case 7

Question 1

reabsorption

Answer 1

depends on active transport. filtrate out of Bowman into proximal tubule has the same solute concentration as extracellular fluid.

Question 2

active transport

Answer 2

Na+ from tubule lumen to ECF creates trans epithelial concentration. lumen is more - than ECF.
anions follow Na+ out of lumen. move through passive transport.
removal of Na+ and anions increases solute concentration in ECF. so water leaves tubule by osmosis

Question 3

loss of volume in lumen

Answer 3

increases concentration K+, Ca2+ and urea. when luminal concentration is higher than ECF solutes diffuse out of lumen, if the epithelium is permeable.

Question 4

reabsorption transport mechanisms

Answer 4

epithelial transport

paracellular transport

Question 5

epithelial transport

Answer 5

substances cross apical + basolateral membranes of tubule to reach interstitial fluid. electrochemical gradients determine transport mechanism.
solutes moving down gradient use open leak channels/ facilitated diffusion carriers.
molecules that need to be pushed are moved by primary/indirect active transport

Question 6

paracellular pathway

Answer 6

substances pass through cell-cell junction between two cells.
which route depens ond permeability of junctions and electrochemical gradient.
sodium: directly/indirectly involved in active/passive transport

Question 7

active reabsorption Na+

Answer 7

primary force for reabsorption. filtrate entering proximal tubule similar to plasma. higher Na+ than in cells.
Na+ can enter tubule cells passively.
apical movement of Na+ uses variety of symport and antiport proteins or open leak channels.
proximal tubule: Na+ - H+ exchanger (NHE) and epithelial Na+ channel play major role.
in tubule cell: Na is actively transported out of basolateral membrane in exchange for K+ by Na+-K+ ATPase.
basolateral K+ channel prevents K+ accumultaing. lets it move back into ECF.
apical membrane contains Na+-glucose cotransporter brins glucose into cytoplasm against concentration gradient.
basolateral: Na+ is pumped out by Na+-K+-ATPase and glucose diffuses out with facilitated diffusiont

Question 8

urea reabsorption

Answer 8

diffusion. initially concentration filtrate and ECF equal, active transport of Na+ + other solutes creates concentration gradient:
- when Na+ + others are reabsorbed, the transfer of osmotically active particles makes ECF more concentrated than filtrate remaining in lumen. water goes out lumen into ECF. up to this point no urea has moved. when water is reabsorbed concentration of urea increases and will move into ECF.

Question 9

RAAS

Answer 9

renin-angiotensin aldosterone system

key is juxtaglomerular cells. release renin.

Question 10

triggers juxtaglomerular cells

Answer 10

• low blood pressure sensed by granular cells
• JG cells triggered by sympathetic nerve cells during stress, triggers B1 adrenergic receptors
• macula densa cells. ability to sense sodium.

Question 11

RAAS liver

Answer 11

angiotensinogen
moves around nonactive. when it meets renin and activates angiotensinogen 1. moves through blood vessels. ACE turns 1 into 2

Question 12

angiotensinogen 2 places:

Answer 12

• smooth muscle in blood vessels, causing constriction
• kidneys hold more water, increased blood volume + stroke volume
• couple glands, pituitary gland. secreates ADH, also increases resistance of blood vessels.
• adrenal gland is triggered to produce aldosterone. promotes Na+ and water reabsorption in distal convoluted tubule.

Question 13

dehydration

Answer 13

leads to high blood concentration + low blood pH.
leads to increased respiration rate, high viscosity, increases resistance and mean arterial pressure.
triggers homeostasis.

Question 14

dehydration compensatory mechanisms

Answer 14

• conserving fluid to prevent loss
• triggering cardiovascular reflexes to increase blood pressure
• stimulating thirst.

Question 15

baroreceptors

Answer 15

sympathetic output

• heart rate goes up
• forces ventricular contraction increases under sympathetic stimulation. increased force of contraction combines with increased heart rate to increase cardiac output
• sympathetic activates vasomotor center, causing constriction
• vasoconstriction afferent arterioles in kidneys decreases GFR
• sympathetic at granular cells of kidneys increase renin.

