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SF3- EXAM 3 (Camelita) > Basic Tubular Transport Mechanisms > Flashcards

Basic Tubular Transport Mechanisms Flashcards

1
Q

When excretion is less than filtration…

A

Reabsorption= Filtration- Excretion

Filtration= GFR x Plasma concentration

Excretion= Urine concentration x Urine flow rate

NOTE: This means that there is no net secretion

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2
Q

When excretion is greater than filtration…

A

Secretion= Excretion- Filtration

Filtration= GFR X plasma concentration

Excretion= Urine concentration x Urine flow rate

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3
Q

Glucose transport maximum

A

NOTE: Some substances have a maximum rate of tubular transport due to saturation of carriers, limited ATP, etc

EX: Glucose, amino acids, phosphate, sulfate

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4
Q

_____________ is the tubular load at which transport maximum is exceeded in some nephrons.

A

Threshold

NOTE: This is not exactly the same as the transport maximum of the whole kidney becuase some nephrons have lower transport maximums than others

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5
Q

Changes in concentration in proximal tubule

A
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6
Q

Transport in thick ascending loop of Henle

A
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7
Q

Which loop diueretics inhibit the Na-K-2Cl transporter of the thick limb of the loop of henle?

A

Furosemide

Ethacrynic acid

Bumetanide

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8
Q

Which diuretics inhibit the Na-Cl channels of the early distal tubule?

A

Thiazide diueretics

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9
Q

Which component of the distale tubule is functionally simular to the thick ascending loop?

A

Early Distal Tubule

  • Not permeable to water
  • Active reabsorption of Na+, Cl-, K+, Mg++
  • Contains macula densa
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10
Q

What relationship do the early distal tubules, late distal tubules, and collecting duct have with water and urea, respectively?

A

Early distal tubule

  • Not permeable to water
  • Not very permeable to urea

Late distal tubule

  • Permeability to H2O depends on ADH
  • Not very permeable to urea

Collecting duct

  • Permeability to H2O depends on ADH
  • Not very permeable to urea
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11
Q

Which cells secrete K+?

A

Principle cells

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12
Q

Aldosterone antagonists

A

Spironolacone

Eplerenone

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13
Q

Na+ channel blockers

A

Amiloride

Triamterene

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14
Q

Normal renal tubular Na+ reabsorption

A
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15
Q

If water is reabsorbed to a greater extent thatn the solute, the solute will become _______ (more/less) concentrated in the tubule.

A

More

Ex: Creatinine, inulin

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16
Q

If water is reabsorbed to a lesser extent than the solute, the solute will become ________ (more/less) concentrated in the tubule.

A

Glucose, amino acids

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17
Q

Changes of concentration substances in the renal tubules

A
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18
Q

Which hormones regulate tubular reabsoption?

A

Aldosterion

Angiotensin II

ADH

ANF

PTH

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19
Q

Normal urine concentration

A

1.2

NOTE: It is important for tubular reabsorption to increase when GFR increases to maintain a normal urine concentration.

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20
Q

How is peritubular capillary reabsorption calculated?

A

Reabsorption= Net Reabsorption pressure x Kf

NOTE: An increase in peritubular oncotic pressure increases reabsorption, while an increase in peritubular hydrostatic pressure leads to decrease in reabsorption.

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21
Q

Which factors determine peritubular capillary hydrostatic pressure?

A
  • Arterial pressure- Directly related
  • Increase in afferent resistance- Indirectly related
  • Increase in efferent resistance- Indirectly related
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22
Q

What factors determine peritubular capillary colloid osmotic pressure?

A
  • Plasma protein
    • ​An increase in plasma protein concentration, leads to an increase in arterial oncotic pressure, which leads to an increase in peritubular capillary oncotic pressure
  • Filtration fraction
    • ​An increase filtration fraction leads to an increase in peritubular capillary oncotic pressure
23
Q

Factors that can influence peritubular capillary reabsorption

A
24
Q

What actions does aldosterone have on late distal, cortical and medullary collecting tubules?

A
  • Increases Na+ reabsorption- principal cells
  • Increases K+ secretion- principal cells
  • Increases H+ secretion- Intercalated cells
25
Q

Conn’s syndrome

A

Primary aldosteronism

  • Excess aldosterone
    • Na+ retention
    • Hypokalemia
    • Alkalosis
    • Hypertension
26
Q

Addison’s disease

A
  • Aldosterone deficiency
    • Na+ wasting
    • Hyperkalemia
    • Hypotension
27
Q

What factors increase aldosterone secretion?

A
  • Angiotensin II
  • Increased K+
  • Adrenocorticotrophic hormone (ACTH)
28
Q

Which factors decrease aldosterone secretion?

