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Renal > Physiology 4, 5 & 6 > Flashcards

Physiology 4, 5 & 6 Flashcards

1
Q

What is primary active transport?

A

Energy is directly required to operate the carrier and move the substrate against it’s concentration gradient.

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2
Q

Secondary active transport.

A

The carrier molecule is transported coupled to the concentration gradient of an ion (usually Na+)

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3
Q

Define facilitated diffusion.

A

Passive carrier-mediated transport ofa substance down it’s concentration gradient

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4
Q

What is the transport maximum?

A

Refers to a point where increases in concentration do not result in an increase in movement of a substance across a membrane.

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5
Q

What is the renal threshold?

A

The concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine

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6
Q

What is the renal threshold for glucose?

A

10-12mmol/l

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7
Q

How does sodium move acros the tubular epithelium?

A

By primary active transport throught the Na+/K+ ATPase pump at the basolateral membrane

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8
Q

What % of glucose in the filtrate is reabsorbed in the proximal tubule?

A

100%

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9
Q

What %s of salt, water and amino acids in the filtrate are reabsorbed in the proximal tubule?

A

salt - 67%
water - 67%
amino acids - 100%

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10
Q

The tubular fluid is what when it leaves the proximal convoluted tubule?

A

Iso-osmotic (300mosmol/l)

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11
Q

What is the function of the loop of Henle?

A

Generates a corticomedullary gradient which enables the formation of hypertonic urine

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12
Q

In terms of reabsorption of NaCl and water, what is the descending limb of Henle like?

A

Does not reabsorb NaCl

Highly permeable to water

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13
Q

In terms of reabsorption of NaCl and water, what is the ascending limb of Henle like?

A

NaCl is absorbed

Impermeable to water

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14
Q

The selective permeabilities of the ascending and descending limbs allows what to be established?

A

An osmotic gradient is established in the medulla

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15
Q

What is the maximum rtico-medullary gradient in humans?

A

1200

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16
Q

What is the purpose of countercurrent multiplication?

A

The conentrate the medullary interstitial fluid

To enable the kidney to produce urine of different volumes and concentrations according to the amount of circulating ADH

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17
Q

How does blood osmolality change as the vasa recta follows the loop of Henle?

A

Blood osmolality rises asit dips down into the medulla

Blood osmolality falls as it rises back up into the cortex

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18
Q

What mechanisms are in place to stop the vasa recta washing away the solute gradient?

A

Vasa recta capillaries follow hairpin loops
Vasa recta capillaries are freely permeable to NaCl and water
Blood flow to vasa recta is low (few juxtamedulary nephrons)

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19
Q

What 2 mechanisms make up the medullary osmotic gradient?

A

Countercurrent multiplier and urea cycle

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20
Q

The high medullary osmolarity of the loop of Henle allows what?

A

The production of hypertonic urine in the presence of ADH

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21
Q

The tubular fluid is what when it leaves the loop of Henle and enters the distal tubule?

A

Hypo-osmotic

100mosmol/l

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22
Q

How does the presence of ADH control water reabosrption?

A

Increases water reabsorption

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23
Q

What does the presence of aldosterone do?

A

Increases Na+ reabsorption

Increases H+/K+ secretion

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24
Q

ANP does what to Na+ reabsorption?

A

Decreases it

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25
Q

What are the effects of parathyroid hormone?

A

Ca2+ reabsorption increased

(PO4)3- reabsorption decreased

26
Q

The distal tubule has what permeabillity to water and rea?

A

Low permeability

Urea is concentrated in the tubular fluid of the distal tubule which increases the cortico-medullary gradient

27
Q

What happens in the early distal tubule?

A

Na+-K+-2Cl- transport (NaCl reabsorption)

28
Q

In the late distal tubule and early collecting duct what happens?

A

Ca2+ reabsorption
H+ secretion
Na+ reabsorption - basal state
K+ reabsorption - basal state

29
Q

The late collecting duct is permeable to what and what. What is it the main site of?

A

The late collecting duct is permeable to water and urea

Main site of ADH action

30
Q

Where is ADH synthesised and stored?

A

Synthesised - supraoptic and paraventricular nuclei in the hypothalamus
Stored - in granules in the posterior pituitary

31
Q

How does ADH increase the luminal permeabillity of the collecting duct to water?

A

By inserting new water channels (aquaporins)

32
Q

In the presence of maximal [ADH]plasma what kind of urine is produced?

