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Physiology > Renal 5 - Regulation of Tubular Reabsorption > Flashcards

Renal 5 - Regulation of Tubular Reabsorption Flashcards

1
Q

what is tubular reabsorption controlled by

A

local control mechanisms, nervous system and endocrine system

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2
Q

what are the local control mechanisms of tubular reabsorption

A

-tubuloglomerular feedback (TGF)
- glomerulotubular balance (GTB)
-pressure natriuresis/diuresis

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3
Q

what hormones control tubular reabsorption

A
  • aldosterone
    -ANG II
  • ADH
    -ANP
    -PTH
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4
Q

what division of the nervous system regulates tubular reabsorption

A

sympathetic nervous system

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5
Q

what does the TGF response do

A

autoregulation of GFR to keep it constant

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6
Q

what does the TGF response consist of

A

afferent and efferent arteriolar resistance related to flow rate of NaCl by macula densa

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7
Q

what does the GTB regulate

A

autoregulation of PT reabsorption rate related to tubular load

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8
Q

in GTB, as tubular load increases, the rate of reabsorption _____

A

increases

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9
Q

what does GTB depend on

A

changes in peritubular capillary and renal interstitial fluid starlings forces

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10
Q

what do TGF and GTB do together

A

prevent overloading of the distal tubule segment when GFR increases due to pressure changes or other disturbances
-assures homeostasis is maintained

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11
Q

what can small changes in MAP do to Na+ and water excretion

A

can cause large increases in their excretion

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12
Q

what do pressure natriuresis and pressure diuresis do

A

assure that large changes in salt and water intake only cause small changes in ECF volume, CO and MAP

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13
Q

what are the stimuli for aldosterone

A

-high [ANG II] in ECF
- high [K+] in ECF
- low blood pressure
- low Na+

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14
Q

what are the effector responses for aldosterone

A

-stimulates Na+ reabsorption
- stimulates K+ secretion
-increases H+ secretion by intercalated cells of late distal and cortical collecting tubule: excess aldosterone may cause metabolic acidosis
- increases Na+ reabsorption and K+ secretion by sweat and salivary glands
- increases Na+ absorption by intestine

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15
Q

what cells does aldosterone act on

A

principal cells

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16
Q

describe the response from aldosterone and why

A

slow onset long duration because it involves gene expression (slow onset) and circulates bound to plasma proteins so it lasts longer

17
Q

what would cause a decrease in aldosterone secretion

A
  • ANP via decreased renin secretion
  • increased Na+ concentration
  • high blood pressure
18
Q

what does ANG II do

A

major regulator of Na+ and water reabsorption

19
Q

what are the stimuli for renin secretion

A

-decreased MAP
- decreased ECF volume
- decreased filtrate flow rate to macula densa
- increased sympathetic activity

20
Q

what inhibits renin secretion

A

increased ANP

21
Q

where does ANG II action occur

A

in most nephron segments

22
Q

what are the effector responses for ANG II

A

-stimulates aldosterone production and secretion from zona glomerulosa
- directly increases Na+ reabsorption
- increases H+ secretion
- constricts efferent arterioles and increases GFR
- constricts systemic arterioles, increasing TPR and MAP

23
Q

what does ADH do

A

increases water reabsorption in the apical membrane in the late distal tubule and collecting duct

24
Q

what are factors that stimulate ADH secretion

A
  • increased ECF osmolarity
  • decreased blood volume via decreased ANP
  • decreased blood pressure via decreased baroreceptor activity
  • nausea
    -hypoxia
  • nicotine and morphine
    -ANG II
25
Q

what factors decrease ADH secretion

A
  • decreased ECF osmolarity
  • increased blood volume via increased ANP
  • increased BP via increased baroreceptor activity
  • ethanol
    -cold
26
Q

what are the mechanisms of action of ADH

A
  • increases water permeability via activation of Galpha s protein linked receptor
  • activates cAMP
    -increases the synthesis and insertion of AQP-2 into apical membrane
27
Q

what does ANP do

A

increases GFR and decreases Na+ reabsorption and increases Na+ excretion

28
Q

what is the stimulus for ANP

A

secreted by cardiac atria in response to stretch from increased blood volume

29
Q

what are the effector responses of ANP

A
  • directly inhibits Na+ and water reabsorption in PT
  • increases GFR by dilating afferent arterioles and constricting efferent arterioles
  • inhibits renin release and aldosterone formation
  • helps minimized blood volume expansion
30
Q

what does the sympathetic nervous system do in tubular reabsorption

A

-decreases Na+ and water excretion by:
-constricting arterioles
-stimulates renin release
-decreases GFR and renal blood flow
- directly stimulates Na+ reabsorption via alpha receptors on tubule epithelial cells in PT and TAL

31
Q

what is total body calcium and where is it stored and how much in each

A
  • 1100 g
  • 99% bones
  • 0.1% ECF
  • 1 % ICF
32
Q

what is Ca++ critical for

A

-normal cell function
- neural transmission
- membrane excitability
- bone structure
- blood coagulation
- intracellular signaling

33
Q

what form of calcium is most important for functions in the body

A

ionized

34
Q

describe the renal processing of Ca++

A

60% of plasma calcium filtered
- 65% of filtered calcium reabsorbed in PCT
- 25-30% reabsorbed in loop of henle
- 4-9% reabsorbed in distal and collecting tubule
-1% excreted

35
Q

where does PTH regulate Calcium in the nephron

A

in TAL and DT

36
Q

what mechanism does PTH affect calcium reabsorption

A

only transcellular

37
Q

what percentage of calcium is reabsorbed by transcellular and paracellular transport

A

50% each

38
Q

what promotes passive paracellular movement of calcium

A

the +8 mV luminal charge

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