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Renal Week 2 2017/18 > 10: Physiology 6 > Flashcards

10: Physiology 6 Flashcards

1
Q

The fluid which enters the Loop of Henle has a ___ osmolarity.

The fluid which leaves the Loop of Henle has a ___ osmolarity.

A

entering - low osmolarity

leaving - still a low osmolarity, but ADH sorts that in distal tubules and collecting duct

Tubular fluid becomes highly concentrated in the Loop of Henle to set up the cortico-medullary concentration gradient and then becomes less concentrated again as it leaves

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2
Q

What is the osmolarity of the interstitium of the renal cortex?

A

300 mosmol/L

same as most of the body

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3
Q

What is the concentration gradient going from the renal cortex to medulla?

A

Increasing

(300 - 1200 mosmol/L)

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4
Q

As fluid goes down the collecting ducts, the osmolarity of the interstitium around it (increases / decreases).

A

osmolarity increases

So the water from the fluid moves to the interstitium, increasing fluid osmolarity

Leading to the production of a low volume of hypertonic urine

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5
Q

Where do the distal tubules drain?

A

Collecting ducts

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6
Q

What occurs in the distal tubules and collecting ducts?

A

Water balance

Ion balance

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7
Q

What regulates the absorption of ions and water in the distal tubules and collecting ducts?

A

Hormones

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8
Q

What hormones regulate water and ion reabsorption in the distal tubules and collecting ducts?

A

ADH

Aldosterone

ANP

PTH

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9
Q

What does ADH cause?

A

Increased water reabsorption

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10
Q

What does aldosterone cause?

A

Increased SODIUM REABSORPTION

Increased K+ and H+ secretion

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11
Q

What does ANP cause?

A

Decreased sodium reabsorption

opposite of aldosterone

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12
Q

What affects the permeability of the distal tubules to water?

A

[ADH]

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13
Q

In the absence of ADH, the permeability of the distal tubules to water is ___.

A

low

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14
Q

How does the early distal tubule absorb ions?

A

Triple transporter

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15
Q

How does the late distal tubule reabsorb ions?

A

Action of ALDOSTERONE (Na+) and PTH (Ca2+)

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16
Q

In the basal state, how permeable is the early collecting duct to ions?

A

Impermeable

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17
Q

Which gland produces ADH?

A

Hypothalamus

stored and secreted by posterior pituitary

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18
Q

Which ion triggers __cytosis of peptide hormones from cells?

A

Ca2+ dependent exocytosis

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19
Q

What is the half life of ADH?

A

10 - 15 minutes

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20
Q

When is ADH released by the posterior pituitary?

A

Reduced blood volume e.g dehydration, haemorrhage, sepsis

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21
Q

Which vessels have ADH receptors?

Which type of receptor are they?

A

Distal tubules

Late collecting ducts

G-protein coupled receptors

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22
Q

What is produced by G-protein-coupled ADH receptors when they are activated?

What does this cause in the apical membrane of the distal tubule and late collecting duct?

A

Cyclic AMP

Opening of aquaporins

Reabsorption of water

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23
Q

What is ADH also known as?

A

Vasopressin

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24
Q

The movement of water through ___ of the distal tubules and late collecting duct creates what between the tubules and capillaries?

A

aquaporins

osmotic gradient

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25
Q

High levels of ADH lead to the production of ___ urine.

Low levels of ADH lead to the production of ___ urine.

A

hypertonic / concentrated

hypotonic / dilute

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26
Q

As water is reabsorbed, the osmolarity of tubular fluid ___.

A

increases

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27
Q

Is the ascending limb of the Loop of Henle permeable to water?

A

No

NaCl only

28
Q

In high concentrations of ADH, the distal tubules and collecting ducts are ___ to water.

A

permeable

29
Q

In low concentrations of ADH, the distal tubule and collecting ducts are ___ to water.

A

impermeable

30
Q

Why does fluid leaving the Loop of Henle always have a low osmolarity?

A

Corticomedullary concentration gradient, loses all its salt as it travels back up, reducing its osmolarity

Remember ascending limb is impermeable to water so osmosis INTO the ascending limb doesn’t occur to reduce the osmolarity

31
Q

What are the Loop of Henle and ADH’s roles in the production of hypertonic urine?

A

Loop of Henle creates corticomedullary concentration gradient, but tubular fluid LEAVES loop with a low osmolarity again (because of the gradient)

ADH then alters permeability to water to increase/decrease fluid’s osmolarity as it travels back down into medulla

Usually producing hypertonic urine

32
Q

Does ADH affect the reabsorption of salt?

A

No, water only

33
Q

Which part of the brain detects the water content of the blood?

A

Hypothalamus

34
Q

What changes does the hypothalamus trigger in response to dehydration?

A

Increased secretion of ADH

Increased sensation of thirst

35
Q

In which situations may a low blood water content cause the hypothalamus to increase ADH secretion and thirst?