A 
Small volume of concentrated urine 
Hypertonic urine (max 1400mosmol/l)
33
Q

In the presence of minimal [ADH]plasma what kind of urine is produced?

A 
Large volume of dilute urine 
Hypotonic urine (<50mosmol/l)
34
Q

Summarise the properties of the proximal tubule and descending loop of Henle.

A

Na+ reabsorbed by transcellular mechanisms (**PT only)
Water moves between inter-cellular junctions
These produce net fluid reabsorption
Na+ and water coupling

35
Q

Summarise the properties of the ascending loop of Henle and distal tubule.

A

Low water permeability of epithelium (ADH-dependent)
Na+ & Cl- reabsorption
These produce dilution of urine
Na+ & Cl- coupling

36
Q

Summarise the properties of the collecting duct.

A

Modulation of water / urea permeability

This contributes to determination of final urine osmolarity

37
Q

The distal tubule and collecting duct are the site of action of what?

A

Hormones - ADH, aldosterone, ANP

38
Q

What are the 2 stages of micturition?

A

Micturition reflex

Voluntary control

39
Q

What is the micturition reflex?

A

bladder can accommodate up to 250-400 ml of urine before stretch receptors initiate the micturition reflex. This reflex causes involuntary emptying of the bladder by simultaneous bladder contraction and opening of both the internal and external urethral sphincters.

40
Q

What is voluntary control when discussing urination?

A

Micturition can be voluntarily prevented by deliberate tightening of the external sphincter and surrounding pelvic diaphragm – up to a point.

41
Q

What are the basic functions of ADH, Aldosterone and ANP?

A

ADH - water balance
Aldosterone - Na+ reabsorption and K+ secretion
ANP - Na+ balance

42
Q

Why is the priority to regulate ECF osmolarity higher then that to regulate ECF volume?

A

The need for optimun [ion] and cell volume for cellular function
ECF volume is also regulated by CV reflexes

43
Q

What controls the release of ADH from the posterior pituitary gland?

A

Hypothalamus

44
Q

What stimulates and inhibits ADH secretion?

A

Stimulated by water deficit

Inhibited by water excess

45
Q

What is the most important stimulus for ADH secretion?

A

Hypothalamic osmoreceptors - detect and initiate the prioroy mechanism for regulation of ECF osmolarity - signal to ACH and thirst

46
Q

What exogenous compounds inhibit and stimulate ADH secretion?

A

Stimulate - Nicotine

Inhibits - Alcohol

47
Q

What alters the mount of Na+ reabsorbed and filtered?

A

Filtered - altered by regulation of GFR

Reabsorbed - regulated by RAAS

48
Q

What is aldosterone and where is it produced?

A

Steroid hormone

Produced by the adrenal cortex

49
Q

What is aldosterone secreted in response to?

A

Increased [K+]blood or decreased [Na+]blood

Activation of renin-angiotensin system

50
Q

What dos aldosterone do in terms of secretion and reabsorption of other ions? Be specific.

A

Stimulates Na+ reabsorption

Stimulates K+ secretion

51
Q

An increase in [K+]plasma does what to the adrenal cortex?

A

Directly stimulates it

52
Q

A decreased [Na+]plasma does what to the secretion of aldosterone?

A

Promotes the indirect secretion of aldosterone by means of the JGA (unknown mechanism)

53
Q

What 3 mechanisms help to control the renin release from granular cells of JGA?

A

decreased pressure in afferent arteriole
macula densa cells sense amount of NaCl in distal tubule and can control the release of renin to counteract this
Increased sympatehtic activity as a result of decreased arterial BP

54
Q

The granular cells of the JGA are directly innervated by..?

A

The sympathetic nervous system

55
Q

Does the presence of aldosterone increase or decrease the Na+ reabsorption in the DT and collecting duct?

A

Increases

56
Q

Problems with the RAAS can lead to what pathologies?

A

HTN

Fluid retention in congestive heart failure

57
Q

Where is Atrial Natriuretic peptide produced and stored?

A

Produced by the heart and stored in atrial muscle cells

58
Q

When is ANP released?

A

When the atrial muscle cells are mechanically stretched (increased circulating plasma volume)

59
Q

What is the function of ANP?

A

Promotes excretion of Na+ and diuresis (thus decreasing PV)

Alos exerts effet o CV system to decrease BP

60
Q

What is water diuresis?

A

Increased urine flow but not an increased solute excretion

61
Q

What is osmotic diuresis?

A

Increased urine flow as a reult of primary increased salt excretion

Renal (9 decks)

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