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physiology Flashcards

1
Q

what is filtration?

A

process in kidney that occurs at glomeruli to form filtrate protein free

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2
Q

GFR?

AND VALUE?

A

180L/DAY = 125mls/min

measure of kidney function to regulate eco volume and eliminate waste/toxins

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3
Q

reabsorption is?

A

substances reabsorbed into blood and not to be excreted into urine

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4
Q

secretion is?

A

secreting substances into tubule and want to be excreted into thru urine

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5
Q

why are kidneys at high risk of vascular disease?

A

as high % of cardiac output used here - so vulnerable

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6
Q

efferent arterioles lead to ?

A

efferent arterioles lead to peritubular capillaries and then to renal vein

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7
Q

what forces are filtration dependant on? 2

A

hydrostatic forces - causing filtration

oncotic pressure forces - against filtration - but favour reabsorption

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8
Q

what other factors affect filtration?

A

molecule size
charge
shape

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9
Q

describe the normal afferent and efferent arterioles?

A

afferent - short and wide = low resistance

efferent - long and narrow = high resistance

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10
Q

why does only filtration occur at glomerular capillaries?

A

as hydrostatic pressure always exceeds oncotic pressure

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11
Q

hydrostatic pressure in glomeruli (Pgc) dependant on?

A

afferent and efferent arteriole diameter and balance between them

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12
Q

if contract afferent/efferent arterioles impact on filtration?

A

afferent contracted = decreased flow - decreased filtration

efferent contracted = lack of flow out - pressure in capillary increase and increased filtration

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13
Q

auto regulation of kidneys means?

A

kidneys are indepednat of nerves and hormones - can regulate GFR and blood flow themselves - can see it still in a isolated perfused kidney

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14
Q

percentage of plasma that is filtered?

A

20%

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15
Q

percentage of filtrate reabsorbed and secreted ?

A

19% reabsorbed and 1% excreted

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16
Q

forces needed for reabsorption and where?

A

oncotic pressure highest and hydrostatic pressure falls favouring reabsorption

in peri-tubular capillaries

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17
Q

reabsorption occurs where mainly in tubule?

A

primary convoluted tubule

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18
Q

tm?

A

maximum transport capacity of reabsorption - due to saturation of carriers

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19
Q

what happens if tm exceed?

A

excess substrate enters the urine - excreted

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20
Q

glucose filtering how much?

how much is reabsorbed?

A

freely filtered - all filtered

10mmoles/L - will be reabsorbed

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21
Q

normal glucose level?

A

5mmol/l

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22
Q

What does it mean when tm is set way above?

A

it means to ensure all nutrient is normally reabsorbed and maintains normal plasma conc.

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23
Q

how are Na ions reabsorption?
where?

and what is the result of this?

A

not by Tm mechanism - active transport instead
in proximal tubule

establishes a conc. gradient across tubule wall for other solutes to pass passively & use of carrier mediated transports

through use of Na active pumps

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24
Q

what ions diffuse passively across proximal tubule?

A

Cl- - negative ions

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25
Q

what drags/reabsorbs the rest of the permeable solutes across membrane?

A

water moves by osmosis and creates ongoing conc gradients - as it concentrates all the substances left in the tubule - creates conc. gradient

rest travel across by diffusion

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26
Q

how much urea is reabsorbed?

A

50% - reminder stays and most excreted

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27
Q

proximal tubule membrane impermeable to?

A

inulin and mannitol

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28
Q

normal ECF K level?

A

4mmoles/L

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29
Q

what happens to K in kidney? 3 things and where

A

filtered at glomerulus and reabsorbed at proximal tubule and secretion occur in distal tubule

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30
Q

aldosterone does what?

A

controls K secretion

Aldosterone increases =
increases K secretion in distal tubule
increases Na reabsorption in distal tubule

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31
Q

proximal tubule what occurs here?

A

reabsorption

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32
Q

what is the type of fluid leaving the proximal tubule?

A

isosmotic - 300 mOmoles/l

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33
Q

where are the proximal and distal tubules in the kidney?

A

in the cortex

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34
Q

where are the loop of Henle’s?

