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Renal > Physiology > Flashcards

Physiology Flashcards

1
Q

osmolarity is… and how do you calculate it?

A

no of osmotically active particles in solution

no of particles x molar concentration

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2
Q

osmolarity of body is

A

300mmol/l

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3
Q

tonicity is…

A

effect solution has on cell- hypo (inc cell size), hyper (dec cell size), isotonic (normal)

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4
Q

what are the 2 components that make up total body water

A

ECF- interstitial fluid (80%), plasma, lymph

ICF

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5
Q

what are some tracers used to measure vol distribution and how to measure?

A

TBW- 3H2O, ECF- inulin, plasma- labelled albumin

unknown V= dose/ sample [ ]

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6
Q

T/F: ICF has more Na+

A

F: ECF- more Na+, Cl- and HCO3-. ICF- more K+

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7
Q

what is electrolyte balance important?

A
  1. total electrolyte [ ] can directly affect water balance
  2. [ ] of individual electrolytes can affect cell function

(e.g. small changes in K+ may result in cardiac arrest, small changes in Na+ may results in inc BP)

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8
Q

name some functions of the kidneys

A

water balance, salt balance, plasma vol & osmolarity maintenance, acid-base balance, metabolic waste excretion, renin & erythropoietin secretion, vitD to calcitriol conversion

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9
Q

name the functional unit of the kidney, what it does, and its blood supply

A

the nephron- filters, reabsorbs and secretes (from capillaries > tubules and vice versa).

BS: artery > afferent artery > glomerulus > efferent arteriole > peritubular capillaries > vein

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10
Q

T/F: not all of the nephron is found in the medulla

A

T: only loop of henle and collecting duct found in medulla

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11
Q

what is the difference between juxtamedullary and cortical nephrons

A

juxtamedullary has much longer loop of hele

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12
Q

what is the juxtamedullary apparatus

A

region where efferent and afferent arterioles bifurcate. contains the granular cells (secrete renin) and the macula densa which detects salt levels in tubule fluid- main regulators of downstream blood flow through capillaries

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13
Q

what are the methods of filtering blood

A

glomerular filtration (occurs in glomeruli in bowman’s capsule), tubular reabsorption and tubular secretion

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14
Q

know how to calculate rate of filtration and rate of excretion, as well as rate of reabsorption and rate of secretion.

what is an important golden rule when it comes to net reabsorption and net sceretion

A

if rate of filtration > rate of excretion= net reabsorption has taken place

if rate of excretion> rate of filtration= net secretion has occurred

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15
Q

how much plasma is filtered in glomerulus

A

20%

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16
Q

what are the 3 barriers proposed by glomerular membrane that block filtration

A

glomerular capillary endothelium, basement membrane, slit processes of podocytes

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17
Q

there are 4 forces that allow for net filtration pressure (driving force of plasma across glomerular membrane)- 2 oppose and 2 drive, these are?

A

favouring: glomerular capillary BP, bowman’s capsule oncotic pressure
oppsoing: bowman’s capsule hydrostatic pressure, capillary oncotic pressure

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18
Q

how to calculate net filtration pressure

A

net filtration= add up forces favouring filtration - forces opposing filtration

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19
Q

GFR is… and how to calculate

A

rate at which protein-free plasma is filtered from glomeruli into BC per unit time

GFR = Kf x net filtration pressure
normal GFR= 125ml/min

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20
Q

2 regulators of blood flow and GFR

A

extrinsic: sympathetic control via baroreceptor reflex- constriction of afferent arteriole

intrinsic:
- myogenic mechanism: if vascular SM is stretched it contracts thus constricting arteriole
- tubuloglomerular feedback system: ^ GFR= macula densa detects inc NaCl so releases vasoactive chemicals, SM contraction of afferent arteriole

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21
Q

what may have affects on GFR

A

anything affecting glomerular capillary BP, bowman’s capsule oncotinc pressure, bowman’s hydrostatic pressure, glomerular capillary oncotic pressure
e.g. diarrhoea inc oncotic pressure of glomerular capillary so dec GFR

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22
Q

what is key to markers

A

should be filtered but not secreted or reabsorbed

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23
Q

how to measure clearance of substance

A

clearance of X=( [X] in urine x Vurine ) / [X] plasma

ANS= ml/min

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24
Q

what are 2 main clearance markers (GFR markers)

A

inulin (exogenous so hard to administrate), creatinine (slightly secreted so close approx for GFR)

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25
Q

T/F: glucose is completely reabsorbed

A

T: clearance value of 0

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26
Q

urea filtration, secretion and reabsorption?

