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Physiology > Urenal System > Flashcards

Urenal System Flashcards

0
Q

What is the functional unit of kidney?

A

nephron

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1
Q

What do the kidneys do?

A

1) maintain blood plasma volume therefore influencing the bp (MAP)
2) regulates ions and H2O
3) regulate acid-base balance
4) eliminates wastes, drugs, hormones
5) work with the endocrine system to release renin (for BP) and erythropoietin (rbc production)

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2
Q

What does the nephron contain?

A

renal corpuscle and tubule

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3
Q

What are the processes that happen in the nephron that lead to urine formation?

A

1) Glomerular Filtration
2) Tubular Resorption
3) Tubular Secretion

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4
Q

What percentage of plasma is filtered in the bowman’s capsule

A

20%

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5
Q

Filtration in the filtration membrane occurs via bulk flow due pressure. True or False

A

True

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6
Q

What does the filtration membrane consist of?

A

1) fenestrated endothelium aka glomerulus capillaries
2) podocytes with filtration slits in between
3) fused basement membranes

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7
Q

Describe the glomerulus filtrate

A
  • it is similar to plasma but without the large proteins
  • contains h2o, glucose, amino acids, vitamins, ions and urea and some SMALL proteins
  • pH level is around 7.45
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8
Q

What does glomerulus filtrate contain?

A

glucose, amino acids, water, vitamins, urea, ions, and small proteins

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9
Q

What is the pH level of glomerulus filtrate?

A

about 7.45

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10
Q

What are the different pressures influencing the net filtration pressure in the glomerulus?

A

1) Glomerular Hydrostatic Pressure
2) Blood Osmotic Pressure
3) Capsular Hydrostatic Pressure
4) Capsular Osmotic Pressure

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11
Q

What pressure promotes filtration?

A

glomerular hydrostatic pressure and capsular osmotic pressure

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12
Q

What pressure(s) opposes filtration in the glomerulus?

A

Blood osmotic pressure and capsular hydrostatic pressure

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13
Q

How do you calculate net filtration pressure

A

NFP = (GHP + COP) - (BOP + CHP)

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14
Q

The normal GHP is? (mmHg)

A

55 mmHg

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15
Q

The normal BOP is>

A

30 mmHg

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16
Q

The normal CHP is?

A

15 mmHg

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17
Q

The normal COP is?

A

0 mmHg

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18
Q

What is the normal NFP?

A

10 mmHg

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19
Q

The kidneys produce how much filtrate a day? what does this this mean about plasma volume

A

about 180 L/day meaning entire plasma volume is filtered about 65x in a day

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20
Q

How much filtrate is being produced by the kidneys in a minute

A

125 mL/min

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21
Q

What percentage of filtrate volume remains at the collecting duct for reabsorption?

A

less than 1%

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22
Q

why is it important to regulate GFR?

A

to keep GFR from changing when blood pressure changes

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23
Q

without GFR regulation, what happens to it when MAP increases

A

It increases as well

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24
Q

What are the intrinsic control to GFR?

A
  • myogenic mechanism

- juxtaglomerular apparatus

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25
Q

How does myogenic mechanism regulate GFR when MAP increases and decreases?

A
  • when MAP increases, the smooth muscle stretches which causes the afferent arteriole smooth muscle to contract which prevents glomerular blood pressure from increasing to
  • when MAP decreases, the afferent arteriole smooth muscle dilates and raises glomerular blood pressure
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26
Q

how does the juxtaglomerular apparatus regulate GFR when blood pressure decreases?

A
  • when blood pressure decreases, this causes the GFR to decrease which leads to low flow of filtrate past the macula densa
  • as a result, the macula densa releases local factors which dilates the afferent arterioles which increases GFR back to its resting rate
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27
Q

In terms of extrinsic control, how does the SNS regulate GFR?

A
  • it promotes vasoconstriction which causes decreases blood flow into the glomerulus via afferent arterioles and backs up blood in the glomerulus via efferent arterioles
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28
Q

in moderate SNS activation, does the GFR change?

