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Human Body_TP > Renal System Physiology > Flashcards

Renal System Physiology Flashcards

1
Q

what determines the amount of water in each body compartment?

A

amount of solute in each compartment and the permeability of water

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2
Q

2 types of pressure

A

-osmotic and hydrostatic
-often oppose each other

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3
Q

osmotic pressure

A

-semipermeable membranes permeable to water but not solutes
-in compartment A you have a lot of solute —> water moves from one compartment to another to normalize solute concentrations
-change in volume of both compartments for solute concentration to normalize

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4
Q

hydrostatic pressure

A

-force pressure to force water through semipermeable membrane
Ex. blood pressure
-create osmotic pressure since the concentration of solutes in compartments is different

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5
Q

if osmotic pressure is driven by the number of solute particles in each body compartment, what determines the total amount of salt in the intracellular compartment?

A

-osmotic is driven by the number of solute particles that are determined by the active transport processes in the intracellular compartments
-inside the cells you have different concentrations of sodium and potassium than you do outside

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6
Q

what determines the total amount of salts in the extracellular compartment?

A

determine ionic content by balancing outflow and intake —> what you take in = what you put out

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7
Q

functions of the kidney

A

-regulation of volume and composition of body fluids
-primary regulator of BP —> handles NaCl and water (proven by every single monogenic or single mutation for high/low BP is expressed in the collecting duct of the distal kidney)
-maintains homeostasis for K, NaCl, phosphate, Cl, acid-base balance
-produces hormones like renin, angiotensin II, erthropoetin, active form of vitamin D
-synthesizes important compounds like ammonium and bicarbonate
-secretes toxins
-overall regulates homeostasis

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8
Q

homeostasis

A

preservation of constant internal environment

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9
Q

steady state

A

parameters aren’t changing

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10
Q

set point

A

optimum conditions that allow organism to perform normal bodily functions

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11
Q

sensors, mediators, effectors

A

-correct and help body to homeostatic value
-a lot in the kidney and extra-renal to talk to kidney

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12
Q

what are the two types of sensors related to the kidney?

A

extra-renal and renal

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13
Q

sensors

A

pressure receptors send info to the kidneys and kidneys themselves have different pressure and mechano receptors plus feedback loops
Ex. phenotype of patient with renal failure —> everything goes wrong in functions like regulating NaCl, water, K, acids and bases balance

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14
Q

structure of the kidney

A

-cortex- outer part
-medulla- inner part
-nephron- functional unit of the kidney with ~1.3 million of them

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15
Q

nephron

A

-begins @ the glomerulus, bundle of capillaries that takes blood and filters it to the filtrate that will eventually become urine
-filtrate flows down the proximal tubule

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16
Q

how much do the kidneys filter per day?

A

180 liters but majority of it is reabsorbed

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17
Q

what is the equation for the excretion of a substance?

A

excretion of substance = filtration - reabsorption + secretion

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18
Q

what is the job of the glomerulus?

A

form primary urine

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19
Q

proximal tubule

A

fluid first encounters the proximal tubule, which reabsorbs 67% of the total filtrate

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20
Q

loop of henle

A

reabsorbs 25% of the filtrate

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21
Q

distal tubules

A

reabsorbs like 5% of the filtrate

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22
Q

collecting duct

A

reabsorbs 5% of the filtrate

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23
Q

filtration-reabsorption diagram

A

filter the whole ECF 12-13x a day and the amount secreted is minuscule —> reabsorbing like 99%

24
Q

hydrostatic pressure + osmotic pressure in filtration

A

-apply hydrostatic pressure, shove water through, and create opposing osmotic pressure that will want to move water back
-balance will determine how much filtration occurs

25
Q

filtration: organization of renal vasculature

A

-in glomerulus, the hydrostatic pressures are high on both sides with some going down efferent arteriole
-in a healthy person, protein should not get through the capillaries —> oncotic pressure is higher at the end of the capillaries and you have opposing oncotic pressure to oppose filtration
-based on oncotic pressure differences, you would expect water to move from the space outside the glomerular capillaries back in but based on hydrostatic pressures you would expect the water to move from glomerular capillaries down to proximal tubules
-balance of these pressures will determine how much filtration occurs
-only place in the body where arteriole and capillary bed instead of vein you have another arteriole and capillary bed —> keeps the hydrostatic pressure high on both sides
-capillaries that come later, the hydrostatic pressure drops quickly since there is a vein on the other side