A
  • Atrial natrueretic factor
  • Increased Na+ concentration

NOTE: ANP increases glomerular filtration rate and glomerular permeability. ANP also inhibits the effect of aldosterone on the mesangial cells.

29
Q

How does aldosterone function to increase Na+ and water reabsorption?

A
  • Stimulates aldosterone secretion
  • Directly increases Na+ reabsorption
  • Contricts efferent arterioles
    • Decreases peritubular capillary hydrostatic pressure
    • Increases filtration fraction, which increases pertubular colloid osmotic pressure
30
Q

ACE inhibitors

A

Captopril

Benazipril

Ramipril

31
Q

Angiotension II antagonists

A

Losartan

Candesartin

Irbesartan

32
Q

Renin inhibitors

A

Aliskirin

NOTE: Renin inhibitors decrease aldosterone, directly inhibit Na+ reabsorption, and decrease efferent arteriolar resistance

33
Q

ADH is secreted by _______

A

Posterior pituatary

NOTE: ADH is synthesized in the manocellular neurons of the hypothalamus

34
Q

Mechanism of action of ADH in distal and collecting tubules

A
35
Q

Feedback control of extracellular fluid osmolarity by ADH

A
36
Q

Excess ADH secretion can lead to ..

A

Decreased plasma osmolarity

Hyponatremia

37
Q

What condition can lead to insufficient release of ADH?

A

“Central” Diabetes Insipidus

  • Increased plamsa osmolarity
  • Hypernatremia
  • Excess thirst
38
Q

How does atrial natriuretic peptide increase Na+ excretion?

A
  • Secreted by cardiac atria in response to stretch (increased blood volume)
  • Directly inhibits Na+ reabsorption
  • Inhibits renin release and aldosterone formation
  • Increases GFR
  • Helps to minimize blood volume expansion
39
Q

PTH action on Ca++

A
  • Increases Ca++ reabsorption by kidneys
  • Increases Ca++ reabsorption by gut
  • Decrease phosphate reabsorption
  • Helps to increase extracellular Ca++

NOTE: PTH is released by parathyroids in response to decreased extracellular Ca++

40
Q

How does the sympathetic nervous system increase Na+ reabsorption?

A
  • Directly stimulates Na+ reabsorpion
  • Stimulates renin release
  • Decreases GFR and renal blood flow
    • Only at high levels of sympathetic stimulation
41
Q

How does increased arterial pressure decrease Na+ reabsorption?

A
  • Increase peritubular capillary hydrostatic pressure
  • Decreased renin and aldosterone
  • Increased release of intrarenal natriuretic factors
    • Prostaglandins
    • EDRF
42
Q

What effect does osmosis have on reabsorption?

A
  • Increasing the amount of unreabsorbed solutes in the tubules decreases water reabsorption
    • Diabetes mellitus
      • ​Unreabsorbed glucose in the tubules causes diueresis and water loss
    • Osmotic diuretics (mannitol)

NOTE: Water is reabsorbed only by osmosis

43
Q

Conn’s syndrome

A

Primary aldosterone excess

44
Q

Glucocorticoid remediable aldosteronism

A

Excess aldosterone secretion due to abnormal contraol of aldosterione synthase by ACTH (genetic)

45
Q

Renin secreting tumor

A

Excess Angiotensin II formation

46
Q

Inappropriate ADH syndrome

A

Excess ADH

47
Q

Liddle’s syndrome

A

Excess activity of amiloride sensitive Na+ channel (genetic)

48
Q

Diabetes Insipidus

A
  • Decreased water reabsorption
  • Hypernatremia
  • Nephrogenic
  • Lack of ADH
49
Q

Addison’s disease

A
  • Decreased Na+ reabsorption
  • Decreased K+ secretion
  • Lack of aldosterone
50
Q

Bartter’s syndrome

A
  • Decreased Na+, Ca++, HCO3- reabsorption
  • Hypotension
  • Decreased activity of Na-K-2Cl transporter in loop of Henle
    *
51
Q

Gitleman’s Syndrome

A
  • Decreased NaCl reabsorption
  • Hypotension
  • Decreased activity of NaCl co-transporter in distal tubule
52
Q

Fanconi syndrome

A
  • Generalized decrease in reabsorption
  • Often in proximal tubules
  • Causes:
    • Genetic
    • heavy metal damage
    • Drugs (tetracyclines)
    • Multiple myeloma
    • Tubular necrosis (ischemia)
53
Q

Renal tubular acidosis

A
  • Decreased H+ secretion
  • Increased HCO3- excretion
  • Acidosis
  • Causes:
    • Genetic
    • Renal injury
54
Q

Assessing Kidney Function

A

SF3- EXAM 3 (Camelita) (23 decks)

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