A

filtered, partly reabsorbed and not secreted. therefore clearance

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27
Q

what do we mean by secretion and reabsorption

A

secretion- from peritubular caplirries to renal tubule lumen

reabsorption- from renal tubule lumen to peritubular capillaries

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28
Q

what marker is used for renal plasma flow and its normal value

A

paro-amino hippuric acid (exogenous anion)

650ml/min

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29
Q

what is the equation for filtration fraction

A

FF= GFR/renal plasma flow (how much plasma entering glomeruli is being filtered- normal value 20%)

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30
Q

what does the glomerular filtrate not contain that the blood does

A

doesn’t have RBCs, large plasma proteins

31
Q

the first fluid to reach proximal tubule is…

A

iso-isosmotic

32
Q

2 pathways for Proximal tubule absorption

A

transcellular (through tubular lumen > epithelial cells)

paracellular (pass through tight/leaky junctions)

33
Q

what are 3 carrier-mediated membrane transports

A

1y active transport
2y active transport (ion coupled)
facilitated diffusion

34
Q

Na movement in PT?

A

Na moves via Na/K pump, Cl- follows transcellular as electrical gradient formed, and water follows down osmotic gradient

35
Q

what is a transport maximum

A

maximum rate at which a pericellular substance can be reabsorbed. once reached excretion of substance inc

36
Q

what is the main function of loop of henle

A

creates cortico-medullary concentration gradient allowing formation of hypertonic urine

37
Q

the descending limb is permeable to ___ but not to ___

A

H2O, not to NaCl

38
Q

the ascending limb is prone to ___ reabsorption but impermeable to ___

A

NaCl, H2O

39
Q

how does Na reabsorption occur in ascending loop

A

triple co-transoporter

40
Q

describe what happens in LH

A

fluid enters iso-isometricly into descending limb > H2O lost, no Na picked up > inc osmolarity (concentrated filtrate) > NaCl reabsorption in spending limb but no H2O lost so osmolarity dec again to 100mmol

41
Q

if tubular osmolarity dec, what happens to interstitial fluid osmolarity

A

inc

42
Q

what is the other substance that adds solute to IF

A

urea (2-solute hypothesis)

43
Q

why is it important for urine to be dilute when it enters the collecting duct

A

allows kidneys to produce urine of different volumes and [ ] according to how much ADH present in blood, creates hypertonic solution (less H2O- allows for more H2O to be reabsorbed into body)

44
Q

what is the counter current exchanger

A

vasa recta/ capillary blood equilibrates with IF. does this my inc osmolarity as dips into medulla (NaCl retention and H2O loss), and dec osmolarity as climbs back up into cortex (NaCl loss, H2O gain)

45
Q

what happens in collecting duct

A

progressively inc osmolarity as it descends through medulla

46
Q

what controls fluid and salt retention in distal tubule and collecting ducts

A

hormones- specifically ADH (water), aldosterone (Na), PTH (dec phosphate, inc Ca reabsorption)

47
Q

what happens in distal tubule

A

early segment: inc NaCl reabsorption via Na-K-2Cl transport

late segment: Ca2+ reabsorption, H+ secretion

48
Q

T/F: distal tubule has high permeability to H2O and urea

A

F: has low permeability to H2O and urea

49
Q

what happens in collecting ducts

A

low ion permeability, H2O and urea permeability influenced by ADH

50
Q

high ADH…

A

high ADH > high water permeability (inc reabsorption) > hypertonic urine (concentrated)

51
Q

what is a measure of concentrated urine in the collecting ducts

A

1400mosmol/L

52
Q

low ADH…

A

Low ADH > not permeable to H2O (less H2O reabsorption) > diluted urine (50mosmol/L)