A

in the medulla

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35
Q

what is the minimum H2o loss? and why

A

500mls

required bc important for excretion of waste products

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36
Q

loop of Henle act as?

A

counter-current multipliers

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37
Q

explain ascending limb and descending limb of henle?

A

ascending limb - actively transports Na/cl out of tubule - impermeable to water - DILUTES

descending limb - freely permeable to water 0 impermeable to NACL - CONCENTRATES

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38
Q

what is the result of the ascending limb of the loop of henle?

A

conc falls in tubule
interstitium rises

horizontal gradient of 200mOsm made

producing hypotonic urine into distal tubule

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39
Q

role of the vasa recta ? 2

A

provide oxygen to medulla without disturbing gradient between interstitium and tubule

and removes volume from the interstiitum

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40
Q

where is the site of water regulation? controlled by?

A

in collecting duct where permeability is controlled by ADH

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41
Q

ADH released where?

made by what?

A

from posterior pituitary gland
made by SO and PVN in hypothalamus
stored in posterior pituitary and then released

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42
Q

adh relationship with water in body?

A

adh increase when decrease water in body - to preserve water in body and higher osmolarity
makes you pee more conc urine

when dehyrdrated -

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43
Q

adh and tonicity or osmolarity relationship ?

A

ONLY an increase in osmolarity that also increases tonicity is effective in causing an increase in ADH

toncitiy referring to solutes that are impermeable

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44
Q

is urea permeable?

A

yes - so doesn’t affect tonicity

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45
Q

the amount of urine to excrete depends on what? 2

A

adh

amount of solute to be excreted - as water needed to excrete it out !

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46
Q

how is the permeability of the collecting duct altered?

A

by incorporating water channels into the membrane - aquaporins - water pores in membrane

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47
Q

adh present means what type of urine?

what state is the body in then?

A

decrease volume of urine
increased conc of urine

dehydration

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48
Q

where is urea reabsorbed in cd ?

A

near medullary tips - permeable to urea here

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49
Q

adh and urea relationship?

A

adh makes medullary cd membrane more permeable to urea - so less urea in urine

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50
Q

anti-diuresis means?

A

dehydration state - to preserve water - reduced urine

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51
Q

ecf volume and adh relationship?

A

ecf volume of plasma in vessels goes up

adh down

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52
Q

ecf volume detected by what? 3

A

carotid and aortic baroreceptors
AND
atrial stretch receptor

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53
Q

what’s the most important role of the kidney?

A

regulation of volume

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54
Q

regulation of ecf means regulation of what too?

A

regulation of Na levels

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55
Q

affect of lowering ecf volume?

give examples of the above where it can happen

A

vomiting, diarrhoea

decreases in plasma volume - decreases in plasma pressure - leading to decrease in blood pressure - detected by atrial and carotid sinus baroreceptors - can restrict vessels AND INCREASE ADH

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56
Q

how does reabsorptive range in proximal tubule?

A

due to changes in reabsorptive forces -
oncotic pressure
and hydrostatic pressure

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57
Q

reabsorption during hypovalemia? DUE TO

A

is more than normal

ONCOTIC higher than normal
hydrostatic lower than normal

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58
Q

what is the forces in the proximal tubule in normovolaemia?

A

Ppc - is less
oncotic - larger
favours reabsorption in normal conditions

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59
Q

regulation of distal Na reabsorption is by?

A

aldosterone

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60
Q

juxtaglomerular cells explain what?

A

granule cells - smooth muscle around afferent arteriole - before entering glomerulus

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61
Q

macula densa?

A

loop of distal tubule

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62
Q

what is the juxtaglomerular apparatus?

A

JG cells + macula dense in distal tubule

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63
Q

JG cells make?

A

renin

64
Q

how much angiotensin II available is relied on what?

A

on how much renin there is

65
Q

angiotensin I role?

A

inactive and no role - mostly always converted to ANG II due to always present ACE enzyme

66
Q

aldosterone secretion triggered by?

A

angiotensin II

67
Q

what is the rate limiting step?

A

release of renin

68
Q

sympathetic activity - how does it cause increase in renin release?

