Section 4 Flashcards
Avg plasma conc of Na+, Cl-, HcO3-, K+, Ca2+, and P:
140mM, 100mM, 24mM, 4mM, 2.5mM, 1mM
Osmolarity of blood:
300 mOsm
Fxns of kidney:
To REGULATE body fluid osmolality and V, electrolyte balance and acid balance, to EXCRETE wastes and foreign substances, and to PRODUCE and SECRETE hormones
How many liters do the kidneys filter per day?
180L
Daily urine output:
1.5L
Plasma V:
2L
% of plasma that enters the glomerular capillaries that is filtered into the nephrons:
15%
Blood supply to the renal tubules:
efferent arteriles
What are the renal tubules?
peritubular capillaries
The peritubular capillaries merge to form:
renal vein
What type of a filtrate enters Bowman’s space?
Protein-free plasma unltrafiltrate
What makes up the glomerulus?
Glomerular capillaries and mesangial cells
What are mesangial ells?
modified s.m. cells, regulatory roles
Components of renal corpuscle:
Glomerulus and Bowman’s Capsule
Components of juxtaglomerulus apparatus:
Mesangial cells of G, macula dense (ThickAL), and Renin secreting granular cell (afferent arteriole/ juxtaglomerular apparatus)
What cells secrete renin?
Granular cells of afferent arteriole
In which portion of the tubule system are the macula densa?
ThickAL
Solutes entering cells of macular dense from tubules:
Na, Cl, and K
Solutes moving in and out of cells of macula dense on side opposite tubule:
K in, Na and ATP out
ATP released from manual dense cells acts on:
ADO/A1 and ATP/P2X (of Granular and VSM cells) (check)
Too much fluid fluid through G and into Bowman’s space is controlled via signaling from:
cells of macula densa that sense high NaCl conc in the DT fluid
Where in tubule system are macula dense cells found?
ThickAL and DT? Or do the cell of the ThickAL sense the higher conc of NaCl in the adjacent DT?
What signals inhibit renin release?
Ca2+
Effects of inhibition of renin release:
constriction of afferent arterioles and decrease in GFR
Filtration barrier is formed by;
leaky endo cells of G caps, BM around endo cells, foot processes of podocytes
What type of barrier is the BM?
Charge-selective
What type of barrier is the filtration slit?
size-selective
GFR:
fluid flow across filtration barrier (V/t)
Often a first sign of kidney disease:
fall in GFR
How is GFR monitored?
blood/urine tests
What is used for the calculation of GFR?
clearance, also (V/t)
Clearance:
volume of blood that can be cleared of a substance/ t
T or F? The clearance rate is always the same as the urine flow.
F.
Rate of appearance of a substance in urine must equal:
its rate of removal from plasma
Rate of appearance in urine:
U(x) (conc of X in urine) X (V*) (urine flow rate)
Rate of removal from plasma:
P(x) (conc of X in plasma) X Clearance
Clearance =
(conc of X in urine / conc of X in plasma) X flow rate: part over whole times flow rate
Large clearance value indicates:
well removed from plasma
When does clearance = renal plasma flow?
when substance is completely cleared
Clearance for an substance that is not completely cleared is calculated using;
sum of filtration, reabsorption, and secretion
Substances hat are neither reabsorbed or secreted:
inulin and creatine
Estimate for GFR:
usually from plasma conc of creatinine, can also be done by dividing urine conc by blood conc and multiplying by the urine output in that 24 hour time frame
How is GFR controlled?
Starling Forces (hydrostatic vs. oncotic P’s)
Hydrostatic P:
force exerted by plasma fluid on cap walls
Oncotic P:
Osmotic pull exerted by plasma proteins
Afferent arteriole P vs. efferent:
17 mm Hg vs. 8 mm Hg
What does the ultrafiltration coefficient account for?
variations in permeability and s.a. of the cap
3 forces to bo considered in the the filtration capsule when calculating ultrafiltration pressure:
hydrostatic P’s of both GC and BS and ONLY oncotic P of GC (no protein in BS)
Precise equation for GFR:
K(f) X ultrafiltration P
ultrafiltration P:
P(GC) - P(BS) - pi (GC)
What changes the GFR bw the afferent and efferent arterioles?
difference in resistances
Cells of the DT and CD:
principal and intercalated cells
Portions of tubules in outer medulla:
Thick and DL, Thick AL, and CD
Portions of tubules in inner medulla:
ThinDL, ThinAL, and CD
Proteins forming tight junctions:
claudins
Are the N terminal and C terminal ends of the cloudiness facing the apical side?
N terminal
How many mOsmol per day must the kidney excrete?
