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Physiology > BIOL 0800 Reading- Chapter 14 > Flashcards

BIOL 0800 Reading- Chapter 14 Flashcards

1
Q

Where does gluconeogenesis occur?

A

In the kidneys

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2
Q

What are the three main hormones/enzymes secreted by the kidneys?

A

Erythropoeitin, 1,25 dihydroxyvitamin D, and renin

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3
Q

What are the two components of the nephron?

A

Renal corpuscle and the tubule

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4
Q

What is the renal corpuscle?

A

The initial filtering component of the nephron: Bowman’s capsule and the glomerulus

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5
Q

What happens in the Bowman’s space?

A

Where protein-free fluid is filtered from the blood in the capillaries of the glomerulus

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6
Q

What is a podocyte?

A

The epithelial cells on the visceral layer of the Bowman’s capsule

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7
Q

What parts of the nephron are in the renal cortex vs medulla?

A

In the cortex: the renal corpuscles; in the medulla: varying lengths of the loops of Henle

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8
Q

What are peritubular capillaries?

A

The capillaries that run alongside the renal tubules

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9
Q

What is the blood flow through a nephron?

A

From afferent arteriole into glomerular capillaries into the efferent arteriole into the peritubular capillaries into the veins

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10
Q

What are the two types of nephrons?

A

Juxtamedullary and cortical

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11
Q

What are juxtamedullary nephrons?

A

Renal corpuscle is close to the cortical-medullary border, and tubule dips deep into the medulla: useful for reabsorption of water; lined by vasa recta

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12
Q

What is the vasa recta?

A

The long capillaries that line that juxtamedullary nephrons

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13
Q

Do all cortical nephrons have loops of Henle?

A

No: involved in reabsorption and secretion, but don’t contribute to hypertonic medullary interstitium

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14
Q

What is the juxtaglomerular apparatus?

A

Where the macular densa and JG cells combine between the afferent and efferent arterioles

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15
Q

What is the macula densa?

A

The patch of cells in the wall of the distal convoluted tubule

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16
Q

What are JG cells?

A

On the wall of the afferent arteriole; secrete renin

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17
Q

What is the formula for amount of substance excreted?

A

Amount filtered (in glomerulus) + amount secreted (in tubules) - amount reabsorbed (in tubules)

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18
Q

Why are proteins not included in the fluid filtered through the nephrons?

A

Because they’re too big, and because the filtration pathways in the corpuscular membranes are negatively charged and oppose plasma protein movements

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19
Q

Why aren’t plasma calcium and fatty acids filtered?

A

Because they’re usually bound to proteins in the plasma

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20
Q

What does glomerular capillary hydrostatic pressure favor?

A

Filtration of fluid out of the capillaries into Bowman’s space

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21
Q

What does the Bowman’s space hydrostatic pressure favor?

A

Opposition of filtration of fluid from capillaries into Bowman’s space

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22
Q

What does the osmotic force of the GC favor?

A

Opposition of filtration of fluid form capillaries into Bowman’s space; wants the fluid to stay in the GC

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23
Q

What does the osmotic force of Bowman’s space favor?

A

Nothing: there is no osmotic pressure in Bowman’s space because there aren’t any protein particles

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24
Q

What is the formula for net glomerular filtration pressure?

A

(P gc) - (P bs) - (pi gc)

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25
Q

What determines GFR?

A

Net filtration pressure, permeability of corpuscular membranes, and surface area available for filtration

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26
Q

How does afferent arteriole constriction affect GC hydrostatic pressure?

A

Decreases (P gc), decreases GFR

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27
Q

How does efferent arteriole constriction affect GC hydrostatic pressure?

A

Increases (P gc), increases GFR

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28
Q

How does mesangial cell activity affect GFR?

A

Contraction of mesangial cells (surround glomerular capillaries) reduces SA of capillaries; decreases GFR

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29
Q

What is filtered load?

A

The amount of any nonprotein/bound substance filtered into Bowman’s space: = (GFR)(concentration in plasma)

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30
Q

What are the two main methods of tubular reabsorption?

A

Diffusion and mediated transport

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31
Q

Tubular reabsorption by diffusion is dependent on reabsorption of what?

A

Water: reabsorption of water increases the concentration of the substance in the tubular lumen, causing it to diffuse into the peritubular capillaries

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32
Q

Mediated tubular reabsorption is often coupled to reabsorption of what substance?

A

Na+: sodium goes downhill, driving the uphill diffusion of other substances

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33
Q

What is the transport maximum?

A

The limit to the amount of material that can be transported per unite time by the mediated transport reabsorptive systems

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34
Q

What are the two most important substance secreted by tubules?