A

via beta1 effect

69
Q

how does macula dense communicate with afferent arteriole? and result of it

A

when flow past the macula densa increases - is sends paracrine signalling TO afferent arteriole - it then constricts and pressure decreases in glomerulus - and GFR decreases

70
Q

volume or osmolarity to fix - what does the body do?

A

volume considerations have more importance - and is more key to maintain -

71
Q

ANP does what?

A

it promotes Na excretion -

works against aldosterone

72
Q

aldosterone affect on weight and why?

A

aldosterone increases Na reabsorption and water retention

this leads to weight gain

73
Q

ANP release triggered by? 3

leads to?

A

aldosterone leads to ANP release
also triggered by volume expansion and weight gain
and increase in blood volume and bp

natriuresis - Na loss and h2o in urine

still K depleted

74
Q

uncontrolled Diabetes leads to ?

A

hyperglycaemia coma = osmotic diuresis

75
Q

explain the mechanism of uncontrolled DM?

A
  • glucose levels in plasma exceed the TM and stay in proximal tubule

=and exerts an osmotic effect to retain water in tubule too

  • Na reabsorption is decreased and so therefore symport glucose reabsorption is further decreased

= resulting in fluid that is very dilute - very dilute fluid entering ascending limb

  • gradient in ascending limb is much less and EVENTUALLY LOST
  • higher volume of water deliver to distal tubule
  • this increase is detected by the macula densa AND detects the high rate of delivery of NaCl
  • renin secretion is reduced and Na reabsorption in distal tube is reduced
  • due to wrecked gradient - loose ability to conc. the urine - ADH loses ability to conserve
  • excrete 8L of ISOTONIC urine per day
76
Q

ascending limb of the loop involves what ions to be reabsorbed?

via what?

A

NaCl and POTASSIUM

vis the NaK Cl co transporter

77
Q

why must we regulate pH so much?

A

as enzymes reside here - so must keep highly regulated

78
Q

What contributes to the pH level?

A

number of free H+ ions

79
Q

2 types of acid?

A

respiritary acid and metabolic acid

80
Q

respiratory acid meaning?

A

increase ventilation
decrease in co2

lead to increase in carbonic acid

increase in H+ ions

81
Q

metabolic acids examples?

A

inorganic acids - phosphoric acids/amino acids

organic acids - fatty acids/lactic acids

82
Q

major source of alkali?

A

organic anions - citrate

83
Q

what is the role of buffer?

A

to minimize changes in pH when H+ ions are added or removed

84
Q

what’s the most important buffer?

name other buffers

A

bicarbonate buffer

plasma proteins/dibasic phosphate

85
Q

HCO3- regulated by?

Pco2 - regulated by?

A

renal regulated -

respiratory regulated - ventilation

86
Q

movement of H+ in and out of cells explain?

this can lead to what?

A

must be accompanied by Cl- in red cells or exchanged for a cation K+

in acidosis leading to hyperkalaemia/electrolyte disturbances

87
Q

pH remains in normal range as long as?

A

as long as kidney and lungs are working normally

88
Q

what does kidney regulate and how?

A

regulate HCO3-

  • by reabsorbing filtered HCO3-
  • by generating new HCO3-

both depend on active H ion secretion from tube cells on lumen

89
Q

titratable acidity meaning?

explain what happens in process?

A

buffered by HPO4-
the amount of NaOH needed to titrate urine pH back to neutral for urine sample

generates new HCO3-
and excretes H+ ions
WHEN ACID LOAD ONLY
in distal tubule

90
Q

distal tubule titratable acidity occurs leads to what?

A

generation of new HCO3- and excretion of H+

resulting in increased conc of P04-

91
Q

what is ammonium excretion?

A

major adaptive response to an acid load - pH down

generates new HCO3-
excretes H+ ions

92
Q

carbonic anhydrase does what?

A

enzyme that catalyses conversion from carbonic acid dissociation into its ions - H+ AND BICARBONATE

93
Q

RENAL GLUTAMINASE does what?

