Lecture 14

Question 1

Blood is filtered at the __________ and it produces a cell- and protein-free filtrate (glomerular filtration)

Answer 1

glomerulus

Question 2

• _____________: process of selectively moving substances from the blood into the filtrate
• _____________: process of selectively moving substances from the filtrate back into the blood

Answer 2

• tubular secretion
• tubular reabsorption

Question 3

the ______ is the most metabolically active part of the nephron, reabsorbs most of what was filtered….
- 100% _________
- 65% __________

Answer 3

proximal convoluted tubule (PCT)
- glucose; amino acids
- water; Na

Question 4

Tubular Secretion
- the transfer of materials from the ___________ capillaries (blood) to the renal tubule _______ (tubular fluid)
- opposite process of reabsorption

Answer 4

• peritubular; lumen

Question 5

Tubular Secretion is important for urine formation because….
- it helps gets rid of molecules NOT filtered at the _________ due to _____ size
- it is a major mechanism for elimination of most administered ________ and their _________
- it helps maintain the ______, _____-______, and other bodily fluid balances (secretion of K+, H+, NH4+, creatinine, urea)

Answer 5

• glomerulus; large
• drugs; metabolites
• ionic; acid-base

Question 6

2 routes that substances can follow to cross tubule cells and get reabsorbed into blood…
1. ______________: BETWEEN the cells
2. ______________: THROUGH the cells

Answer 6

1. Paracellular route
2. Transcellular route

Question 7

Structures that substances inside the renal tubular lumen must pass to be reabsorbed into the blood
- _____________ of tubular epithelial cells
- __________
- _____________ of tubular epithelial cells
- _______________
- ________________ of capillary

Answer 7

• apical membrane of tubular epithelial cells
• cytosol
• basolateral membrane of tubular epithelial cells
• interstitial fluid
• endothelial cells of capillary

Question 8

_____________: the maximum rate of reabsorption
- there are a _________ number of transport proteins–> limits the amount of solutes the renal tubule can ________
- Tm is reached when the transporters are _________
- each solute has its _____ ______

Answer 8

Transport maximum (Tm)
- LIMITED; reabsorb
- saturated
- own Tm

Question 9

Factors that limits the amount of solute the renal tubule can reabsorb and therefore the Tm
- the ________ of transport proteins available for that solute
- transport ___________ which occurs when all protein transporters are being used for the transport of that molecule

Answer 9

• number
• saturation

Question 10

________: the main function is to _______ all these things (such as glucose, amino acids, electrolytes) that your body did NOT intend to get rid of in the first place

Answer 10

PCT (proximal convoluted tubule); RECLAIM

Question 11

In the PCT…
- _________: generates a strong concentration gradient for sodium reabsorption; located on ______________

Answer 11

• Na+/K+ pump= Renal Na-K-ATPase; basolateral membraneD

Question 12

Direction of movement in Sodium-Potassium Pump
- it moves Na+ and K+ against large concentration gradients
- it moves ____ ions into the tubule cell where ____ levels are high
- it pumps _____ ions out of the cells and into ________ fluid

Answer 12

• potassium; K+
• sodium; interstitial

Question 13

How are organic solutes such as glucose and amino acids, as well as phosphates reabsorbed at the PCT
- via ____________ which transport _____ from the filtrate with another ______ (glucose, AAs)
- once solutes are inside the tubular epithelial cells… they cross the _________ membrane via _____ _________ _______

Answer 13

• solute-specific transporter; Na+; solute
• basolateral; specific membrane transporters

Question 14

3 ways Na+ is reabsorbed at the PCT
1. ___________ transport through the luminal (_____) membrane via a variety of __________ (transport Na+ with other ______, such as ______)
2. ____________ transport by _______ ____________ (=exchangers) which links secretion of ________ with reabsorption of ________
3. ____________ route across tubular epithelial cell _____ ________ (together with ______ ions) in _______ PCT

Answer 14

1. Transcellular; apical; symporters; solutes; glucose
2. Transcellular; Na-H antiporters; hydrogen; sodium
3. Paracellular; tight junctions; chloride; late

Question 15

The concentration gradient to move Na+ from tubular lumen to the cell is generated by…. _____________
- which continuously pumps Na+ _________ the cell; ________ Na+ inside the cell