A

not that much

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29
Q

In terms of extreme stress like heavy exercise and hemorrhage, what happens to GFR?

A

decreases

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30
Q

How does dehydration affect GFR?

A

it increases Blood Osmotic Pressure which decreases GFR

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31
Q

How do burns affect GFR?

A
  • it increases BOP which decreases GFR
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32
Q

How does urinary tract obstruction (eg. kidney stones) affect GFR?

A

it increases Capsular Hydrostatic Pressure which decreases GFR

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33
Q

How much of the filtrate is reabsorbed back to the blood

A

99%

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34
Q

During tubular reabsorption, filtrate travel from the tubule to ______ + _______

A

peritubular capillaries and vasa recta capillaries

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35
Q

Is tubular reabsorption passive or active?

A

both

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36
Q

When does an active process occur in tubular reabsorption?

A

when reabsorbing Na+, other ions, glucose and amino acids

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37
Q

When does passive process occur in tubular reabsorption?

A

when reabsorbing Cl-, urea and water

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38
Q

Is the proximal tubule regulated or not?

A

unregulated

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39
Q

What substances are 100% reabsorbed in the proximal convoluted tubule? Active or passive transport?

A

glucose and amino acids

- active

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40
Q

66% of this substance is reabsorbed in the proximal convoluted tubule via __________ transport.

A
  • NaCl

- active

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41
Q

are small proteins reabsorbed in the PCT? How?

A

yes through endocytosis small proteins become amino acids and travel to the blood

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42
Q

are vitamins reabsorbed in the PCT?

A

yes

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43
Q

Water is obligated to be reabsorbed in the PCT. True of False

A

True

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44
Q

If water is reabsorbed in the PCT obligatory, what does this mean?

A

it means that large amount of solute is removed and filtrate volume decreases

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45
Q

is filtrate isotonic, hypotonic or hypertonic to plasma?

A

isotonic

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46
Q

what is the unit of OP/L of filtrate to plasma?

A

300 mOsmoles/L

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47
Q

Overall, what is being reabsorbed in the proximal convoluted tubule?

A

glucose, amino acids, vitamins, water, NaCl, small proteins

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48
Q

In the loop of henle, the filtrate being reabsorbed goes to where?

A

vasa recta

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49
Q

In the loop of henle, what is being reabsorbed?

A

NaCl and water

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50
Q

Which limb facilitates water reabsorption?

A

descending limb

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51
Q

Which limb facilitates NaCl reabsorption?

A

ascending limb

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52
Q

Can water pass through the ascending limb?

A

no

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53
Q

Can NaCl pass through the descending limb?

A

no

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54
Q

Where is AT present, in the ascending or descending limbs of the loop of henle?

A

ascending

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55
Q

The descending and ascending limbs are part of what?

A

loop of henle

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56
Q

What is being reabsorbed in the distal convoluted tube?

A

Na, Cl-, Ca2+

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57
Q

Is water permeable in the early part of DCT?

A
  • no because of the absence of ADH
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58
Q

In the late DCT and collecting duct, what is being reabsorbed?

A

Na+ and water

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59
Q

Reabsorption of Na+ in the late DCT and collecting duct are facilitated by?

A

aldosterone

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60
Q

Is ANP (inhibits Na+ and water reabsorption) low or high?

A

low

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61
Q

What makes reabsorption of Na+ in the late DCT and collecting duct possible?

A

the low levels of ANP

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62
Q

Is water reabsorption in the late DCT and collecting duct regulated or unregulated?

A

regulated therefore it is facultative reabsorption

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63
Q

What makes water reabsorption possible in the late DCT and collecting duct?

A

increased ADH

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64
Q

nephrons usually reabsorb _______% of filtered H2O

A

99%

65
Q

nephrons usually reabsorb _______% of filtered NaCl

A

99.5%

66
Q

nephrons usually reabsorb _______% of filtered glucose

A

100%

67
Q

nephrons usually reabsorb _______% of filtered urea?

A

50%

68
Q

Will filtrate contain glucose or blood

A

no

69
Q

traces of _______ and ______ can possibly be seen in the filtrate.

