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Endocrine System BDS1 > Control of Water and Electrolytes > Flashcards

Control of Water and Electrolytes Flashcards

1
Q

how do we gain water?

A

ingested water (food and drinks), water formed in metabolism

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2
Q

how do we lose water?

A

excretion: urine, faces, and evaporation: sweat, expired air

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3
Q

how much water do we take in and lose everyday?

A

2400ml on average

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4
Q

what control is urinary excretion under?

A

homeostatic control

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5
Q

what are the parts of the nephron?

A

glomerulus, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting ducts

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6
Q

what is the glomerulus involved in?

A

renal blood flow, filtration of plasma, glomerular filtration rate, filtration pressures

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7
Q

what is renal blood flow in ml/min

A

1200ml/min

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8
Q

what is glomerular filtration rate (GFR) in ml/min?

A

120ml/min

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9
Q

in the glomerular capillary whereabouts do the filtration pressures vary?

A

from the afferent arteriole to the efferent arteriole

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10
Q

what the capillary hydrostatic (blood) pressure in the glomerulus?

A

45-50mmHg

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11
Q

what is the plasma protein oncotic pressure in the glomerulus?

A

25-35mmHg

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12
Q

what is the capsular pressure in the glomerulus?

A

10mmHg

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13
Q

what is the net filtration pressure in the glomerulus?

A

10-15mmHg

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14
Q

what does the proximal convoluted tubule do?

A

obligatory reabsorption of 60-70% of the glomerular filtrate, secretion of hydrogen

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15
Q

what are absorbed in the proximal convoluted tubule?

A

ions, small organic molecules

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16
Q

what type of transport can be seen in the proximal convoluted tubule with regards to ion movement?

A

active transport; facilitated diffusion

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17
Q

what is the loop of henle important for?

A

concentration of urine (countercurrent exchange mechanism)

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18
Q

what does the concentration of urine depend on?

A

the active transport pumps in thick, ascending limbs of loop of Hnele

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19
Q

what does the length of the loop of Henle correlate with?

A

the ability to concentrate urine

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20
Q

what is the distal convoluted tubule involved in?

A

reabsorption of water, sodium, chlorine and calcium, and secretion of hydrogen and potassium

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21
Q

what is the activity of the distal convoluted tubule controlled by?

A

hormones

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22
Q

what hormones control the distal convoluted tubule?

A

aldosterone, atrial natriuretic hormone, ADH, parathyroid hormone

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23
Q

what are the collecting ducts responsible for?

A

water reabsorption

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24
Q

what influences water reabsorption?

A

ADH

25
Q

where does ADH go in the collecting ducts and for what purpose?

A

membrane channels for water reabsorption

26
Q

describe the movement of water in the collecting ducts

A

it moves along the osmotic gradients created by the counter current exchange mechanism

27
Q

what hormones control the regulation of water and electrolytes?

A

antidiuretic hormone, renin-angiotensin-aldosterone, atrial natriuretic hormone

28
Q

what is the main control of water?

A

ADH

29
Q

what is ADH also known as?

A

vasopressin

30
Q

where is ADH produced and released?

A

produced in the hypothalamus and released from posterior pituitary gland

31
Q

where does ADH act on to increase water permeability?

A

distal convoluted tubules and collecting ducts

32
Q

what helps ADH control water?

A

aquaporin channels

33
Q

what parts of the nephron does the water move between?

A

tubule lumen and interstitial fluid

34
Q

what triggers the release of ADH?

A

decreased plasma volume and increased plasma osmolarity

35
Q

what does decreased plasma volume do to the baroreceptor distension?

A

decreases it

36
Q

what does increased plasma osmolarity do to osmoreceptor activation?

A

increases it

37
Q

what does increased ADH release result in?

A

increased water permeability of collecting ducts

38
Q

what is ADH secretion increased by?

A

lower ECF volume (low pressure receptors in atria and great veins) and increased ECF osmolarity (osmoreceptors in hypothalamus)

39
Q

where are ions present

A

in the ICF and ECF

40
Q

what controls ions?

A

homeostatic control

41
Q

name the ions

A

sodium, potassium, hydrogen and calcium

42
Q

what organ does ion control operate through?

A

kidneys

43
Q

what controls sodium?

A

renin-angiotensin-alodsterone system and atrial natriuretic hormone

44
Q

what does the renin-angiotensin-aldosterone system do?

A

promotes reabsorption of Na (and water) in DCT in exchange for K and H

45
Q

what is angiotensin?

A

potent vasoconstrictor

46
Q

what does the atrial natriuretic hormone

A

increases excretion of Na (and water) and has the opposite effect to aldosterone

47
Q

describe the renin-angiotensin-aldosterone system

A

stimulus releases renin from juxta-glomerular apparatus - renin joins with angiotensinogen to make angiotensin I - angiotensin converting enzyme (ACE) acts on angiotensin I to make angiotensin II - angiotensin II travels to the adrenal cortex - increased aldosterone release - increased Na reabsorption in cortical collecting ducts

48
Q

what is the atria natriuretic hormone secretion pathway?

A

increased plasma volume - increased atrial distension - increased ANH release - increased glomerular filtration rate (GFR) and decreased sodium reabsorption - increased sodium excretion

49
Q

what do cell membrane potentials depend on?

A

ECF of potassium

50
Q

what is potassium regulated by?

A

aldosterone, Na is swapped for K or H

51
Q

what can hyposecretion of ADH result in?

A

diabetes insipidus - large volumes of insipid (tasteless) urine

52
Q

what is hyersecretion of ADH

A

syndrome of inappropriate ADH

53
Q

what does excess ADH lead to?

A

water retention

54
Q

what does increasing ECF of potassium do to nerve function?

A

depolarises, causing axons to fire axon potentials and remain in a refractory period

55
Q

why are potassium salts used in toothpastes?

A

to desensitise hypersensitive dentine

56
Q

how does the potassium salts in toothpaste work?

A

the ions diffuse along tubules and there is a raised potassium concentration at the inner end of the tubule, this depolarises the nerve, sodium channels are inactivated for a prolonged refractory period

57
Q

what is the problem with potassium salts in toothpase?

A

the potassium build up does not persist

58
Q

with regards to renal blood flow what events lead to the increased renin secretion from the juxta-glomerular apparatus?

A

decreased plasma volume - increased sympathetic nerve activity - decreased renal BF - decreased stretch of J-G baroreceptors - juxta-glomerular apparatus - renin secretion

59
Q

with regards to decreased glomerular filtration rate, what events lead to the increased renin secretion from the juxta-glomerular apparatus?

A

decreased plasma volume - increased sympathetic nerve activity - decreased renal BF - decreased GFR - decreased Na in tubular fluid - macula densa - juxta-glomerular apparatus - increased renin secretion

Endocrine System BDS1 (7 decks)

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