A

enzyme that catalyses the conversion of glutamine AA into glutamate AND DURING PROCESS FORMS NH3

94
Q

AMMONIUM excretion occurs where? 2

and difference between 2 locations

A

occurs in distal tubule and proximal tubule cell

distal - NH4+ forms outside tubule cell

proximal - use of NH4+/nA+ EXCHANGER - where NH4+ forms within cells and pass out into lumen

95
Q

renal glutamine is what dependant?

explain relationship

A

pH dependant

pH falls AND RG increases in activity

96
Q

how long does it take for ammonium excretion to have its effect? and why?

A

takes 4-5 days to reach max effect - as requires an increase in protein synthesis of renal glutamine

and takes time to switch off too! for opposite situation - increased alkali

97
Q

respiratory acidosis results from?

response?

A

reduced ventilation and retention of CO2

increases Pco2
to allow pH to fall

to increase HCO3-

98
Q

causes of respiratory acidosis?

A

drugs that depress respiratory centres in brain

obstruction of airways -copd/bronchitis/asthma

99
Q

respiratory alkalosis results from?

response?

A

increased ventilation and co2 blow off

decreases pco2
to allow pH increases

to decrease HCO3-

100
Q

causes of respiratory alkalosis? 2

A

hyperventilation

altitude

101
Q

metabolic acidosis?

response?

A

ph fall and due to HCO3 fallen

need to decrease pCO2

102
Q

how is metabolic acidosis corrected?

explain process and referred as?

A

increasing ventilation - to decrease PCO2

increase in depth not rate
called KUSSMAUL BREATHING

103
Q

CAUSES OF METABOLIC ACIDOSIS? 3

A

increase H+ production - DKA

failure to excrete H+ - renal failure

loss of HCO3- - failure to reabsorb

104
Q

resp correction vs renal correction?

A

respiratory compensation - takes mins

renal compensation - longer and delayed as RG synthesis - 4-5days to reach max

105
Q

metabolic alkalosis?

response?

A

ph increase and H+ decrease

increase in HCO3-

response is to increase pCO2

106
Q

causes of metabolic alkalosis?

A

increase in H+ ion loss - vomit

increase in renal H+ loss

excess adminstration of HCO3-

big blood transfusion - contains chemical which converts into HCO3-

107
Q

an increase in PCo2 - difference in changes in pH in chronic/acute resp acidosis ?

AND WHY

A

smaller decrease in Ph in chronic respiratory acidosis then acute respiratory acidosis

due to it takes time for NH2 production to switch on and have affect

108
Q

why is it important to measure GFR? 2

A

if renal disease - need to see nephron destruction and function

if drugs - see if renal function - and excretion of drug occurring - or else toxicity!

109
Q

clearance means?

A

vol of plasma cleared out

110
Q

what is used for measuring clearance? and why

A

inulin - as freely filtered but neither reabsorbed or secreted

only measures filtration !

111
Q

normal gfr? 2

A

125mls/min

100mls/min/1.73m squared

112
Q

what substance is currently used for clearance/gfr measuring?

and what’s the formula

what type of measurement does this give?

A

creatinine

eGFR - 1/Pcr

it gives us a estimated GFR - not calculated/exact

113
Q

what factors affect creatinine in body? 3

A

muscle mass - more muscle more creatinine

dietary intake - vegetarians have less C

drugs

114
Q

glucose clearance is?

A

Zero as - ALL REABSORBED

115
Q

UREA CLEARANCE?

A

LESS THAN INULIN

as 50% is reabsorbed

116
Q

PAH CLEARANCE MEANS?

A

measure of all plasma flowing through kidney in given time - RENAL PLASMA FLOW

117
Q

how is PAH CLEARANCE TESTED? e.g.

A

e.g - pencilling used

freely filtered and then remaining in plasma is actively secreted into tubule again

clearance larger than inulin

118
Q

how do ureters enter bladder? and why

A

at oblique angle - prevent reflux of urine

119
Q

what type of muscle in bladder?

A

detrusor muscle - 3 bundles of muscle

120
Q

internal and external sphincter explain control and type of muscle?

A

internal - not true - smooth muscle - not self uncontrolled

external - true - voluntary controlled - skeletal muscle

121
Q

urethral vs ureter obstruction?

A

urethral - bilateral renal problems

ureter - unilateral renal problems

122
Q

urine production varies between what?

A

750ml - 2500mls

123
Q

micturition reflex means?

