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Ps Renal System > L13 Renal System > Flashcards

L13 Renal System Flashcards

1
Q

Define diuresis

A

The removal of excess water in urine

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2
Q

What do diuretic drugs do?

A

Promote urine excretion
- formation of dilute urine

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3
Q

What do antidiuretic hormones control?

A

Controls the permeability of cells in the collecting duct to H2O

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4
Q

How do diuretic drugs work?

A

They make the collecting duct impermeable to H2O
- no reabsorption from the collecting duct

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5
Q

How does ADH regulate water volume?

A
  • ADH makes the collecting duct permeable to H2O
  • H2O is reabsorbed passively driven by the osmotic gradient in the medullary interstitium
  • results in concentrated urine and water conservation
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6
Q

Outline the mechanism of ADH

A

1) ADH bonds to receptors on the basolateral cell surface
2) stimulates adenylyl cyclase to generate cAMP and activate protein kinases
3) increased insertion of aquaporin 2 into apical membrane
4) increased water permeability
5) increased water reabsorption
6) concentrated urine water conservation

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7
Q

What controls ADH release?

A

Osmoreceptors

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8
Q

What can stimulate increased ADH release?

A

Decreased blood volume and pressure

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9
Q

Where is ADH produced?

A

By cells in the supraoptic and paraventricular nuclei of the hypothalamus

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10
Q

Where is ADH stored?

A

In vesicles in the posterior pituitary gland

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11
Q

What are changes in the plasma osmolarity sensed by?

A

By osmoreceptors in the hypothalamus

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12
Q

How does osmolarity affect ADH?

A

Increased osmolarity = increased ADH

Decreased osmolarity = decreased ADH

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13
Q

How is ADH removed?

A

By the liver and kidneys

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14
Q

How is normal osmolarity restored after water deprivation?

A
  • increased ECF osmolarity
  • supraoptic and paraventricular nuclei release ADH from the posterior pituitary
  • CD made water permeable
  • lateral pre optic area leads to thirst and the person drinks water to get back to normal osmolarity
  • water retention by the kidney
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15
Q

How is normal osmolarity restored after excessive fluid ingestion?

A
  • decreased ECF osmolarity
  • ADH release is suppressed and the CD is made water permeable via supraoptic and paraventricular nuclei
  • water excretion from the kidney
  • this suppressed by by the lateral pre optic area
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16
Q

List physiological stimuli for ADH release?

A

High temperature
Exercise
Pain
Heightened emotions/stress

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17
Q

How is nocturnal enuresis (bed wetting) caused?

A

There is a delay in development of the normal circadian rhythm of ADH
- increased ADH in adults overnight

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18
Q

What leads to innapropriate secretion of ADH?

A

Post operative pain
Intracranial disease
Ectopic ADH production - tumours
Pneumonia, TB, pulmonary disease

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19
Q

How does MDMA alter fluid balance?

A

when MDMA increases fluid in It stimulates
- thirst reflex
- repetitive behaviour

When MDMA decreases fluid out it stimulates
- ADH secretion

20
Q

What is the overall effect of ADH?

A

Decreased H2O excretion
Increase in blood volume

21
Q

What happens when there is a deficiency in ADH?

A

Diabetes insipidus

22
Q

What is caused when nephrons no longer respond to ADH?

A

Nephrogenic diabetes insipidus

23
Q

How are sodium ions handled by the nephron?

A

Freely filtered at the glomerulus
- 67% reabsorbed from PCT

None reabsorbed from the thin loop of henle
- 25% reabsorbed from thick ascending limb of LOH
- 5% reabsorbed from DCT
- 3% reabsorbed from collecting duct
- 0.4% of the filtered Na is excreted in dilute urine

24
Q

How can Na+ reabsorption be increased?

A

When the renin-angiotensin-aldosterone axis is activated

25
Q

How is renin release stimulated?

A

Decreased NaCl at macula dense
Stretch receptors in the afferent arteriole sense decreased BP
Increased renal sympathetic nerve stimulation due to central decreased BP

26
Q

What is the cellular action of aldosterone?

A

1) aldosterone binds to the receptor in the cytoplasm
2) initiates transcription
3) increased number of ENaC channels in apical surface
4) increased Na-K pumps
5) Na+ reabsorption where Cl- follows K+ secretion

27
Q

Where and when is aldosterone synthesised?

A

A steroid hormone synthesised in the adrenal cortex following stimulation by Angiotensin II

28
Q

What does aldosterone promote?

A

Promotes reabsorption of Na+ by principal cells in the last third of the distal convoluted tubule an in the cortical collecting duct

29
Q

What is the overall effect of aldosterone?

A

Decreased NaCl and H2O excretion
Increased blood volume

30
Q

What is the role of Angiotensin II?

A

Stimulates release of aldosterone from the adrenal cortex
Acts on the brain to create the sensation of thirst
Powerful vasoconstrictor

31
Q

What does Angiotensin II inhibit?

A

Inhibits the baroreceptor reflex and increases the release of norepinephrine from the sympathetic postganglionic fibres

32
Q

What is the overall effect of Angiotensin II?

A

Decreased NaCl and H2O excretions leads to increased blood volume and pressure

33
Q

How is atrial natriuretic peptide produced?

A

By the atria in response to stretch (increased BV/BP)

34
Q

What does atrial natriuretic peptide regulate?

A

Regulates the plasma volume and concentration of Na+

35
Q

What does ANP increase?

A

Increases renal water and Na+ excretion
- opposite actions to ADH and aldosterone

36
Q

What does ANP inhibit?

A

Inhibits thirst
Inhibits ADH, aldosterone and renin release

37
Q

What is the overall effect of ANP?

A

Increased NaCl and H2O excretion
Decreased blood volume and pressure

38
Q

What is nephrolithiasis?

A

The formation of renal calculi (kidney stones) crystalline structures which are composed of calcium oxalate salts

39
Q

What causes nephrolithiases?

A

Due to a higher than normal ion and solute concentration in the filtrate
E.g. dehydration, high fat/salt diets, obesity

40
Q

Where do crystals form in nephrolithiasis?

A

Form in the nephron loop, distal tubule and or collecting system

41
Q

Where do crystals travel?

A

They pass through the epithelium and can adhere to it

42
Q

What happens if crystals break off and lodge?

A

They can lodge in calyces, renal pelvis and ureter
Causes severe pain, blood in urine, sweating, nausea and vomitting

43
Q

Define urine

A

Fluid that leaves the collecting duct and flows through the ureter to the bladder

44
Q

Define bladder

A

A hollow organ that can expand to hold around 500ml
Has a smooth muscle wall
The neck of the bladder is continuous with the urethra

45
Q

What are the two rings on sphincter muscles?

A

Internal - smooth muscle that has normal tone which keeps it contracted

External - skeletal muscle controlled by somatic motor neurones and is kept contracted by tonic stimulation from the CNS

46
Q

Explain the structure of the bladder at rest

A

Internal sphincter passively contracted
External sphincter stays contracted
The bladder is in a relaxed filling state
Higher CNS input

47
Q

Outline the mechanism of micturition

A

1) stretch receptors fire
2) parasympathetic neurones fire and motor neurons stop firing
3) smooth muscle contracts and the internal sphincter passively pulls open
4) external sphincter relaxes

Ps Renal System (3 decks)

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