A

amino acids and proteins

70
Q

Tubular secretion starts from _______ to the filtrate aka reverses of tubular reabsorption?

A

peritibular blood

71
Q

what substances are being secreted?

A

urea, K+, uric acid, some hormones, H+ and NH4+

72
Q

What makes secretion of K+ possible?

A

increased aldosterone levels

73
Q

Secretion of H+ and NH4+ maintain what?

A

blood plasma pH

74
Q

Countercurrent multiplication is for?

A
  • permitting excretion of urine that could be diluted or concentrated
  • producing and maintaining vertical osmotic gradient meaning there’s an increase of solutes as you move deeper into the medulla
75
Q

In terms of osmolarity urine ranges from?

A

100 mosmol/L (diluted) to 1200 mosmol/L

76
Q

In the countercurrent multiplication mechanism, what produces the vertical osmotic pressure?

A

the juxtamedullary nephrons

77
Q

Countercurrent mechanism happens because?

A

1) the descending limb of the loop of henle is permeable to water but impermeable to NaCl
2) the ascending limb of the loop of henle is permeable to NaCl but impermeable to water

78
Q

What pump exists in the ascending limb of loop of henle? What’s this for?

A

NaCl pump to pump out NaCl from the filtrate to the ISF

79
Q

Explain the process of countercurrent multiplication

A
  • as filtrate moves down the descending limb water moves to the ISF via osmosis since water is permeable here
  • this causes the filtrate to be more concentrated, and as it reaches the the ascending limb, the NaCl pumps out the solutes which are NaCl into to the ISF
  • The NaCl pump pumps solute against its concentration gradient with an osmolarity of 200 mosm/L` (low to high)
  • as filtrate moves up the early DCT, more NaCl are removed and water stays in the filtrate which causes an osmolarity of 100 mosm/L when it enters the late DCT
80
Q

What is the osmolarity of salt being pumped out by the NaCl pump?

A

200 mosmol/L

81
Q

What is the osmolarity of the filtrate leaving the ascending limb?

A

150 mosm/L

82
Q

Why is the osmolarity of filtrate leaving the ascending limb (150 mosm/L) lower than plasma?

A

because of the Ascending limb is impermeable to water and the existence of NaCl pump there

83
Q

what is the osmolarity of the filtrate as it moves to late DCT?

A

100 mosm/L

84
Q

why can urine be concentrated?

A

due to aldosterone which increases Na+ reabsorption

and ADH is increased which facilitates facultative water reabsorption in the late DCT and CD

85
Q

Concentrated urine can have an osmolarity as high as?

A

1200 mosm/L

86
Q

What causes diluted urine?

A

presence of ANP which inhibits ADP as a result, water reabsorption does not occur as well as NaCl

87
Q

When does concentrated urine occur?

A

dehydration and low blood pressure

88
Q

When does diluted urine occur?

A

when there is excess blood plasma and high blood pressure

89
Q

On average, how much urine is produced?

A

1 - 1.5 L/day

90
Q

What regulates urine?

A

1) Renin-angiotensin system
2) ADH
3) Aldosterone
4) SNS

91
Q

where does renin come from?

A

juxtaglomerular cells

92
Q

An increase in renin occurs when?

A

there’s a decrease in blood pressure or blood volume, a decrease in NaCl in the filtrate and an increase in SNS actvity

93
Q

the decrease of NaCl in the filtrate is detected by?

A

the macula densa

94
Q

A decrease in renin occurs when?

A
  • there’s an increase in blood pressure or volume, increase in ADH and angiotensin, and increase of NaCl in the filtrate.
95
Q

in details, explain the effect of increased renin

A

produces more angiotensin I that eventually becomes angiotensin II which stimulates 3 things:

1) the adrenal cortex which increases production of aldosterone which increases Na+ reabsorption and K+ secretion in the kidney which causes water to follow = concentrated urine
2) increased arteriolar vasonsontriction which causes increase systemic bp (MAP) and decreased GFR IF there’s a large decrease in blood pressure
3) the brain increases signals of thirst and and increases ADH which increases facultative reabsorption of water = concentrated urine

96
Q

Will an increase in renin causes concentrated urine or diluted urine?