600, regardless of water V excreted
Omolar clearance =
(Urine osmolarity / Plasma osmolarity) X Urine flow
Urine flow =
osmolar clearance + free water clearance
What info does the value of free water clearance provide?
ability of kidney to conc or dilute urine
Will C water be positive or negative if water is being generated in the tubule lumen?
positive
How do the kidneys create a positive free water in tubule lumen?
reabsorbing NaCl and urea in excess of water along nephron segments with low water permeability
How is water added to the the tubule fluid to create a positive free water in the tubule lumen?
Its not! NaCl and urea are taken out in a segment not permeable to water so it can’t follow
How does the kidney remove water from the tubule fluid to create a negative C water?
by allowing water to exit down its gradient into medullary interstitial fluid
Is more or less water being excreted if there is a neg C water?
less
How is the fluid in the loop of Henle diluted?
both the single effect and countercurrent multiplier
Effects of the the single effect and countercurrent multiplier:
dilute tubule fluid in loop of Henle and concentrate fluid in the medullary interstitium
in which segments of the tubule system is the concentration of the tubule fluid compared to that of the plasma remaining constant?
PT, early part of CD, and urine
in which segments of the tubule system is the concentraion of the tubule fluid compared to that of the plasma rising?
DL of loop of Henle, DT, and later part of CD
only segment of the tubule in which the concentraion of the tubule fluid compared to that of the plasma is decreasing:
Ascending limb of loop of Henle
ADH affects which part of the tubule system?
CD
How does ADH increase permeability of the CD?
inc # of AQP2 in pm
The macula dense of the ThickAL is adjacent to:
afferent and efferent arterioles entering G
1st half of PT paracellular pwy:
water, K, and Ca
1st half of PT transcellular pwy:
Lumen side: Na, Ca, glucose/P/ or AA and water in, H out plasma membrane: Na, Ca, (glucose/P/ or AA), HCO3-, water out and K, Na, H, and Ca in
Solutes reabsorbed via transcellular pwy in the 1st part of PT:
Na, P, glucose, AA
Via which route(s) does water follow along an osmotic gradient in the
both trans and para
What solutes are moved via solvent drag in the PT?
K and Ca via the para pwy
Major site of HCO3- reabsorption, HCO3- generation, and H+ secretion:
first half of PT
Movement of what solutes in the PT require energy?
Na, K, and H
2nd half of PT transcellular pwy:
Lumen: Na, Ca, Cl in, H and OA- (organic acid) out, plasma membrane: Na, K, Ca, and Cl out, K, H, Na, OA- in
2nd half of PT para pwy:
Cl, Na, K, Ca2+, H20
Site of transcellular organic acid secretion:
2nd half of PT
Site of Cl reabsorption:
2nd half of PT
T or F? Cl is reabsorbed in both 1st and 2nd half of PT.
F. 2nd half only and via both trans and para
Solutes that move across both para and trans pwys in the 2nd part of PT:
Na, Cl, K,
Solutes that move via the para pwy only in the 2nd part of PT:
Ca and water
Solutes that move via the trans pwy only in the 2nd part of PT:
H, OA-
What generates a transepi electrical gradient that promotes paracellular Na, K, and Ca reabsorption?
movement of unaccompanied Cl
T or F? Cl moves via the para pwy in the 2nd part of PT but water can not follow.
F. it does
How is Ca moved transcellularly?
bound to calbindin
What prevents in inc in intracellular Ca concentration when moving Ca through the cell?
it is bound to calbindin
In which portion of the cell does Ca/calbindin binding occur?
cytosol
How can Ca sequestered by proteins in plasma be released?
H+ in acidosis
is the thin DL permeable to water?
yes
Via what pwy does water leave the thin DL?
trans
Via which type of aquaporin does water flow out of the thin DL?
AQP1
t or F? The thin DL contributes tot he countercurrent multiplier mechanism.
T
AQP1 is found here and AQP2 is found here:
thin DL, CD
T or F? The Thin AL is permeable to salt.
T
T or F? The Thin AL is permeable to water.
F.
Why does the conc of the tubular fluid decrease as the fluid ascends in the ascending limb?
salt leaves via para pwy
Via what pwy does salt leave the ascending limb?
para
T or F? The Thin AL contributes to the countercurrent multiplier system.
T
What solutes are reabsorbed via the trans pwy in the Thick AL?
Na, K, and Cl
Is the Thick AL permeable to water?
no
T or F?The Thick AL contributes to both the single effect and the countercurrent mechanisms.
T
The single effect and the countercurrent mechanisms both contribute to:
urine concentration and transepi voltage that promotes reabsorption of Na, K and Ca via the para route
Solutes moved via trans pwy in the Thick AL:
Lumen: Na, K, Ca, and Cl in, K out, plasma membrane: Na, K, Ca, and Cl out, K, Na, and H in
Solutes moved via the para pwy in the Thick AL:
Na, K and Ca
The early DT is similar to the TAL except:
it is independent of K
Is the lumen side apical or basal?
apical
What provides the permeability to the apical side of the early DT?