A

H+ and K+

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35
Q

Tubular secretion is usually coupled to reabsorption of what substance?

A

Na+

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36
Q

What part of the nephron is a big source of solute secretion?

A

Proximal tubule

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37
Q

What parts of the nephron are a big source of reabsorption?

A

Proximal tubule and loop of Henle

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38
Q

What is clearance?

A

The volume of plasma from which that substance is completely removed: Mass secreted per unit time / plasma concnetration

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39
Q

What is the formula for clearance?

A

(urine concentration of S)(volume of urine per unit time) / (plasma concentration of S)

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40
Q

What must occur if the clearance of any substance is greater than the GFR?

A

Substance must undergo tubular secretion: more volume has been cleared of substance than the volume that underwent filtration: something beyond filtration (secretion) is helping clearance

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41
Q

What is micturition?

A

Urination

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42
Q

What is the detrusor muscle?

A

Smooth muscle in the bladder that contracts to produce urination; stemmed by internal urethral sphincter and skeletal muscle of external urethral sphincter

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43
Q

What kind of neurons innervate the detrusor muscles?

A

Parasympathetic: causes contraction

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44
Q

What kind of neurons innervated the internal urethral sphincter muscles?

A

Sympathetic: causes contraction

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45
Q

What kind of neurons innervate the external urethral sphincter muscles?

A

Somatic: causes contraction

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46
Q

Why do Na+ and water have high reabsorption?

A

Because they easily filter due to low molecular weight and are unbound

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47
Q

Where is major hormonally-controlled reabsorption of Na+/water?

A

Distal convoluted tubules and collecting ducts

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48
Q

Where does the majority of Na+ and water reabsorption occur through bulk flow?

A

In the proximal tubule

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49
Q

What is a generalization about sodium reabsorption?

A

Active process; occurs in all tubular segments except descending Henle

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50
Q

What is a generalization about water reabsorption?

A

By osmosis; dependent on sodium reabsorption

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51
Q

Does transport of Na+ across the luminal membrane vary along tubule segments?

A

Yes: but transport across basolateral membrane doesn’t: still the active pump

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52
Q

Active Na+ reabsorption occurs on what membrane?

A

Basolateral membrane

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53
Q

What kind of channel makes membranes permeable to water?

A

Aquaporins

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54
Q

What is the water permeability of the proximal tubule?

A

Consistently high

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55
Q

What portion of the nephron is highly water permeable?

A

Proximal tubule

56
Q

What portion of the nephron has water permeability that is highly variable based on physiological control?

A

Cortical and medullary collecting ducts

57
Q

What hormone controls water reabsorption?

A

ADH: vasopressin

58
Q

What is vasopressin?

A

Peptide hormone, posterior pituitary

59
Q

What second messenger is involved in aquaporin fusion?

A

cAMP

60
Q

What protein kinase is involved in aquaporin fusion?

A

PKA

61
Q

What happens after vasopressin binds to basolateral membrane receptors?

A

cAMP triggers PKA to fuse AQP2 with the luminal membrane

62
Q

How does water passively reabsorb?

A

ADH triggers cAMP and PKA to fuse more AQP2 to the luminal membrane, and then it passes through AQP3 and AQP4 on the basolateral membrane

63
Q

What is water diuresis?

A

Increased urine excretion resulting from low ADH

64
Q

What is osmotic diuresis?

A

Increased urine flow as the result of a primary increase in solute excretion

65
Q

What causes diabetes insipidus?

A

Failure of posterior pituitary to release ADH or inability of kidneys to respond to ADH: low water permeability

66
Q

Where does urinary concentration take place?

A

Medullary collecting ducts

67
Q

How does medullary interstitial fluid compare to tubule fluid?

A

Hyperosmotic

68
Q

Why is medullary interstitial fluid hyperosmotic to the tubular fluid of medullary collecting ducts?

A

Countercurrent anatomy, NaCl reabsorption in the ascending Henle; water impermeability in ascending Henle; trapping urea in the medulla; hairpin vasa recta loops

69
Q

How does NaCl reabsorption occur along the upper and lower segments of the ascending Henle?

A

Lower: thin, simple diffusion; Upper: thick, active transport

70
Q

How permeable to water is the ascending Henle?

A

NOT: that’s why the interstitial medullary fluid is so hyperosmotic

71
Q

How permeable to water is the descending Henle?

A

Very, but not to solute!

72
Q

As tubular fluid passes through the distal convoluted tubule, how does osmolarity compare to the interstitial fluid?