A

concentrated

97
Q

Will a decline in renin cause concentrated urine or diluted urine?

A

diluted

98
Q

What does the hormone ADH do?/

A

increases facultative reabsorption of water in the late DCT and collecting duct

99
Q

An increase in ADH occurs when?

A

1) low blood pressure or volume
2) increased plasma osmolarity (because there’s low H2O)
3) increased angiotensin II
4) nicotine and nausea

100
Q

a decrease in ADH occurs when?

A
  • high blood pressure or volume
  • decreased plasma osmolarity
  • decreased angiotensin II
  • increased ANP
  • alcohol
101
Q

When does an increase of aldosterone occur?

A

increase in angiotensin II and K+ plasma concentraton

102
Q

What does the steroid hormone, aldosterone do?

A

it turns on the genes that increase number of Na+/K+ ATPase in DCT and CD which increases Na+ reabsorption followed by water via osmosis and then Cl-
and it also increases K+ secretion

103
Q

when does an increase in ANP occur?

A

an increase in blood pressure

104
Q

what does an increase in ANP do?

A

decreases renin which decreases angiotensin II which decreases aldosterone, ADH and decreases vasoconstriction which increases urine volume

105
Q

an increase in SNS causes what,

A

afferent and efferent arteriole vasoconstriction

106
Q

a decrease in SNS causes what?

A

technically it causes a decrease in vasoconstriction BUT myogenic response in the kidney is way more powerful thus overriding the effects of a decreased SNS impulse

107
Q

So when a decrease in SNS takes place, what happens?

A

MAP will still increase thus increasing blood flow to kidney which causes vasoconstriction inspite of the technical response of a decreased SNS impulse which is to decrease vasoconstriction (which is result of low SNS, low renin, angiotensin and increased ANP) and GFR returns to normal.

  • and because theres lack of ADH and aldosterone (since theres low renin) diluted urine will be produced which decreases blood volume (cause we will pee the urine out) which decreases MAP. Hormones corrects blood pressure which keeps GFR constant
108
Q

So when can the SNS really affect urine regulation?

A

when it causes a LARGE decrease in bp or volume

109
Q

Normal urine contains what?

A

1) water
2) nitrogenous wastes (eg. urea, uric acid, creatine)
3) regulated substances (eg. ions)

110
Q

What is the pH range of normal urine?

A

4.5 to 8

111
Q

what is the average pH level of urine?

A

6

112
Q

the presence of urea in urine is due to?

A

aa metabolism

113
Q

the presence of uric acid in the urine is due to?

A

nucleic acid breakdown

114
Q

creatinine in the urine is from?

A

break down of creatinine in skel. muscle

115
Q

what percentage of urea is taken away from the urine due to reabsorption?

A

50%

116
Q

What percentage of uric acid is reabsorbed (not present in urine)

A

10%

117
Q

is uric acid secreted in the nephron?

A

yes

118
Q

Is creatinine reabsorbed in the nephron?

A

no

119
Q

What causes creatinine to not be reabsorbed?

A

constant production and excretion

120
Q

Creatinine which is found in the urine is used for?

A

estimating GFR and can indicate kidney disease before symptoms occur

121
Q

How soluble is uric acid? What does this mean

A

very poorly soluble which means accumulation can happen which lead to gout (in joint) and kidney stones formation

122
Q

What does abnormal urine contain?

A

1) significant amount of proteins

2) glucose

123
Q

Presence of significant amount of proteins cause what?

A

proteinuria (aka albuminuria)

124
Q

What causes proteinuria (albuminuria)

A

1) increased permeability of glomerulus which is due to heavy metals and glomerulonephritis

125
Q

presence of glucose causes what?

A

1) temporary glycosuria

2) pathological glycosuria

126
Q

an example of temporary glycosuria is?

A

IV glucose

127
Q

An example of pathological glycosuria is?