Answer 15

Na-K ATPase
- outside; decreasing

Question 16

• Where is the Na+/H+ antiporter (Na+/H+ exchanger) located? _______________
• What is the direction of ion movement in the Na+/H+ antiporter? _______________
• Which hormone up regulates its expression and/or activity? ________________

Answer 16

• apical membrane of epithelial cells at the PCT
• H+ OUT; Na+ IN (contributes to Na+ reabsorption and body acid-base balance)
• Angiotensin II

Question 17

The reabsorption of salt and organic solutes creates a gradient favoring the passive movement of water by _________
- this is called “___________________________” because water is “obliged” to ________ solute movement

Answer 17

osmosis
- obligatory water reabsorption; FOLLOW

Question 18

• SGLT= ______________
• they are found in the renal tubule segment: __________, _____% glucose reabsorbed here
• function: responsible for the tubular _______________ of filtered glucose from the kidneys into the ___________

Answer 18

• Sodium Glucose cotransporters
• PCT; 100%
• reabsorption; bloodstream

Question 19

The primary. function of the Loop of Henle is to generate an _______ ________ that enables the collecting duct to concentrate the urine and conserve water

Answer 19

osmotic gradient

Question 20

• Which segment of the Nephron loop is permeable to water? ___________
• Which segment of the Nephron loop is impermeable to water? ____________
• Which segment of the Nephron loop is permeable to solutes? ____________
• Which segment of the Nephron loop is impermeable to solutes? ____________

Answer 20

• descending limb
• ascending limb
• ascending limb
• descending limb

Question 21

In the ____________ limb the reabsorption of large amounts __________ in the absence of water results in significant dilution of the tubular fluid—> this is why this segment of the nephron loop is considered “the ______ ________” of the nephron

Answer 21

ascending; sodium; diluting segment

Question 22

Thick Ascending Loop of Henle
- ___________ __________ are located on the ____________ membrane of epithelial cells

Answer 22

• Na+/K+/2Cl- symporter; apical (or luminal)

Question 23

Direction of ion movement in the Na+/K+/2Cl- symporter:
- all 3 ions are transported in the ________ direction
- from the ______ to the ______ of the cell
- reabsorption of Na+ is powered by a __________ _______ __________: it generates low Na+ concentrations within the tubular epithelial cells

Answer 23

• SAME
• lumen; inside
• basolatereal Na/K ATPase

Question 24

In the thick ascending loop of henle,
- how many potassium and chloride ions are transported together with sodium ions through co-transport?
Cl= ________
K= _______
Na= ______

Answer 24

2 (-2 charge)
1 (+1 charge)
1 (+1 charge)

Question 25

"Distal Tubule" - it includes two nephron segments 1. 2.

Answer 25

1. distal convoluted tubule (DCT) 2. Connecting tubule (CNT)

Question 26

- NCC= __________ - Located in ___________, subsegments 1 (_______) and 2 (__________) on _________ membrane of tubule epithelial cells - Function: transport _____ and _____ from the lumen to the cell

Answer 26

- NaCl Cotransporter - Distal convoluted tubule (DCT); early DCT; late DCT; apical - Na+; Cl-

Question 27

Main functions of cortical collecting duct - ______ ______ the amount of _________ -________ cells play an important role in this process--> controlled by ___________ -reabsorb ______ and ____ -secrete ____ - _____ homeostasis--> important role for ____________ cells -reabsorb ____ - secrete ____

Answer 27

- fine tuning; electrolytes -principal; aldosterone -Na; H2O -K+ - pH; type A intercalated -K+ -H+

Question 28

Main functions of medullary collecting duct - contributes to _____________ _________ _____ (_____ reabsorption) - ______ decision point for ______ reabsorption (urine concentration) - permeability to H2O depends on _____

Answer 28

- hyperosmotic medullary ISF; urea - FINAL; water - ADH

Question 29

The late DCT and cortical CD are relatively impermeable to water and solutes unless influenced by _______________

Answer 29

hormones

Question 30

ENaCs= ___________ - located: __________ and ___________

Answer 30

Epithelial Sodium Channels - late distal convoluted tubule (DCT 2) and cortical collecting duct (CD)

Question 31

3 regions of the nephron that are collectively termed the "aldosterone-sensitive distal nephron" 1. 2. 3.