Na/Cl contransporter (NCC)
What is the NCC?
Na/Cl co-transporter
What hormone increases the abundance of NCC?
aldosterone
What does increasing the abundance of NCC do?
inc salt reabsorption when BP is low
Solutes moved via the trans pwy in the early distal tubule:
Lumen side: Na and Cl in, plasma membrane: Na and Cl out, K in
What cells provide transcellular water permeability?
principal cells
Na permeability of the principal cells is provided by these channels:
ENac
T or F? ENac channel are found on both eh apical and basal side of the principal cells.
F. (check, only shown on apical side)
What provides an electrical driving force for transcellular K secretion ad Cl reabsorption in the principal cells?
na reabsorption
What channels provide an electrical gradient in principal cells by transporting K into the lumen?
ROMK
What channels provide an electrical gradient in principal cells by transporting Na into the cell from the lumen?
ENac
What solutes are transported via the paracellular pwy bw principal cells?
Cl-
What cells do all the fine tuning of urine/plasma content?
Principal
This is a major site of regulation in the tubule system?
Principal cells
Does aldosterone increase or decrease the activity of ENac when BP is low or K plasma conc is too high? ? what about ROMK? What about Na,K ATPase?
increase activity of all
Location of low pressure sensors:
wall of atria, R vent, and pulmonary vessels
T or F? An increase in dissension of the low-pressure sensors causes signals to be sent to the brainstem that stimulate sym n. activity.
F. dec in distension
Activation of low-pressure sensors leads to:
inc sym n. activity to inc Na reabsorption, stimulate renin/angiotensin/ aldosterone release to inc BP and Na reabsorption, stimulate ADH release to inc water reabsorption
These effects inc Na reabsorption:
sym n activity and renin/angiotensin/aldosterone release
T or F? ADH release leads to Na reabsorption.
F. water reabsorption
Location of high-pressure sensors:
walls of aortic arch, carotid sinus, and afferent arterioles
Activation of high-pressure sensors leads to:
reduce sym n. activity to increase Na excretion, inhibit ADH release to inc water excretion, heart cells release ANP and BNP
ANP and BNP are both:
natriuretic peptides
Effect of natriuretic peptides:
inc salt and water excretion
When is the RAAS activated?
dec Na/water reabsorption that lowers the ECF
From where is renin released?
granular cells, also produced and stored here
Where are the granule cells that store renin located?
afferent arteriole
What leads to the release of renin?
dec P in arteriole, low P in BV’s, dec Na delivery sensed by macula densa
What happens when the macula densa senses a reduction in Na delivery?
the macula densa stops sending inhibitory input to the renin producing cells
What intrinsic signaling capability does the macula dense have?
none
T or F? Renin is a protease.
T. helps generate Angiotensin II
Effects of Ang II:
sm contraction in BVs to inc BP during water/salt depletion, inc Na/H20 reabsorption by the PT, release of aldosterone
What hormone triggers the release of aldosterone?
Ang II
On what transporters does activated Ang II receps act?
Na/H exchangers, Na/K pump, and Na?HCO3- co-transporter
What type of hormone is aldosterone?
steroid hormone
Where is aldosterone both synthesized and secreted?
glomerulosa cells in cortex of adrenal gland
Triggers for aldosterone secretion:
inc levels of Ang II indicating dec Bp and Na delivery to macula densa, inc innervation of the adrenal cortex by symp nn. triggered by low P sensors in circulation
On which portions of the tubules does aldosterone exert its effects?
DT ad CD
Where does Ang II exert its effects?
PT and vasculature
2 types of intercalated cells:
alpha and beta
alpha intercalated cells:
secrete acid, maximize H+ secretion in acidosis
B-intercalated cells:
secrete base, secrete HCO3- in alkalosis
Which cells are active during acidosis?
alpha intercalated cells
What cells are active during alkalosis?
beta-intercalated
Difference bw alpha and beta intercalated cells in terms of location of channels:
alpha: Cl/HCO3- exchanger on plasma membrane and pumps H and Cl out into lumen, beta: Cl/HCO3- exchanger on lumen side and pumps H and Cl out into blood
On which side of the beta intercalated cell is the Cl/HCO3- exchanger?
luminal side
Changes in HCO3- concentration can lead to both:
metabolic acidosis and alkalosis
changes in dissolved CO2 concentrations can lead to both:
respiratory acidosis and alkalosis
When the efferent arteriole is constricted does P(GC) increase or P(GS)?