26
Q

glomerular filtration rate (GFR)

A

GFR = Kf*[(Pgc-Pbs)-(pigc-pibs)] where Kf is the ultrafiltration coefficient

27
Q

peritubular capillaries and glomerular capillaries

A

-peritubular capillaries they profuse the kidney
-glomerular capillaries with arterioles on both sides —> hydrostatic pressure remains high and drives filtration despite oncotic pressure rising
-in peritubular capillaries, the hydrostatic pressure is low since they are between an arteriole and renal vein —> allows for passive reabsorption

28
Q

filtration barrier

A

-number of different obstacles substances have to get through to pass from capillary lumen to bowman space
-Na and water can go freely
-larger molecules get stuck in the capillary lumen
Ex. collander with spaghetti stuck and water gets through

29
Q

characteristics of the ultrafiltrate

A
  1. size- size is an issue if the molecules are too big to pass through
  2. charge- capillary is filled with proteins that have a lot of negative charges that repel proteins
  3. shape- you could have certain proteins that are rod-shaped and able to pass through the small holes
30
Q

crossing the filtration barrier: size matters!

A

concentration ratio of filtrate:blood of 1.0 means freely filtered but to molecules that are larger they get excluded from urine

31
Q

how to know if there is a glomerular problem?

A

a lot of protein in the urine —> means the barrier is broken or defective

32
Q

clearance

A

amount of plasma that must be cleared of a substance to account for the appearance of that substance in final urine

33
Q

estimating the GFR

A

-GFR is assessed by measuring the clearance of a substance that is freely filtered by the glomerulus but is neither reabsorbed or secreted in nephrons
-urinary excretion rate = filtration rate - reabsorption rate + secretion rate
-amount excreted in the final urine = amount filtered at the glomerulus

34
Q

inulin

A

-substance that is freely filtered by the kidney but not reabsorbed, secreted or metabolized
-exogenous substance that is given to patients —> see how it is cleared to see if the filter is working

35
Q

creatinine

A

in clinic, they use creatinine to estimate renal function and secreted by the proximal tubule —> amount can sometimes change in disease and mask changes in glomerular filtration rate

36
Q

proximal tubule reabsorption

A

glucose, amino acids, and proteins (those with small molecular weights can get to the filtrate) —> reabsorbed rigorously right away in proximal tubule (body spent ATP to make these and don’t want to lose them)
-should not be in the final urine

37
Q

uncontrolled diabetes

A

glucose in the final urine —> transport maximum in the proximal tubule so anything above it then it can’t get sucked back up, it will reabsorb as much as it can but excess gets to the urine

38
Q

urea

A

-urea is reabsorbed —> secreted —> reabsorbed again, movement of urea is important for how the kidneys concentrate urine
-moves in a cycle in the nephron

39
Q

Na and water

A

-in the beginning, Na and water are on top of each other then separate after the loop of Henle (isoosmotic reabsorption)
-later part of the nephron you separate handling the Na and water —> early on reabsorbed together then for the fine tune control of kidney separate handling
-for Na, 67% reabsorbed by the proximal tubule and 25% by loop of Henle last part then last bits reabsorbed by distal part of nephron —> 67% and 25% don’t change no matter what but the smaller segments are constantly changing and refining how much Na gets reabsorbed

40
Q

what regulates Na handling?

A

doing fine tuning in response to hormones that are coming from other parts of the body like ANP, aldosterone, renin, and angiotensin

41
Q

water

A

-reabsorbed isoosmotically with Na then separated —> how much water you reabsorb depends on how much you drink
-change in osmolarity in tubular fluid over plasma —> doesn’t change in proximal tubule, urine is initially concentrated in the loop of Henle so two different lines show different hydration statuses
-high/low water intake —> you can excrete urine with drastically different osmolarity

42
Q

potassium

A

-reabsorbed in the proxmal tubule then fine tuning happens in the distal part of the nephron
-guarded carefully so the kidney has the ability to reabsorb K or secrete a lot of it to get rid of it
-in low dietary intake and normal to high dietary intake —> reabsorption by the proximal tubules is the same @ 80% but in the distal part you can continue to reabsorb in the low dietary intake or secrete massive amounts of K
-urine secretes whatever value of K it needs to do to keep values of K in the blood

43
Q

what does a non-polar cell do?

