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BS1016 Physiology > Renal system > Flashcards

Renal system Flashcards

1
Q

what are the conditions in the internal environment controlled by the kidneys

A

concentration of waste products

concentration of ions

pH

volume and pressure

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2
Q

what are the functions of the renal system

A

regulates water homeostasis

regulates ECF volume

regulates concentration of most ECF ions

excretes waste products

regulates pH by adjusting urinary acid excretion

produces and activates hormones

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3
Q

how does the kidney react to hypoxia conditions

A

as blood carries RBC to kidneys, low O2 levels detected by Hif-alpha subunit > combines with Tif-beta to form hypoxia response element > produce erythropoietin > stimulate RBC production in bone marrow > increase O2 carrying capacity

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4
Q

structure of aquaporin 1

A

6 transmembrane domains

exists as tetramer with each subunit having its own water pore

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5
Q

what are the defence mechanisms against changes in ECF [H+]

A

buffer system: reversible reaction between HCO3- and H+

respiratory control: controlling concentration of CO2 in the blood > in turn control [H+]

renal control: regulate pH by excreting excess H+ and reabsorbing bicarbonate ions

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6
Q

how to find plasma clearance rate of a substance

A

(urine conc of a substance x urine flow rate) / plasma conc of a substance

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7
Q

commonly used substances for plasma clearance test

A

inulin, creatine, para-aminohippuric acid

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8
Q

causes of kidney failure

A

high blood pressure and diabetes

infection, toxic substances, autoimmune response

urinary tract obstruction

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9
Q

types of kidney failure

A

acute: rapid loss of renal function, condition may be reversible

chronic: progression in disease of kidneys; gradual loss in renal function; condition is not reversible

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10
Q

major consequences of renal failure

A

uremia: accumulation of waste products

salt and water retention

metabolic acidosis

anemia

endocrine disorder

disorder of mineral metabolism

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11
Q

difference between cortical and juxtamedullary nephrons

A

glomeruli of cortical lie in outer layer of cortex, while that of juxtamedullary lie on inner layer

loop of henle of cortical dip slightly into medulla while that of juxtamedullary plunges entirely through medulla

peritubular capillaries of juxtamedullary forms vasa recta, but not for cortical

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12
Q

what are the 3 basic renal processes

A

glomerular filtration > tubular reabsorption > tubular secretion

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13
Q

what is the pathway of substances to be filtered

A

pores between and fenestrations within endolethial cells of glomerular capillary > acellular basement membrane > filtration slits between the foot processes of podocytes in inner layer of Bowman’s capsule

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14
Q

what are the forces involved in glomerular filtration

A

glomerular capillary blood pressure (55): pressure exerted by blood within glomerular capillaries

plasma-colloid osmotic pressure (30): since plasma proteins cannot be filtered > conc of H2O in bowman’s capsule greater than glomerular capillaries > osmosis down concentration gradient > opposes filtration

bowman’s capsule hydrostatic pressure (15): pressure exerted by fluid in bowman’s capsule against glomerular capillaries

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15
Q

what are the mechanisms regulating GFR

A

auto regulation: prevent spontaneous changes in GFR

extrinsic sympathetic control: aimed at long term regulation of arterial blood pressure

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16
Q

mechanisms responsible for autoregulation of GFR

A

kidneys can maintain constant blood flow into glomerular capillaries despite changes in driving arterial pressure by altering arteriolar caliber > adjust resistance

if GFR increase as direct result of increase in arterial pressure, net filtration pressure and GFR can be decreased by constriction of afferent arteriole

17
Q

mechanisms contributing to auto regulation of GFR

A

myogenic mechanism and tubuglomerular feedback

18
Q

what is myogenic mechanism

A

arteriolar vascular smooth muscle stretches due to increase in pressure in vessel > smooth muscle contracts and afferent arteriole constricts > limit blood flow into glomerulus despite increasing arteriole driving pressure