Answer 31

1. Late Distal Convoluted Tubule (DCT 2) 2. Connecting Tubule (CNT) 3. Cortical Collecting Duct (CCD)

Question 32

___________: hormone that controls water reabsorption, and therefore, urine concentration in the _____

Answer 32

ADH (Antidiuretic hormone, aka vasopressin); CD

Question 33

Two factors that allow the kidney to produce concentrated (hypertonic) urine 1. _______ acting on the ___ and ____ to increase water permeability: "_________ water reabsorption" 2. a ________ _______ ________ in the interstitial fluid of the _____ ________ that drives the reabsorption of water by osmosis

Answer 33

1. ADH; DCT; CD; "facultative" 2. medullary osmotic gradient; renal medulla

Question 34

To produce concentrated urine... you need to reabsorb _________ water

Answer 34

MORE (the urine will contain less amount of water so the solutes will be concentrated)

Question 35

_____ in the ______ you can find more concentrated interstitial fluid

Answer 35

DEEP; medulla

Question 36

Three mechanisms that help create or maintain the medullary osmotic gradient 1. a _______ ______ _______ in the nephron ______ of _________ nephrons 2. The ________ of _______: it passively diffuses into the interstitial fluid of the medulla from the ______ - this ______ will be taken back into the tubular fluid at the nephron _______ 3. A _________ ________ in the _____ ______

Answer 36

1. countercurrent multiplier system; loops; juxtamedullary 2. recycling; urea; CD - urea; loop 3. countercurrent exchanger; vasa recta

Question 37

Countercurrent Multiplier System - located: nephron _____ of __________ nephrons - called multiplier because it multiplies the _________ deep in the ______ - establishing an interstitial osmolality gradient from ______ mosmol/kg (in the ____ similar to plasma) to >_______ mosmol/kg (in the ________ at the tip of the renal papilla)

Answer 37

- loops; juxtamedullary - osmolarity; medulla - 300;cortex; 1200;medulla

Question 38

in the descending loop of henle, water is drawn from the tubular fluid through ___________, following an osmotic gradient created mainly by ________ ion

Answer 38

aquaporins; sodium (Na+)

Question 39

in which limb of the nephron loop is the tubular fluid more concentrated in solutes?

Answer 39

descending loop because water leaves and NaCl remains (filtrate becomes progressively more concentrated as it reaches bottom of the nephron loop)

Question 40

- The descending limb is __________ to solutes, including Na+ - The ascending limb we can find ________ transporters - this is why sodiums ion leave the ________ limb of the nephron and not before

Answer 40

- impermeable - Na+/K+/2Cl - ascending

Question 41

What is responsible for increasing the interstitial fluid's osmolarity of the medulla?

Answer 41

- pumping sodium outside the tubule

Question 42

Countercurrent multiplier vs. Countercurrent exchange - the countercurrent multiplier at the nephron loop is mainly responsible for creating the ______ ______ - the countercurrent exchanger does _____ create the _____ ________, but ________ it by (1) preventing ____ removal of salt from the medullary interstitial (2) removing reabsorbed ______

Answer 42

- medullary gradient - NOT; medullary gradient; preserves (1) rapid (2) water

Question 43

The countercurrent exchange - the water reabsorbed at the descending limb reenters the circulatory system through the ____ ______ - as the blood flow in these capillaries is _____, solutes that are reabsorbed into the bloodstream have _____ time to diffuse back into the interstitial fluid, maintaining the ______ concentration gradient in the _______

Answer 43

- vasa recta - SLOW; ample; solute; medulla

Question 44

______ passively diffuses into the interstitial fluid from the CD, contributes to the _________ _______ _______

Answer 44

urea; medullary osmotic gradient

Question 45

Obligatory water reabsorption - water is ______ by osmosis to follow ______ that have been reabsorbed - takes place in the ______ and ______ _________ - _______ control this with _________ - _____ % of water

Answer 45

- obliged; solutes - PCT; descending limb of nephron loop - CANNOT; hormones - 85%

Question 46

Facultative water reabsorption - regulated by ______; water is reabsorbed considering the plasma osmolarity (fluid balance of the individual) - takes place in the ___ ______ and _____ - ____% of water

Answer 46

- ADH - late DCT; CD - 15%