthase
V-ATPase
P-ATPase
F-ATP synthase
drive ATP synthesis in mitochondria
V-ATPase
vacuolar type
hydrolyze ATP to make an electrochemical gradient
P-ATPase
include Na/K
Ca pump of muscle contraction
H+/K+ pump in the stomach
net movement of chloride across the cell membrane generates a ______________ membrane potential that can…
transepithelial
move sodium against its gradient paracellularly (btw cells)
can Na/K and proton ATPases be modified by hormones?
yes
ex. both increased activity by aldosterone
kidney anatomy
outer cortex and inner medulla
renal pelvis turns into the ureter –> bladder
urine contains water and other by-products of _________, like…
metabolism
urea, NaCl, KCl, phosphates
the function of the kidneys is to maintain…
more or less constant body composition
ex. composition of urine reflects water taken in and composition of food ingested
actual volume of urine produced is made of…
water ingested plus water made through metabolism
minus evaporative water loss and sweating and pooping
how is sensation of fullness via bladder produced
as bladder is stretched by filling, stretch receptors in the wall generate nerve impulses carried by sensory neurons
functional unit of the kidney is the ______ which empty into the __________ _____
nephron, collecting ducts
nephron structure
long tube structure closed and widened at the beginning (Bowman’s capsule) and opened at the distal end –> collecting duct
bowman’s capsule
contains a cluster of capillaries called the glomerulus where urine formation begins
3 regions of a nephron
proximal nephron
loop of Henle
distal nephron
proximal nephron
contains Bowman’s capsule and proximal tubule
loop of Henle structure
has a descending limb and ascending limb
distal nephron
a distal tubule that enters into a collecting duct
two types of nephron
juxtamedullary
cortical
juxtamedullary nephron
has glomeruli in the inner cortex
long loops of Henle plunge far into the medulla
cortical nephrons
glomeruli in the outer cortex
short loops of Henle that extend a short distance into the medulla
without a loop of Henle you can’t make
concentrated urine
path of blood from renal artery
renal artery –> afferent arteriole –> glomerular capillaries of bowman’s capsule –> efferent arteriole –> vasa recta around loops of Henle
3 main processes that contribute to urine composition
filtering blood plasma into an ultrafiltrate in the lumen of Bowman’s capsule
tubular reabsorption of 99% of water and salts form ultrafiltrate (leaves behind waste products like urea)
tubular secretion of substances via active transport
what does glomerular filtrate contain
all parts of blood except RBC
nearly all blood proteins
the process of ultrafiltration in the glomerulus depends on what
net pressure gradient (passive)
from hydrostatic pressure difference across 2 compartments
and colloid osmotic pressure
fenestrated capillaries in glomerulus
pores that are 100x more permeable than normal ones
pedicles extending from podocytes have filtration slits between them
help glomerular filtration
to ensure that changes in bp and co have little effect on normally high glomerular filtration rate…
many regulatory processes involving paracrine and endocrine secretions and neuronal control
how does an increase in bp affect glomerular filtration rate
not much
afferent arteriole constricts so increased pressure isn’t transmitted
what can specialized cells of the juxtaglomerular apparatus do to help modulate renal blood flow
special distal-tubule cells (macula densa) monitor osmolarity and flow
modified-smc called granular cells in the afferent arteriole secrete renin, which affects bp
macula densa cells release..
paracrine substances that cause vasoconstriction or vasodilation
neuronal control
sympathetic activation causes vasoconstriction of afferent arteriole and less glomerular filtration – when bp drops sharply
can sympathetic activation cause contractions of cells in the glomerulus?
yes… reduces area available for filtration
renin release causes what
increased angiotensin II in the blood
causes arteriole constriction to raise bp and increase rate of filtration
stim release of aldosterone and vasopressin to promote tubular reabsorption of salts and water
renal clearance of a substance
measure of how much it is reabsorbed or secreted
micropuncture technique to discover how urine moves through the nephron
micropipette inserted and oil injected until proximal tubule
perfusion fluid injected in oil column to force a droplet the the end of the tubule
after 20 min, 2nd fluid forces a second oil droplet forward and perfusion fluid is collected
tubule ability to reabsorb is determined by comparing perfusate composition b4 and after
the proximal tubule begins the process of concentrating _________ filtrate, is the most important tubule segment in the active reabsorption of _______
glomerular, salts (70% and a nearly proportional amount of water and other solutes like Cl-)
in the proximal tubule, _____ is the major solute reabsorbed proximally, and ______ is the major solute reabsorbed distally
NaHCO3, NaCl
brush border in proximal tubule
tons of microvilli to increase absorptive surface area of apical membrane
do the descending limb and ascending limb of the loop of Henle exhibit active salt transport?