P(GC)
Ultrafiltration calculation:
Hydro P of G - Hydro P of Bowman’s Space - oncotic P of G
Who does aldosterone increase the Na permeability of the DT?
inc # of Na/Cl co-transporters in the plasma membrane
A dec in plasma Co2 conc wo a change in plasma HCO3- conc is:
resp alkalosis
This leads to dec in renal Na reabsorption:
ANP release
Why is it called a multiplier system/
Bc the effects of the gradient are multiplied by the countercurrent system.
In which limbs does water leave the tubule passively?
the descending limb and the CD
The characteristic yellow color of urine is attributed to:
urobilin
The kidneys are located:
behind the peritoneal membrane
Blood flow through the kidney includes a feature seen in only a few organs. What is it?
portal system
Glucose and amino acids are reabsorbed by:
sodium coupled symporter
Primary mode of transport of glucose across kidney epi:
symport with a cation
Primary mode of transport of urea across kidney epi:
passive reabsorption/diffusion
Primary mode of transport of small plasma proteins across kidney epi
transcytosis
These lie between and around the glomerular capillaries:
mesangial cells
The specialized cells found in the capsule epithelium are called __________. These cells have long cytoplasmic extensions called __________.
podocytes, foot processes
Damage to the renal medulla would interfere first with the functioning of the:
collecting ducts
If blood flow through the afferent arterioles increases:
stretch reflexes trigger vasoconstriction to reduce the flow
How and where is urea reabsorbed?
passively, proximal tubule
In the lumen of the proximal tubule, the Na+concentration __higher/less/same________ the Na+concentration inside the cells of the tubule epithelium.
is much higher than
One substance has no membrane transporters to move it but can diffuse freely through open leak channels if there is a concentration gradient. Initially, this substance’s concentrations in the filtrate and extracellular fluid are equal. Later, however, the active transport of Na+and other solutes creates a gradient by removing water from the lumen of the tubule where it is located. What substance is this?
urea
Which of the following “real” volumes plays the most important role in determining an optimum effective circulating volume?
plasma volume
Which of the following fluid compartments has the smallest volume?
plasma volume
What percentage of the body weight of a normal adult human is composed of water?
60%
Aldosterone stimulates sodium reabsorption
cortical collecting duct.
Tubulo-glomerular feedback is an important mechanism that
balances tubular filtration with reabsorption
The primary route for ion loss from the body is the __________ system
urinary
Cell volume (and therefore cell function) in most cells is dependent upon careful regulation of:
osmolarity of extracellular fluid
The two organ systems that work together to regulate mostaspects of the body’s water balance are:
urinary and cardiovascular
Where is most body water located?
inside cells
Kidneys regulate:
water loss, not water gain
When a body is dehydrated, water in the urinary bladder:
can be returned to the circulation directly.(?)
The hormone that regulates water excretion by the kidneys
ncreases water permeability throughout the kidney tubules
The primary osmoreceptors are located in the:
hypothalamus
Osmoreceptors depolarize after they __________ in response to __________ plasma osmolarity.
shrink, increase
2 fxns of atrial natriuretic peptide:
increases the GFR and inhibit release of renin
Thirst is triggered:
when plasma osmolarity is elevated above normal
Angiotensin I is converted to angiotensin II by enzymes primarily located in the:
blood vessels
The primary role of the carbonic acid-bicarbonate buffer system is:
the prevention of pH changes caused by organic and fixed acids
As a result of respiratory alkalosis:
the body retains less carbon dioxide
A person who suffers from emphysema will exhibit signs of:
resp acidosis
When the pH of body fluids begins to fall, proteins will
bind a hydrogen at the amino group
When the pH of the extracellular fluid declines:
the pH of the urine decreases
Dehydration may cause some ions to become concentrated. If a person was suffering from severe hyperkalemia, you would expect
the skeletal muscles to be unresponsive and cardiac arrest could occur
The hydrostatic pressure in the glomerular capillary is 68 mmHg. The hydrostatic pressure in Bowman’s capsule is 24 mmHg. The oncotic (colloid) osmotic pressure in the glomerular capillary is 18 mmHg. The filtration coefficient is 0.5 ml/min/mmHg. The net filtration pressure is _____ mmHg.
26
Which of the following is/are directly involved in autoregulation of the GFR?
A myogenic mechanism in which the afferent arteriole automatically constricts when it is stretched AND a feedback mechanism in which vasoactive chemicals released from the juxtaglomerular apparatus bring about afferent arteriolar vasoconstriction
The osmolality of the tubular fluid exiting the earlydistal tubule is always:
hypo-osmotic to plasma
Which of the following substances has the highest renal clearance?
Para-amino hippurate (PAH)