A

diabetes mellitus which mens there’s high blood glucose (no insulin or receptors are not responding)

128
Q

What is micturition?

A

urinating

129
Q

Describe the flow of urine, in simple terms?

A

1) starts from the kidney which travels down the ureter
2) from there, it travels to the urinary bladder due to peristalsis and gravity
3) from there it goes to the urethra due to contraction of smooth muscle detrusor which produces pressure gradient

130
Q

In details what happens when urine reaches the bladder?

A
  • the stretch receptors send signals to:
    1) sacral spinal cord micturition centre - which stimulates the PSNS which causes detrusor sm muscle to contract internal urethral sphincter which contributes to expulsion of urine
    2) cortex which gives the “gotta pee feeling” and it either:
    • causes the external urethral sphincter to relax which contributes to urine expulsion or
    • causes “gotta wait” feeling which external urethral sphincter to not relax which causes urine hold back
      • BUT if bladder fills up pass 500 mL, external urethral sphincter relaxes and urine is expelled
131
Q

what is renal plasma clearance?

A

refers to the volume of plasma cleared of a substance in one minute

132
Q

What does plasma clearance estimate?

A

the time a substance remains in blood eg. drugs

133
Q

How do you calculate plasma clearance of a substance

A

PC of a substance “A” = volume of urine/min x volume of “a” in urine/volume of “A” in arterial plasma

134
Q

what can be used to estimate GFR in terms of plasma clearance?

A

inulin

135
Q

Why is inulin useful in determining GFR in terms of plasma clearance

A

because it is filtered but not reabsorbed, secreted or metabolized therefore the amount of inulin in the urine is the filtrate amount

136
Q

If PC of a substance is lower than the GFR aka plasma clearance of inulin (124 mL/min)what does this mean?

A

it means that the substance is reabsorbed from the filtrate

137
Q

what is the PC of urea?

A

about 75 mL/min

138
Q

what is the PC of glucose? what does this mean?

A

0 meaning it is 100% reabsorbed

139
Q

If PC of a substance is higher than the GFR aka plasma clearance of inulin (125 mL/min) what does this mean?

A

it means that the substance has been secreted into the filtrate

140
Q

which substance has a higher plasma clearance than GFR aka inulin plasma clearance?

A

penicillin and H+

141
Q

what is the acid-base balance?

A

regulation of free H+ in ECF

142
Q

H+ are normally produced by?

A

metabolism

143
Q

what is the normal body pH?

A

7.35 -7.45

144
Q

What does it mean when body pH is between 6.38 - 7.35?

A

acidosis

145
Q

What does it mean when body pH is between 7.45 - 8.0?

A

alkalosis

146
Q

What does it mean when pH is at 0 or 14?

A

death

147
Q

What prevents body pH from changing?

A

H+ is buffered

148
Q

buffered H+ is eliminated by?

A

respiratory system and renal system

149
Q

Chemical buffer systems are?

A

pairs of chemicals that work to prevent pH changes

150
Q

Describe the relationship of bases with H+?

A

they take up H+ meaning they remove H+ from solution

151
Q

Describe the relationship between acids and H+

A

they give up H+ meaning they add H+ to solution

152
Q

Balance of acids and bases mean?

A

minimized pH changes

153
Q

What is the main buffer system in the body?

A

bicarbonate buffer system

CO2 + H2O H2CO3(carbonic acid = acid) H+ +HCO3- (base)

154
Q

What are other buffers in the body?

A

1) Hb + H –> HbH in RBC

2) proteins in plasma and cells

155
Q

what is the buffer system in cells and plasma?

A

proteins

156
Q

What is the buffer system in the RBC?

A

HbH

157
Q

How does the respiratory system regulate pH levels?

A

Expulsion of CO2 due to rapid respiration causes decreased H+

158
Q

If too much H+ are removed, what happens?

A

hyperventilation (alkalosis)

159
Q

If too much H+ are retained, what happens?

A

hypoventilation —> acidosis

160
Q

Does the respiratory system work quickly as a buffer system?

A

yes

Physiology (11 decks)

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