19
Q

what is tubuglomerular feedback

A

smooth muscle cells within walls of afferent arteriole specialised to form granulose cells > collectively known as macula densa > detect changes in Na+ levels of fluid flowing past them

when GFR increase > more fluid flow through distal tube > increase in salt level > macula densa cells release atp adenosine > cause afferent arteriole to constrict > reduce GFR

20
Q

what is the role of baroreceptor reflex in extrinsic control of GFR

A

decrease in blood pressure > detected by baroreceptors > afferent arteriole undergoes sympathetically induced vasoconstriction so that there will be more resistance and thus blood pressure will increase > decrease GFR and urine output > more H2O and salt conserved for body > restore plasma volume so that short term cardiovascular adjustments are not needed

21
Q

how is GFR influenced by changes in Kf

A

each tuff of glomerular capillaries held together by mesangial cells

sympathetic stimulation > mesangial cells contract > closes off portion of filtering capillaries > decrease SA for filtration > decrease kf > decrease GFR

22
Q

how much is sodium reabsorbed in each of the different tubules

A

proximal: 67%
loop of henle: 25%
distal and collecting ducts: 8%

23
Q

what are the 3 inputs for renin secretion

A

granulosa cells detect fall in BP

macula densa cells detect fall in Na+ in fluid flowing past the distal tubules

baroreceptor reflex detects fall in BP > increase sympathetic activity > stimulate granulosa cells to secrete more renin

24
Q

what is tubular maximum

A

each carrier is specific for the type of substance it can transport across plasma membrane > limited number of each carriers > Tm is the maximum amount of a substance that can be actively transported from tubular fluid in a given time > any quantity filtered beyond its Tm escapes into urine

only Na+ does not have Tm

25
Q

how to calculate filtered load of a substance

A

plasma conc x GFR of substance

26
Q

what is renal threshold

A

the plasma conc at which Tm of a particular substance is reached and substance starts appearing in urine

27
Q

how is Cl- reabsorbed

A

-vely charged Cl- passively reabsorbed down electrical gradient created by active reabsorption of +ve Na+

Cl- passes BTWN, not THROUGH tubular cells

amount of Cl- reabsorbed is determined by rate of active reabsorption of Na+

28
Q

how are the 2 types of aquaporins different

A

AQ1 in proximal is always open > high permeability

AQ2 in principal in distal parts of nephron regulated by vasopressin

29
Q

how is water reabsorbed

A

basolateral pump activity of extrusion of Na+ > [Na+] diminishes in tubular fluid and and tubular cells while it increases in lateral spaces > osmotic gradient formed induces passive net flow of H2O from lumen into lateral spaces > accumulation of fluid in lateral space > buildup of hydrostatic pressure > flush H2O out of lateral space into interstitial fluid and into peritubular capillaries

30
Q

what is the mechanism for K+ secretion

A

basolateral pump simultaneously transports Na+ into lateral space and K+ from peritubular capillary into tubular cell

increase in plasma [K+] stimulates adrenal cortex to secrete aldosterone > secretion and urinary excretion of excess K+

31
Q

what are the properties of the descending and ascending loop of henle

A

descending: highly permeable to H2O but does not reabsorb Na+

ascending: actively transports NaCl out of tubular lumen into surrounding interstitial fluid but is never permeable to H2O

32
Q

what is the mechanism of vasopressin

A

vasopressin binds to receptor on basolateral membrane of principal cell in distal/collecting tube > activates cAMP 2nd messenger pathways > promotes insertion of AQ2 into opposite luminal membrane > increase permeability > water enters tubular cell from tubular lumen

33
Q

what is osmotic and water diuresis

A

osmotic diuresis: involves increased excretion of both water and solute caused by excess ubreabsorbed solute in tubular fluid (occurs in untreated diabetes mellitus)

water diuresis: increased urinary output of water with little or no increase in excretion of solutes

BS1016 Physiology (8 decks)

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