A

Hypoosmolar

73
Q

The distal convoluted tubule: permeability to NaCl and water? Why is this important?

A

Actively permeable to NaCl, but not to water: makes fluid more hypoosmotic by allowing NaCl out, but keeping water in

74
Q

How does the vasa recta “hairpin” prevent the multiplier countercurrent effect from washing away?

A

Any diffusion that occurs in the descending hairpin is reversed by the ascending hairpin

75
Q

What is the equation for sodium in the renal system?

A

Na excreted = Na filtered - Na reabsorbed

76
Q

Are there receptors to detect Na+ changes?

A

No specific receptors, just the cardiovascular baroreceptors

77
Q

How can baroreceptors detect changes in Na+?

A

Since Na+ is a huge component of ECF solutes, changes in total-body sodium can cause changes in ECF volume, which also affects plasma volume

78
Q

What is the main direct cause of the reduced GFR?

A

Reduced net glomerular filtration pressure

79
Q

What is usually the cause of an increased GFR?

A

Increased neuroendocrine inputs when an increased total body sodium level increases plasma volume

80
Q

What is the major factor determining the rate of tubular sodium reabsorption?

A

Aldosterone

81
Q

Which was more effect on long term regulation of sodium excretion, GFR or Na reabsorption control?

A

Sodium reabsorption control

82
Q

Where is aldosterone produced?

A

Adrenal cortex; steroid hormone

83
Q

Where does aldosterone affect the nephrons?

A

Distal convoluted tubule and cortical collecting ducts

84
Q

What happens with high aldosterone to the sodium reabsorption?

A

Most sodium reaching the distal convoluted tubule and the coritcal collecting ducts Is reabsorbed

85
Q

Which acts more quickly, vasopressin or aldosterone?

A

Vasopressin because it’s a peptide, whereas aldosterone is a steroid: induces changes in gene expression and protein synthesis

86
Q

When can aldosterone become high?

A

When the person ingests a low-sodium diet or becomes sodium depleted

87
Q

What controls aldosterone secretion?

A

Angiotensin II: acts on the adrenal cortex to stimulate aldosterone secretion

88
Q

What is angiotensin II?

A

Component of renin-angiotensin system

89
Q

What is renin?

A

Enzyme secreted by JG cells of JG apparatuses in the kidneys

90
Q

What is angiotensinogen?

A

Produced by the liber; precursor to angiotensin I and II

91
Q

How does angiotensin I turn into angiotensin II?

A

By ACE: angiotensin converting enzyme

92
Q

Where is Ace found?

A

Luminal surface of capillary endothelial cells

93
Q

What are the most important effects of angiotensin II?

A

Stimulation of aldosterone secretion, constriction of arterioles

94
Q

What is the rate-limiting factor in angiotensin II formation?

A

Plasma concentration of renin

95
Q

What is the chain of events in salt depletion?

A

Increases renin secretion > increased plasma renin concentration > increased plasma angiotensin I > increased plasma angiotensin II> increased aldosterone release > increased plasma aldosterone

96
Q

What are the three distinct inputs to JG cells?

A

Renal sympathetic nerves, intrarenal baroreceptors, macula densa

97
Q

How do renal sympathetic nerves affect JG cells?

A

Directly innervate: increased activity stimulates renin secretion; reflexively activated by baroreceptors if low sodium/volume causes low blood pressure

98
Q

Why are JG cells intrarenal baroreceptors?

A

Because they’re located in the walls of the afferent arterioles and are sensitive to pressure: if BP decreases, cells stretched less and secret more renin

99
Q

Where is the macula densa located?

A

Near ends of the ascending loops of Henle

100
Q

What does the macula densa do?

A

Sense sodium concentration in tubular fluid; decreased salt releases paracrine factors to the JG cells: causes renin release

101
Q

How does the renin-angiotensin system balance arterial blood pressure?

A

Controlling Na reabsorption and thus blood volume; AND vasoconstriction

102
Q

What do ACE inhibitors do?

A

Reduce angiotensin II production: keep blood pressure lower

103
Q

What do angiotensin II receptor blockers do?

A

Prevent angiotensin II from binding to receptors on target tissues: vascular smooth muscle and adrenal cortex; treat hypertension

104
Q

What is ANP?

A

Atrial natriuretic peptide: secreted by atria; inhibit Na reabsorption; increase GFR for increased Na excretion

105
Q

When does ANP secretion increase?

A

Because of expansion of plasma volume that accompanies increased body sodium: increased atrial distension

106
Q

How does arterial pressure affect sodium reabsorption?

