Physiology 6: endocrine control of body volume

Question 1

what is the osmolarity osmolarity of the filtrate when it reaches the distal convoluted tubule

Answer 1

100 mosmol/l (hypotonic)

Question 2

what is the osmolarity of the cortex vs the medulla

Answer 2

cortex isotonic and osmolarity increases towards the centre and becomes very hypertonic

Question 3

where do distal tubules empty into

Answer 3

collecting ducts

Question 4

what happens to urea in the distal tubule

Answer 4

becomes concentrated as low permeability

Question 5

what is reabsorbed in the early distal tubule

Answer 5

NaKCl co-transport and reabsorption

Question 6

what is reabsorbed and secreted in the late distal tubule

Answer 6

Ca reabsorption, Na and K reabsorption, H+ secretion

Question 7

what happens in the early collecting duct

Answer 7

similar to late distal tubule

Question 8

what happens in the late collecting duct

Answer 8

water permeable depending on ADH levels

Question 9

what affect does ADH have on kidneys

Answer 9

increases water reabsorption

Question 10

what type of peptide and hormone is ADH

Answer 10

octapeptide - neurohormone

Question 11

where is ADH synthesised

Answer 11

supraoptic and paraventricular nuclei in the HYPOTHALAMUS

Question 12

where is ADH stored

Answer 12

posterior pituitary

Question 13

how does dehydration trigger ADH release

Answer 13

increased plasma osmolarity is detected by hypothalamic osmoreceptors which triggers an AP to release ADH

Question 14

how does decreased atrial pressure trigger ADH release

Answer 14

stretch receptors in the left atrium detect low pressure and cause AP to release ADH

Question 15

what is the Half life of ADH

Answer 15

10-15 minutes

Question 16

what part of the nephron does ADH affect and how does it work

Answer 16

distal tubule/ collecting duct - uses ATP to insert water channels (aquaporins) into the lumen membrane

Question 17

what affect does nicotine have on ADH levels

Answer 17

stimulates ADH release

Question 18

what affect does alcohol have on ADH levels

Answer 18

inhibits ADH release

Question 19

what affect does high levels of ADH have on urine and vice versa

Answer 19

high ADH = high water permeability = hypertonic urine / low ADH = low water permeability = hypotonic urine

Question 20

what is central diabetes insipidus

Answer 20

damage to hypothalamus/ pituitary where ADH is not released

Question 21

what is nephrogenic diabetes insipidus

Answer 21

kidneys to not respond to ADH

Question 22

what are the symptoms of diabetes insipidus

Answer 22

large volumes of dilute urine + constant thirst

Question 23

what is the treatment for diabetes insipidus

Answer 23

nephrogenic: thiazide diuretics / central: ADH replacement

Question 24

what effect does aldosterone have on the kidneys

Answer 24

causes Na reabsorption and H/K secretion

Question 25

where is aldosterone secreted

Answer 25

adrenal cortex

Question 26

what can cause aldosterone to be released (3)

Answer 26

increased K in blood, decreased Na in blood, RAAS system

Question 27

where is K normally reabsorbed and how much is reabsorbed

Answer 27

proximal tubule - 90%

Question 28

what happens to K in the distal tubule when no aldosterone is released

Answer 28

rest is reabsorbed and no K is excreted in the urine

Question 29

how does increased [K]plasma directly stimulate aldosterone release

Answer 29

stimulates the adrenal cortex to secrete aldosterone

Question 30

how does decreased [Na]plasma indirectly stimulate aldosterone release

Answer 30

from the juxtogolmerular apparatus causing renin release

Question 31

what do the kidneys release renin in response to (3)

Answer 31

decreased NaCl / decreased ECF volume / decreased arterial BP

Question 32

what does renin do

Answer 32

converts angiotensinogen (liver) --> angiotensin I

Question 33

what does ACE do (lungs)

Answer 33

convert angiotensin I --> angiotensin II

Question 34

what does angiotensin II do

Answer 34

causes the release of aldosterone from the adrenal cortex

Question 35

what cells release renin

Answer 35

granular cells in the juxtaglomerular apparatus

Question 36

what 3 ways can renin be released by the kidneys

Answer 36

1) reduced pressure in afferent arteriole 2) macula densa senses reduced NaCl 3) increased sympathetic activity (from decreased BP detected by baroreceptors)

Question 37

what can an increased in the RAAS system causes

Answer 37

hypertension, fluid retention and congestive heart failure (and hypokalaemia)

Question 38

how can an overactive RAAS system be treated

Answer 38

low salt diet, loop diuretics and ACEi

Question 39

what effects does atrial natriuretic hormone (ANP) have on the kidneys

Answer 39

decreased Na reabsorption

Question 40

where is ANP produced and stored

Answer 40

produced in heart and stored in atrial muscle cells

Question 41

when is ANP released

Answer 41

when atrial muscle cells are stretched due to increased plasma volume (BP)

Question 42

how does ANP cause plasma volume decrease in the kidneys

Answer 42

by reducing Na reabsorption which causes diuresis which causes decreased plasma volume

Question 43

what effects does ANP have on the whole body to decrease BP (4)

Answer 43

reduced Na reabsorption / reduced renin production / vasodilation / reduced sympathetic activity

Question 44

what effects does Parathyroid hormone have on the kidneys

Answer 44

increased Ca reabsorption and decreased phosphate reabsorption

Question 45

what happens to filtrate (urine) once it leaves the kidneys

Answer 45

traveled down ureters by peristalsis to bladder for temporary storage and then micturition

Question 46

what happens in the first stage of micturition - the micturition reflex

Answer 46

bladder can hold 250-400ml of urine before stretch receptors initiate micturition and cause involuntary bladder contraction and opening of internal and external urethral sphincter (parasympathetics)

Question 47

what happens in the second stage of micturition - voluntary control.

Answer 47

deliberate tightening of external sphincter and pelvic diaphragm

Question 48

what is water diuresis

Answer 48

increased urine flow but no increased solute excretion

Question 49

what is osmotic diuresis

Answer 49

increased urine flow and increased solutes (usually Na) in urine