A

release of urine - peeing after bladder fills and then empties

124
Q

EUS relaxes means?

A

external sphincter opens - to allow pee out

125
Q

how to delay peeing? (hold it in)

A

done by descending pathway from brain - established by potty training

126
Q

what happens after urination in males and females?

A

males - all urine in urethra expelled by contractions of bulbocavernosus muscle

females - urine empties by gravity

127
Q

osmolarity?

A

conc. of solute in solution

128
Q

adh released in response to? 3

A

dehydration and increased osmolarity and decreased ECF volume

129
Q

PTH secretion stimulated by?

and actions?2

A

low plasma calcium levels - so then its increases calcium ion reabsorption to increases CA plasma conc.

increases phosphate excretion in urine - by decreasing phosphate reabsorption

130
Q

what determines ADH release?

A

changes in tonicity

131
Q

prolonged vomiting leads to what state?

A

metabolic alkalosis - loss of HCl from stomach

132
Q

hyperventilation and hypoventilation leads to what acid/base state?

A

hyper - respiratory alkalosis - breathing off co2

hypo - leads to respiratory acidosis - keeps co2 in blood

133
Q

altitude affect on acid/base state?

A

respiratory alkalosis - increased ventilation

134
Q

normal values of acid/base values? 3

A

ph - 7.4
bicarbonate - 24
PCO2 - 40mmHg / 5.3kPa

135
Q

narrowed afferent arteriole leads to?

A

less blood flow
less pressure in glomeruli
less gfr
VICE VERSA

136
Q

percentages of what is filtered/excreted/reabsorbed?

A

100 % enters afferent arteriole
20% filtered
more than 19% reabsorbed
less than 1% excreted

137
Q

pressures at glomeruli and RESULT?

A

hydrostatic MORE THAN oncotic

favours filtration

138
Q

pressures at peritublar capillaries and RESULT FAVOURS?

A

oncotic MORE THAN hydrostatic

favours reabsorption

139
Q

how do inuline and mannitol go over proximal tubule membrane?

A

impermeable

140
Q

what type of fluid is delivered to distal tubule?

A

hypotonic fluid - 100mOsmol/L

141
Q

role of adh?

A

stimulated when low level of h2o in the body AND HIGH OSMOLARITY/TONICTY

used to

aim to RESERVE H20 and preserve it in blood

142
Q

anti-diaeresis/

A

dehydration -

143
Q

Na REABSORPTION IN PROXIMAL AND dISTAL tubule controlled by?

reasons for this?

A

aldosterone

in hypervolaemia/hypovolaemia

144
Q

3 ways to increase in renin release?

2 ways to decrease renin release?

A

HYPOVOLAEMIA
increase in sympathetic activity
decrease in JG cells stretch
decrease of NaCl delivery to macula densa

angiotensin II negative feedback
increase ADH

145
Q

Aldosterone does what to Na and K?

A

increases K secretion in distal tubule

increase Na reabsorption in distal tubule

146
Q

hypoproteinemia affect on glomerular filtrate produced?

A

osmotic pressure exerted by plasma proteins is lower than normal - so filtration pressure increases and filtrate increased

147
Q

haematocrit?

A

ratio of rbc to total blood volume - % of rbc in blood

148
Q

does gfr change a lot based on arterial pressure?

A

NO DUE TO pressure auto regulation

149
Q

PTH effect on excretion proximal tubule?

A

increases phosphate excretion in urine and decreases the reabsorption of phosphate too

150
Q

HCO3 elevated as result to situation already means?

A

suggests disturbance has been going long enough for kidneys to compensate

151
Q

what drug can produce diuresis?

explain mechanism?

A

furosemide

block NacL removal out of ascending loop of henle
- removing gradient - producing LOTS OF isotonic urine

152
Q

diuresis mean?

A

lots of urine produced

153
Q

ANG II does what?

A

constrict of smooth muscle

constrict efferent vessel of glomerulus

154
Q

insulin and glucagon does what to secretion of somatostatin?

A

insulin decreases it

glucagon increases it

155
Q

what detects changes in NaCl and changes gfr based on that?

A

macula densa

URINARY (4 decks)

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