Endocrine Control of Body Fluid Volume

Question 1

Where does the distal tubule end?

Answer 1

the collecting ducts

Question 2

How much of the ion loads are reabsorbed?

Answer 2

95%

Question 3

what is the estimated residual load of NaCl?

Answer 3

700-1000mmol NaCl/day

Question 4

What are the hormones that regulate ion and water balance?

Answer 4

ADH
Aldosterone
ANP
PTH

Question 5

What is the effect of ADH?

Answer 5

increased water absorption

Question 6

What is the effect of Aldosterone?

Answer 6

increase Na absorption

increase K/H secretion

Question 7

What is the effect of ANP?

Answer 7

decrease Na absorption

Question 8

What is the effect of PTH?

Answer 8

increase Ca absorption

decrease PO4

Question 9

What does the distal tubule have a low permeability to?

Answer 9

water and urea

Question 10

What does urea concentrated in the tubular fluid do?

Answer 10

establishes the osmotic gradient within the medulla

Question 11

What are the two segments to the distal tubule?

Answer 11

early and late

Question 12

What happens in the early distal tubule?

Answer 12

NKCC transport - Na Cl reabsorption

Question 13

What happens in the late distal tubule?

Answer 13

Ca reabsorption
H secretion
Na reabsorption
K reabsorption

Question 14

What is the collecting duct split into?

Answer 14

early and late

Question 15

What is the early duct similar to?

Answer 15

the late distal tubule

Question 16

What happens in late collecting duct?

Answer 16

a low ion permeability

permeability to water influenced by ADH

Question 17

When in ADH released?

Answer 17

when APs lead to Ca dependent exocytosis

Question 18

What is the half life of ADH?

Answer 18

10-15mins

Question 19

Where is ADH produced?

Answer 19

paraventricular nuclei in hypothalamus

Question 20

What does ADH do in the distal tubular cell?

Answer 20

increases permeability of the collecting duct by inserting aquaporins

Question 21

What is the effect of ADH on urine?

Answer 21

high water permeability = hypertonic urine 1400mosmol/l

Question 22

How does the tubular fluid equilibrate with the interstitium?

Answer 22

aquaporins

Question 23

What is true in the collecting duct?

Answer 23

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

Question 24

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

Answer 24

increase osmolarity

decrease volume

Question 25

What happens in water deficit?

Answer 25

hypothalamic osmoreceptors detect increase in osmolarity and decreased Arterial blood pressure

Question 26

What is diabetes insipidus or nephrogenic diabetes insipidus?

Answer 26

hereditary disease with large volumes of dilute urine and constant thirst

Question 27

What is the treatment for diabetes insipidus?

Answer 27

ADH replacement

Question 28

What are some stimulants and inhibitory influences of ADH?

Answer 28

nicotine stimulates

alcohol, stretch receptors in upper GI inhibits

Question 29

When is aldosterone secreted?

Answer 29

in response to rising K or falling Na in blood

activation of the renin-angiotensin system

Question 30

What does Aldosterone do?

Answer 30

Na reabsorption and K secretion

Question 31

Where is most K reabsorbed?

Answer 31

early regions of the nephron

Question 32

What happens to K when aldosterone is absent?

Answer 32

rest is reabsorbed in distal tubule

Question 33

What does an increase in K directly stimulate?

Answer 33

adrenal cortex

Question 34

How does a decrease in plasma Na promote indirect secretion of aldosterone?

Answer 34

the juxtaglomerular apparatus

Question 35

What does a decrease in NaCl, ECF and BP do?

Answer 35

stimulates release of renin from kidney which converts angiotensinogen to angiotensin I

Question 36

What converts Angiotensin I to angiotensin II?

Answer 36

angiotensin converting enzyme

Question 37

What does angiotensin II do?

Answer 37

stimulates adrenal cortex to produce aldosterone
stimulates thirst, ADH and arteriolar vasoconstriction
Na and Cl reabsorption

Question 38

What are the steps in renin release from granular cells in JGA?

Answer 38

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

Question 39

What can abnormal increases in RAA system?

Answer 39

hypertension

Question 40

What are abnormal increased in RAA responsible for in congestive heart failure?

Answer 40

fluid retention

failing heart causes decreased CO and BP -> low BP stimulates RAA -> increases salt and water retention -> failing heart

Question 41

What is the treatment for abnormal RAAS?

Answer 41

low salt diet, diuretics, ACE inhibitors

Question 42

What is ANP?

Answer 42

a hormone from atrial muscle cells that is released when the cells are mechanically stretched due to increase in plasma volume

Question 43

What does ANP promote?

Answer 43

excretion of Na and diuresis

Question 44

What is micturation?

Answer 44

urination

Question 45

What is urination governed by?

Answer 45

micturation reflex

voluntary control

Question 46

How much can the bladder store?

Answer 46

250-400ml before the stretch receptors activate the micturation reflex

Question 47

What does the micturation reflex do?

Answer 47

involuntary emptying of the bladder by simultaneous bladder contraction and opening of the internal and external urethral sphincters

Question 48

How can micturation be voluntarily prevented?

Answer 48

by deliberate tightening of external sphincter and surrounding pelvic diaphragm

Question 49

What stimulation causes the bladder to contract?

Answer 49

parasympathetic