Question 16

descreased periipheral blood pressure

Answer 16

directly decreases GFR, lower GFR conserves ECF volume

Question 17

paracrine feedback

Answer 17

causes granular cells to release renin. lower GFR decreases fluid flow

Question 18

granular cells respond to decreased blood pressure

Answer 18

by releasing renin. ensures increases production of angiotensinogen 2

Question 19

decreased blood pressure, blood volume, increased osmolarity and increased ANG 2

Answer 19

stimultae vasopressin and thirst centers of hypothalamus

Question 20

cardiovascular responses

Answer 20

combine increased cardiac output, peripheral resistance to raise blood pressure. does not mean pressure returns to normal.

Question 21

angiotensin 2

Answer 21

stimulation of thirst, vasopressin release, direct vasoconstriction and reinforcement of cardiovascular control center output. reaches adrenal cortex and attempt to stimulate aldosterone release.

Question 22

vasopressin

Answer 22

increases water permeability of collecting ducts, mmore water absorption. cant bring volume and osmolarity to normal

Question 23

intake of water

Answer 23

only mechanism for replacing lost fluid volume and restoring ECF.

Question 24

net result of all 4 mechanisms

Answer 24

• restoration of volume by conservation and intake
• maintenance of blood pressure through increased blood volume, cardiac output and vasoconstriction
• restoration of normal osmolarity by decreased Na+ absorption and increased water absorption and intake

Question 25

orthostatic hypotension

Answer 25

reflex that causes very fast constricting of blood vessels in legs when standing up quickly, so enough blood can go to your brain.

Question 26

dehydration histamine

Answer 26

production increased. causes bronchoconstriction + increased mucus build up. respiratory rate needs to be increased in order to maintain O2.

Question 27

osmolality

Answer 27

number of osmoles of solute in kg of solvent

Question 28

osmolarity

Answer 28

number of osmoles of solute in L of solution

Question 29

two types of countercurrent mechanisms determine urine concentration + volume

Answer 29

• multiplier: interaction between flow of filtrate through acending/descending limbs of nephron of juxtamedullary nephrons
• exchanger: flow of blood through ascending/descending portions of vasa recta

Question 30

medullary osmotic gradien

Answer 30

countercurrent and maintain an osmotic gradient

from cortex through depths of medulla

Question 31

countercurrent multipliers

Answer 31

nephron loops of juxtamedullary nephrons.
loop concentrates filtrate and dilutes it.
the more NaCl ascending limb extrudes more water diffuses out of descending.slatier filtrate becomes.

Question 32

countercurrent exchangers

Answer 32

vasa recta. entire length is permeable to water + solutes. blood withing vasa recta + surrounding interstitial fluid, blood in vasa recta remains isosmotic.
vasa recta do not undo osmotic gradient.
- prevent rapid removal of salt
- removing water

Question 33

formation of dilute concentrated urine

Answer 33

with medullary osmotic gradient concentration of urine not higher than 300 mOsm. not able to conserve water when dehydrated. ADH is released when dehydrated

Question 34

urea recycling

Answer 34

• enters filtrate via facilitated diffusion in ascending thin of nephron.
• filtrate moves up, collecting ducts reaborbs water –> urea left behind.
• when filtrate reaches collecting duct in medullary region, urea moves by facilitated diffusion out of tubule into interstitial fluid of medulla. forms pool of urea –> recycles back into ascending limb.

Question 35

ADH and urea

Answer 35

enhances urea transport of out duct. it increases urea recycling + strengthens medullary osmotic gradient, increasing concentration of urine.

Question 36

alcohol

Answer 36

is diuretic. encourages diuresis –> inhibits ADH

Question 37

renal clearance formula

Answer 37

C= (U x V)/ P
C= clearance
U= concentration substance in urine
V= urine formation flow rate
P= concentration substance plasma

Question 38

renal clearance description

Answer 38

describes volume of plasma completely cleared of a substance by kidney per unit time.
high: substance may be cleared almost completely.