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1. Renal > Physiology of body fluid volume > Flashcards

Physiology of body fluid volume Flashcards

1
Q

What is the osmolarity of the fluid leaving the loop of henle? What does this make it?

A

100 mosmol

hyposmotic

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2
Q

What is the collecting duct bathed in?

A

progressively increasing concentrations of intersitial fluid as it descends through the medulla

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3
Q

Where does hormone regulation of fluid and NaCl affect?

A

distal tubule and collecting duct

>95% of the ions in filtrate have been reabsorbed before this though

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4
Q

What is the action of antidiuretic hormone?

A

increased water absorption

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5
Q

What is the action of aldosterone?

A

increased Na absorption and increased H/K secretion

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6
Q

What is the action of atrial natiuretic hormone?

A

decreased Na reabsorption

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7
Q

What is the action of parathyroid hormone?

A

increased Ca reabsorption

decreased phosphate reabsorption

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8
Q

What ions are transported in the early distal tubule?

A

Na, K and Cl

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9
Q

What ions are transported in the late distal tubule?

A

Ca, Na and K REABSORBED

H SECRETED

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10
Q

What are the characterisitics of the collecting duct in terms of water and ions?

A

early - permeable to ions

late - low ion permeability but high water and urea permeability

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11
Q

What type of hormone is ADH?

A

neuropeptide - synthesised by nerve cells

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12
Q

What happens when action potentials reach the ADH nerves?

A

ADH is released through Ca dependant exocytosis

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13
Q

What type of ADH receptors does the basolateral membrane express?

A

type 2

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14
Q

What happens when ADH binds to receptors?

A

cAMP increases which initiates the insertion of aquaporins (normally stored in vesicles) into the apical membranes of tubular cells

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15
Q

What does decreased ADH cause?

A

aquaporins become internalised

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16
Q

What is the purpose of aquaporins?

A

to create an equilibrium between the collecting duct fluid and tubular fluid

17
Q

Why would high volumes of urine come about due to the collecting duct?

A

in the collecting duct the membrane is impermeable to water so there is no water reabsorption

18
Q

Does ADH have an effect on salt reabsorption?

A

NO

19
Q

What does increased osmolarity trigger?

A

hypothalamic osmoreceptors -> hypothalamic neurons -> increased thirst

20
Q

What does decreased ECF volume trigger?

A

decreased arterial BP -> left atrial volume receptors activated -> hypothalamic neurones -> increased ADH and arterial vasodilation

21
Q

What are the two types of diabetes insipidus?

A

central - no ADH production

nephrogenic - produce ADH as normal but defect in Type 2 ADH receptors

22
Q

What stimulates ADH release?

A

nicotine

23
Q

What inhibits ADH release?

A

alcohol

24
Q

What does stimulation of stretch receptors in the upper GI tract cause?

A

feed forward initiation of ADH

25
Q

What is aldosterone secreted in response to?

A

increased K

decreased Na

26
Q

What is the role of aldosterone?

A

secrete K

reabsorb Na

27
Q

What would happen if there was no aldosterone?

A

tons of salt would be secreted from the body

28
Q

Should there be any K in the urine?

A

NO
90% of it is absorbed in proximal tubule
rest is absorbed in distal

29
Q

Where is angiotensin converting enzyme expressed?

A

outside of endothelial cells

30
Q

What 3 things stimulate renin release?

A
  1. reduced pressure in the efferent arteriole (low BP)
  2. low salt - sensed by macula densa cells
  3. increased sympathetic activity as a result of low BP - granular cells release renin and are innervated by sympathetic nervous system
31
Q

How does aldosterone increase the reabsorption of Na?

A

in the distal and collecting tubules, it increases the expression of sodium apical channels and basolateral sodium/potassium pump expression
this is done by change in gene expression and therefore

32
Q

What is atrial naturetic peptide?

A

released by the heart and stored in atrial muscle cells

33
Q

When is ANP released?

A

when atrial muscle cells are stretched due to an increase in circulating plasma volume

34
Q

What does ANP do?

A

promotes excretion of Na and diuresis - which decreases plasma volume and BP

35
Q

What are the two reflexes that control micturition?

A

micturation reflex (can hold 250-400ml before stretch receptors are triggered) and voluntary control (tightening of external spinchter and pelvic diaphragm)

1. Renal (28 decks)

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