53
Q

ADH Hormone

A

secreted by posterior pituitary

signal of dehydration is trigger to release (osmorecpetors in brain), stretch receptors in left atrium

binds to T2 receptors on basolateral membrane of cells in DT and CD > cascade initiated recruiting AQP2s to apical membrane

54
Q

aldosterone hormone

A

secreted by Cortex of adrenals

stimulus is inc K+ or dec Na+ or RAAS activation

effect is to inc Na+ reabsorption, inc K+ secretion

55
Q

when is RAAS activtaed

A

if there is a dec in NaCl, ECF vol or Arterial BP

56
Q

3 mechanisms by which 3 renin is stimulated

A
  1. reduced pressure in afferent arterioles
  2. macula densa detects less NaCl
  3. inc sympathetic activity as result of reduced BP (and granular cells directly innervated by sympathetic system)
57
Q

Aldosterone inc Na reabsorption by…

A

inc no of Na/K pumps on basolateral membrane, and inc Na co-transport at apical membrane

58
Q

3rd hormone involved in fluid and salt retention is…

A

atrial natriuretic peptide (ANP)- stimulated by stretch receptors in atrial muscles cell due to inc plasma vol. act to excrete Na+ and acts on CV to lower BP

59
Q

micturition physiology…

A
  1. micturition reflex: bladder can accommodate 250-300ml. once this is reached stretch receptors stimulated in detrusor muscle- simultaneous contraction of muscle and relaxation of sphincter= micturition
  2. voluntary control: can actively tighten external sphincter
60
Q

abnormal pH levels

A

<7.35-acidic

>7.45- alklaotic

61
Q

what must = what for a chemical reaction to take place

A

pK (dissociation constant)=pH

62
Q

how is H+ continually added to body

A
  1. carbonic acid formION
  2. inorganic acid produced during breakdown of nutrients
  3. organic acids resulting from metabolism
63
Q

what is a buffer system

A

made up of 1 substance that adds H+ and one that removes H+

64
Q

how do you rearrange pk=pH to solve for pH

A

pH= pK + log [A-]/ [HA]

65
Q

carbonic acid is a…

A

buffer

66
Q

kidneys control bicarbonate, they do this by…

A

variable reabsorption of HCO3-
kidneys add new HCO3-

both dependent on H+ secretion into tubule

67
Q

how is HCO3- reabsorbed

A

cannot pass into cell so must bind to H+ > H2CO3 > dissociates to CO2 + H2O > crosses membrane via carbonic anhydrase > HCO3- reformed intracellular > leaves at BL membrane via Na co-transpoter

68
Q

in what 2 forms is HCO3- replenished

A

titratable acid- H2PO4- and ammonium- NH4+

69
Q

what 3 things must occur for a person to have norma acid-base balance

A
  1. plasma pH close to 7.4
  2. HCO3- close to 25mmol/l
  3. arterial pCO2 close to 40mmHg
70
Q

compensation is…

A

restoring pH to 7.4 asap, correction is restoration of HCO3- and pCO2

71
Q

respiratory acidosis…

A 
retention of CO2
emphysema, restricted lungs
^H+, pH <7.35, pCO2 >45
compensation: renal- H+ secretion, HCO3- reabsorbed and inc production 
correction: resp rate back to normal (
72
Q

respiratory alkalosis

A 
loss of CO2
hyperventilation, altitude hypoxia 
dec H+, pH >7.45, pCO2 <35
compensation: renal- dec H+ secretion, HCO3- excreted and not produced 
correction: normal ventilation
73
Q

metabolic acidosis

A

excess H+ for reasons other than pCO2, most common
acid ingestion, DKA, excessive base (HCO3-) loss
pH: <7.35, HCO3- low
compensation: resp- inc resp- inc CO2 blown off
correction: kidneys- H+ secretion, HCO3- reabsorption and production

74
Q

metabolic alkalosis

A

loss of H+
HCl loss, alkali ingestion
pH >7.45, HCO3- inc
compensation: dec vent (inc PCO2 retention in lungs)
correction: renal- inc HCO3- excretion ( a lot so overflows into excretion), no new HCO3- production

Renal (16 decks)

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