A

moves ions in and out of the cell

44
Q

what do epithelial cells do?

A

-transport salt and water either into or out of a compartment
-regulate intercellular concentrations of solute and move solutes from the basolateral side across to the apical side without messing up your internal intercellular salt concentrations
-handle by structural polarity (localize proteins differently to transport in tandem) with apical and basolateral side —> recognize protein as apical or basolateral, traffice properly, and keep where you put it

45
Q

what determines the functional properties of epithelial cells?

A

distributions of ion transport proteins

46
Q

absorptive epithelium

A

-occurs in the thick ascending limb
-put the Na-K-ATPase on the basolateral side
-reabsorb- you put the contransporter of NaK2Cl on apical side to move fluids in and you need recycling K channel on apical side since the K is limiting
-Cl exits on basolateral side with Na

47
Q

secretory epithelium

A

-occurs in lung epithelium
-take the same transporters and orient them differently for a different outcome with the Cl channel on the apical side, cotransporter on basolateral side along with the recycling K channel —> allows for net secretion instead of net absorption

48
Q

epithelial cell surface specializations facilitate transport

A

microvilli brush border in proximal tubule —> helps increase surface area for linear distance to pack in transporters plus invaginations to basolateral side to pack in the Na,K-ATPase to drive transport

49
Q

absorption of NaCl

A

-in distal nephron, reabsorb Na and secrete K —> Na,K-ATPase on basolateral side and channel for Na on apical side and channel for K on apical side
-in thick ascending limb, Na-K-2Cl cotransporter on apical side to drive reabsorption of Na and Cl
-K is recycled through K recycling channel

50
Q

how is water transported?

A

-passive and follows Na
-isosmotic reabsorption- when Na moves, water follows so the volume of compartments changes but the concentrations do not
-in the proximal tubule, Na and water are reabsorbed together

51
Q

Gatorade

A

-UF football coach asked robert cade to observe the football players and he found that they were losing 18 lbs/day, which was mainly water loss
-not enough to just give water —> replace water isosmotically with water that was isosmotic to plasma with Na, K, and Cl at the same concentration as plasma, which would be easier for the body to digest

52
Q

hyperosmotic absorption

A

later in the tubule, we can separate Na and water by reabsorbing salt and make the membrane impermeable then remove salt and water can’t follow

53
Q

what does the kidney use to reabsorb a lot of the things it needs to?

A

-big concentration gradient —> needs a secondary active transport
-uses Na-glucose cotransporter- uses concentration gradient of Na to co-reabsorb glucose and reabsorb amino acids
-by using Na,K-ATPase to set up concentration, but good Na pump allows you to use secondary active transport to take advantage of Na reabsorption to drive glucose reabsorption and reabsorption of phosphate
-anti-porters like Na-H exchanger where reabsorption of Na can be coupled through secondary active transport to secretion of H ions

54
Q

proximal tubule

A

-S1 segment- most transportative with more mitochondria, brush border
-S2- smaller brush border and a little less mitochondria
-S3- high affinity for last molecule of glucose
-most reabsorption happens before the 50% mark in length of the nephron
-secretes compounds the body wants to get rid of

55
Q

penicillin + probenecid

A

-during WW2, penicillin was found and saved lives but not much of it was left in the body —> got secreted quickly out of the proximal tubule then probenecid is secreted by the same transporter as penicillin
-co-administered the probenecid with the penicillin and found it competitively inhibits the transporter and allows the penicillin to stay in the body longer

56
Q

loop of henle (middle portion of nephron)

A

-differential absorption of water with NaCl, which concentrates urine
-on the way down, water is going out to the medulla
-on the way up, no longer water permeable

57
Q

final portion of the nephron

A

-absorb NaCl and secrete or absorb K
-water can be absorbed or not depending on the presence of ADH —> ADH determines the water channels in the membrane
-water permeability in the first segments is very high then less in the middle and at the end it depends on the presence of ADH that determines dilution or concentrated urine
-ADH regulates thirst drive and water permeability

Human Body_TP (25 decks)

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