A

Inadequate fluid intake

Haemorrhage

Profuse vomiting

Sepsis (leaky vessels)

36
Q

Hypovolaemia causes a decrease in systemic ___ ___, which is detected by ___ ___ in the left atrium.

What does this cause?

A

decreased systemic blood pressure

stretch receptors

Increased ADH production

37
Q

What genetic disease is caused by low ADH secretion or abnormal receptor response to ADH?

A

Diabetes inspidus

Low ADH secreiton - central DI

Resistance / abnormal receptors - nephrogenic DI

38
Q

What are the symptoms of diabetes insipidus?

A

Large volumes of dilute urine

Extreme thirst

39
Q

Apart from genetic causes, what may cause central diabetes insipidus?

A

Pituitary problems

e.g tumour, haemorrhage

40
Q

How is diabetes insipidus treated?

A

ADH replacement

Desmopressin

41
Q

What drug can cause diabetes insipidus?

Which type of the disease?

A

Lithium

Nephrogenic diabetes insipidus

42
Q

Which two receptors can detect the conditions which trigger ADH secretion?

A

Osmoreceptors in the hypothalamus - detect decreased [water]blood

Stretch receptors in the atria - detect decreased atrial stretch

43
Q

Which type of receptors are found in the GI tract and inhibit ADH secretion in response to ingestion of fluid?

What type of mechanism is this?

A

Stretch receptors

Feedforward mechanism - because the change is happening in anticipation of increased [water]blood

44
Q

Which substance inhibits ADH secretion?

A

Alcohol

45
Q

What happens to fluid osmolarity in the

a) proximal tubules
b) descending Loop of Henle
c) ascending Loop of Henle
d) distal tubules and collecting ducts with high ADH levels
e) “” with low ADH levels

A

a) Stays the same (water and salt reabsorption at same rate)

b) Increases

c) Decreases back to 300 mosmol/L

d) Increases (as water is being reabsorbed)

e) Decreases (as water isn’t reabsorbed and some salt will be reabsorbed)

46
Q

Where is aldosterone secreted?

A

Zona glomerulosa of adrenal cortex

47
Q

In what conditions is aldosterone secreted?

A

1. Decrease in [Na+], stimulating RAAS

2. Increase in [K+], directly stimulating cells

48
Q

What is the action of aldosterone?

A

Increases Na+ reabsorption

Increases K+ and H+ secretion

49
Q

What are the effects of aldosterone on

a) K+
b) Na+
c) H+?

A

a) Increases K+ secretion

b) Increases Na+ reabsorption

c) Increase H+ secretion

50
Q

Concentration of which ion is closely related to blood pressure?

A

Na+

51
Q

How does aldosterone increase blood pressure?

A

Increases Na+ reabsorption

Causing an increase in BP, because water follows sodium

52
Q

Where is most K+ reabsorbed?

A

Proximal tubules

90% of potassium

53
Q

Aldosterone is responsible for the absorption of what proportion of potassium?

A

10%

54
Q

What electrolyte changes cause aldosterone secretion?

A

Decrease in sodium (indirectly, by RAAS)

Increase in potassium

55
Q

Which substance acts on the adrenal cortex to cause the secretion of aldosterone in RAAS?

A

Angiotensin II

56
Q

How do

a) aldosterone
b) angiotensin II

increase blood pressure?

A

a) Increased Na+ reabsorption, vasoconstriction

b) Vasoconstriction, thirst

57
Q

Which conditions cause renin release by the granular cells of the juxtaglomerular apparatus?

A

Renal hypoperfusion (as in hypotension or renal artery stenosis)

Decrease in tubular NaCl concentration

Sympathetic stimulation

three different mechanisms

58
Q

Aldosterone increases the expression of which channels in the renal tubules?

A

Na+ transporter on apical membrane

NaKATPase on basolateral membrane

59
Q

Why does heart failure cause fluid retention and oedema?

A

Reduced renal perfusion

Increase in renin secretion

Increased reabsorption of Na+ and water

Increased blood volume (exacerbating heart failure)

60
Q

What hormone is held in heart muscle and is secreted when stretch of muscle increases?

What does it do?

Why might muscle stretch increase?

A

Atrial natriuretic peptide

Decreases Na+ reabsorption, increasing water loss, causing decrease in blood volume

Hypervolaemia (so corrects this)

61
Q

What are three effects of ANP?

A

Decreases Na+ reabsorption

VasoDILATION of afferent arterioles in glomeruli

Decreases sympathetic input

62
Q

What is micturation?

A

Urination

63
Q

Which reflex causes involuntary urination?

A

Micturation reflex

64
Q

What triggers the micturation reflex?

Which autonomic nerves are involved in the contraction of the detrusor muscle?

A

Stretch of bladder wall

Parasympathetic

65
Q

Can the micturation reflex be resisted?

A

Yes

66
Q

Increased atrial stretch causes the secretion of which hormone?

A

ANP

67
Q

Decreased atrial stretch causes the secretion of which hormone?

A

ADH

Renal Week 2 2017/18 (11 decks)

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