Endocrine Control of Body Fluid Volume Flashcards

1
Q

Where does the distal tubule end?

A

the collecting ducts

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2
Q

How much of the ion loads are reabsorbed?

A

95%

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3
Q

what is the estimated residual load of NaCl?

A

700-1000mmol NaCl/day

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4
Q

What are the hormones that regulate ion and water balance?

A

ADH
Aldosterone
ANP
PTH

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5
Q

What is the effect of ADH?

A

increased water absorption

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6
Q

What is the effect of Aldosterone?

A

increase Na absorption

increase K/H secretion

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7
Q

What is the effect of ANP?

A

decrease Na absorption

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8
Q

What is the effect of PTH?

A

increase Ca absorption

decrease PO4

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9
Q

What does the distal tubule have a low permeability to?

A

water and urea

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10
Q

What does urea concentrated in the tubular fluid do?

A

establishes the osmotic gradient within the medulla

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11
Q

What are the two segments to the distal tubule?

A

early and late

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12
Q

What happens in the early distal tubule?

A

NKCC transport - Na Cl reabsorption

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13
Q

What happens in the late distal tubule?

A

Ca reabsorption
H secretion
Na reabsorption
K reabsorption

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14
Q

What is the collecting duct split into?

A

early and late

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15
Q

What is the early duct similar to?

A

the late distal tubule

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16
Q

What happens in late collecting duct?

A

a low ion permeability

permeability to water influenced by ADH

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17
Q

When in ADH released?

A

when APs lead to Ca dependent exocytosis

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18
Q

What is the half life of ADH?

A

10-15mins

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19
Q

Where is ADH produced?

A

paraventricular nuclei in hypothalamus

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20
Q

What does ADH do in the distal tubular cell?

A

increases permeability of the collecting duct by inserting aquaporins

21
Q

What is the effect of ADH on urine?

A

high water permeability = hypertonic urine 1400mosmol/l

22
Q

How does the tubular fluid equilibrate with the interstitium?

A

aquaporins

23
Q

What is true in the collecting duct?

A

impermeable to water so no water reabsorption in presence of minimal ADH

24
Q

What does ADH do to urine osmolarity, volume and total solute excretion?

A

increase osmolarity

decrease volume

25
What happens in water deficit?
hypothalamic osmoreceptors detect increase in osmolarity and decreased Arterial blood pressure
26
What is diabetes insipidus or nephrogenic diabetes insipidus?
hereditary disease with large volumes of dilute urine and constant thirst
27
What is the treatment for diabetes insipidus?
ADH replacement
28
What are some stimulants and inhibitory influences of ADH?
nicotine stimulates | alcohol, stretch receptors in upper GI inhibits
29
When is aldosterone secreted?
in response to rising K or falling Na in blood | activation of the renin-angiotensin system
30
What does Aldosterone do?
Na reabsorption and K secretion
31
Where is most K reabsorbed?
early regions of the nephron
32
What happens to K when aldosterone is absent?
rest is reabsorbed in distal tubule
33
What does an increase in K directly stimulate?
adrenal cortex
34
How does a decrease in plasma Na promote indirect secretion of aldosterone?
the juxtaglomerular apparatus
35
What does a decrease in NaCl, ECF and BP do?
stimulates release of renin from kidney which converts angiotensinogen to angiotensin I
36
What converts Angiotensin I to angiotensin II?
angiotensin converting enzyme
37
What does angiotensin II do?
stimulates adrenal cortex to produce aldosterone stimulates thirst, ADH and arteriolar vasoconstriction Na and Cl reabsorption
38
What are the steps in renin release from granular cells in JGA?
reduced pressure in afferent arterioles - more renin macula densa cells sense the amount of NaCl in distal tubule - if reduced NaCl then renin released increased sympathetic activity as a result of reduced BP - causes renin release
39
What can abnormal increases in RAA system?
hypertension
40
What are abnormal increased in RAA responsible for in congestive heart failure?
fluid retention | failing heart causes decreased CO and BP -> low BP stimulates RAA -> increases salt and water retention -> failing heart
41
What is the treatment for abnormal RAAS?
low salt diet, diuretics, ACE inhibitors
42
What is ANP?
a hormone from atrial muscle cells that is released when the cells are mechanically stretched due to increase in plasma volume
43
What does ANP promote?
excretion of Na and diuresis
44
What is micturation?
urination
45
What is urination governed by?
micturation reflex | voluntary control
46
How much can the bladder store?
250-400ml before the stretch receptors activate the micturation reflex
47
What does the micturation reflex do?
involuntary emptying of the bladder by simultaneous bladder contraction and opening of the internal and external urethral sphincters
48
How can micturation be voluntarily prevented?
by deliberate tightening of external sphincter and surrounding pelvic diaphragm
49
What stimulation causes the bladder to contract?
parasympathetic