A

Increased arterial pressure inhibits Na reabsorption: increases Na excretion through pressure natriuresis

107
Q

What is the formula for water excretion?

A

Volume filtered through GFR MINUS volume reabsorbed

108
Q

Secretion of what hormone is the biggest determinant of total body water?

A

Vasopressin

109
Q

Why do changes in water excretion have little effect on extracellular volume?

A

Water distributes through all body fluid compartments, with two-thirds intracellular like NA

110
Q

What sensory receptors initiate reflexes controlling vasopressin secretion?

A

Osmoreceptors in the hypothalamus, when conditions are due to water gain or loss

111
Q

How does increased/decreased water ingested affect osmoreceptor firing and vasopressin secretion?

A

Increased water: decreased osmolarity, decreased firing, decreased vasopressin, increased water excretion; Decreased water: increased osmolarity, increased firing, increased vasopressin, decreased water excretion

112
Q

How do baroreceptors control water excretion?

A

Through receptors to vasopressinergic neurons in the hypothalamus; decreased pressure decreases baroreceptor firing: increases vasopressin secretion

113
Q

How does decreased ECF volume affect renin-angiotensin system and vasopressin secretion?

A

Decreased ECF causes increased aldosterone secretion from RAS, and increased vasopressin secretion

114
Q

How do alcohol and nausea affect vasopressin secretion?

A

Alcohol (inhibits vasopressin, increased water excretion); Nausea (stimulates vasopressin, decreased blood flow to GI)

115
Q

What brain area recognizes thirst?

A

Hypothalamus: triggers for thirst are similar to controls for vasopressin : osmoreceptors and baroreceptors in hypothalamus

116
Q

What is the most abundant intracellular ion?

A

Potassium

117
Q

True or false: K+ is freely filterable in the glomerulus

A

TRUE

118
Q

What part of the nephron can secrete K+?

A

Cortical collecting duct

119
Q

How is K+ secreted by the cortical collecting ducts?

A

Pumped into cell across basolateral membrane by NaK pumps (so associated with Na reabsorption)

120
Q

What is the most important factor for K+ secretion?

A

Increased K+ ingestion

121
Q

How does aldosterone affect K+ secretion?

A

Aldosterone stimulates K+ secretion from the cortical collecting ducts

122
Q

How does K+ concentration affect aldosterone secretion?

A

Directly: increase K+ stimulates adrenal cortex to product aldosterone to bring K+ concentration back down

123
Q

What controls calcium and phosphate balance?

A

PTH and 1,25 (OH)2D

124
Q

Where does most calcium reabsorption occur?

A

In the proximal tubule; very efficient because we NEED calcium

125
Q

How does PTH function in the kidneys?

A

In response to low calcium, opens calcium channels in the proximal tubule to increase reabsorption; also activates production of 1,25 (OH)2D to increase Ca and 1,25 (OH)2D reabsorption in the GI tract

126
Q

How does PTH affect phosphate ion reabsorption in the kidneys?

A

Decreases phosphate ion reabsorption in the proximal tubule

127
Q

What is the major extracellular buffer to control pH?

A

CO2/HCO3-

128
Q

What is the renal response to alkalosis?

A

Increased excretion of bicarbonate

129
Q

What is the renal response to acidosis?

A

Increased reabsorption/production of bicarbonate

130
Q

What is the formula for bicarbonate excretion?

A

Excreted = filtered + secreted - reabsorbed

131
Q

What does bicarb reabsorption depend on?

A

H+ secretion

132
Q

How does bicarb reabsorption occur?

A

Carbonic acid dissociates in the tubular epithelial cells; bicarb diffuses into interstitial fluid and H+ diffuses into lumen to recombine with filtered bicarb; filtered bicarb plus H+ reforms water and CO2 to eb reabsorbed; the original bicarb remains in the interstitial fluid

133
Q

How does the renal system produce extra HCO3- to respond to acidosis?

A

Secreted H+ combines with a buffer (HPO4–) into H2PO4-; this allows a net gain of bicarb into interstitial fluid

134
Q

How does ammonium secretion affect bicarb production for H+ secretion?

A

Tubular epithelial cells turn glutamine into NH4+ and bicarb; NH4+ actively secreted with a NH4+/Na+ pump; net gain of bicarb

135
Q

What is respiratory acidosis?

A

Respiratory system fails to eliminate CO2 as fast as it is produced

136
Q

What is respiratory alkalosis?

A

Respiratory system eliminates CO2 faster than it is produced

137
Q

What is metabolic acidosis/alkalosis?

A

Whenever it’s not respiratory

Physiology (13 decks)

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