no, fairly impermeable to NaCl and urea, but permeable to water (descending limb only)
opposite for ascending limb
thick medullary ascending limb of loop of Henle
actively transports NaCl our to the interstitial space
low water permeability
collecting duct highly water permeable
moves from dilute urine in the duct to the concentrated interstitial fluid
final concentration of urine
controllable by ADH
aldosterone
steroid hormone that causes an increase in sodium reabsorption
3 proposed methods of sodium reabsorption
Na/K pump activity increases
ATP production increases to power Na/K pump
premeability of membrane to Na increases
ADH
increases water permeability of distal tubule and collecting duct to promote water reabsorption
uses cAMP amplification to insert more aquaporins in apical memb of collecting duct
atrial natriuretic peptide (ANP)
released by atrial heart cells to promote urine production and sodium excretion
renin-angiotensin system
renin cleaves angiotensinogen into angiotensin I and angiotensin converting enzyme (ACE) turns angiotensin I into angiotensin II which stimulates secretion of aldosterone and ADH
tubular secretion occurs from where to where
plasma into tubular lumen
substances that may be secreted across proximal tubule
K+, H+, NH3
molecules get conjugated to move them across
most K+ ions filtered at the glomerulus are reabsorbed from filtrate in the proximal tubule and loop of Henle because of what transporters
Na/2Cl/K cotransporter in apical memb
Na/K pump in basolateral memb
can the distal tubule and collecting duct secrete K into the lumen
yes, balances reabsorption
Basolat - Na/K pump brings K from blood into cell
Apical - Na moves into cell through channels, K moves into urine by channels (both passive down gradients)
aldosterone leads up enhanced __ uptake and __ excretion
Na, K
2 factors of pH control in mammals
acid excretion by kidneys
CO2 excretion by lungs
during which part of the tubule is acid added to urine
entire length
urine becomes progressively more acidic
in proximal tubule and loop of Henle how are protons secreted
Na/H antiporter
A cells are found in the
distal tubule and collecting duct
what do A cells do
Secrete acid into urine
Carbonic anhydrase converts CO2 –> H+ + HCO3-
Apical - H+ ATPase moves H+ into urine, Na reabsorbed
Basolat - Na/K pump moves Na into blood, and HCO3-/Cl- antiport moves HCO3 into blood and Cl into cell
B cells are found in the
distal tubule and collecting duct
what do B cells do
Secretes HCO3- into urine in exchange for Cl
carbonic anhydrase
Apical - HCO3-/Cl- antiport moves Cl into cell and HCO3- into urine
Basolat - H+ ATPase pumps H+ into blood, and Cl- channels move Cl into blood
does acidosis increase the activity of A cells
yes
does alkalosis increase the activity of B cells
yes
what changes happen in A cells in acidosis
activity of Na/K ATPase and bicarb-chloride exchangers
proton secretion by renal tubular cells ______ the pH of the ultrafiltrate, which ______ the gradient against which protons are transported
decreases, increases
this is why the ultrafiltrate is buffered by bicarb, phosphate, etc
long term mechanism for correcting acidosis
producing ammonia ions that form ammonium ions after picking up H+ and secreting
concentrating urine is directly proportional to
loop of Henle length
because there is osmotic removal of water in the collecting duct
why is there increase in osmolarity of fluid from descending limb of loop of henle to hairpin turn
permeable to water but not nacl so water moves out
what happens as fluid moves up ascending limb of loop of henle
NaCl is actively moved out and some diffuses out
causes even more water to flow out
when is urea removed
when collecting duct enters deep inner medulla
flows out of tube and causes more water to flow out too
osmolarity becomes progressively ________ as you go deeper into the medulla
higher
countercurrent system with vasa recta
as blood enters inner medulla it picks up a lot of solute and releases water
when it moves to cortex is releases solute
when is ADH stimulated for release
dehydration (inc in osmolarity) –> hypothalamic neurosecretory cells impulses –> neurosecretory terminals in pituitary –> ADH
blood loss –> reduce inhibitory effect of receptors –> ADH
overall pathway
formation of urine begins w/ concentration of glomerular filtrate into hyperosmotic fluid in proximal tubule
75% salt and water removed through proximal tubule
in loop of Henle there is little net change of osmolarity, but a countercurrent multiplier sets up a concentration gradient
gradient drives osmotic reabsorption of water and resultant concentrated urine
proximal tubule and loop of Henle transporters for Na reabsorption
Na passively crosses apical memb via Na/2Cl/K and gluc/Na cotransporters
Na/K pump in basolat moves Na into blood (reabsorbs)
K and Cl into blood down their conc gradients through ion channels
Proximal tubule reabsorption of ultrafiltrate transporters
Apical - Na/glu cotransporter brings them into cell & Na/2Cl/K into cell
Basolat - Na/K pump moves Na into blood & K and Cl channels move them into blood
Proximal tubule secretion
CO2 into cell –> H+ + HCO3- by carbonic anhydrase
Apical - H+/Na antiport moves H+ into urine and Na into cell
Basolat - Na/K pump moves Na into blood & K and HCO3- move into the blood by channels
