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BIOM 3200 > Renal System > Flashcards

Renal System Flashcards

1
Q

Where are ADH and oxytocin produced?

A

In the cell bodies of the paraventricular and supraoptic nuclei of the hypothalamus

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2
Q

Where are ADH and oxytocin stored after their production?

A

In the posterior pituitary gland until released

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3
Q

What do osmoreceptors do?

A
  • Sense increased solute concentration/osmolality

- Signal PVN and SON to produce ADH

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4
Q

Where are osmoreceptors located?

A

Hypothalamus

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5
Q

What does ADH do?

A

Helps to increase water reabsorption in the kidneys so that water is retained by kidneys and returned to blood, not lost to urine

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6
Q

What is blood/plasma osmolality?

A

Measure of plasma [solute] including Na+, Cl-, K+, urea, glucose, etc.

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7
Q

What is the normal range of blood/plasma osmolality?

A

280-303 mOsm/kg

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8
Q

What affects osmolality?

A

Water content changes

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9
Q

What is special about Brattleboro rats? What is the result?

A
  • Do not produce ADH
  • Result of a naturally occurring mutation
  • Kidneys cannot retain water
  • Excessive thirst
  • Dilute urine
  • Diabetes insipidus (increases risk of seizures secondary to dehydration)
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10
Q

When does ADH typically increase?

A

During sleep to increase water reabsorption and decrease nocturnal urine production (Circadian pattern)

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11
Q

How can ADH production be related to kids who wet the bed?

A

They may underproduce ADH

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12
Q

What does body water content vary with?

A
  • Biological sex

- Age

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13
Q

What is the typical body water content for babies?

A

75%

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14
Q

What is the typical body water content for women?

A

50%

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15
Q

What is the typical body water content for men?

A

60%

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16
Q

What is the typical body water content for elderly men/women?

A

45%

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17
Q

How is water homeostasis maintained?

A

Water intake must equal water loss

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18
Q

What contributes to water intake?

A
  • Drinking fluid and water in food (most)

- Water produced by metabolism (little bit)

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19
Q

What contributes to water loss?

A
  • Urine (1500 mL)
  • Lungs (700 mL)
  • Sweat (200 mL)
  • Feces (100 mL)
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20
Q

What proportion of water is found intracellularly?

A

2/3

cytoplasm

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21
Q

What proportion of water is found extracellularly?

A

1/3

Interstitial fluid/blood plasma

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22
Q

What is the survival rule of 3s?

A

You can live…

  • 3 mins without air
  • 3 hrs in a harsh environment
  • 3 days without water
  • 3 weeks without food
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23
Q

What is the longest that people have survived without water?

A

8-10 days

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24
Q

How do Arabian camels regulate water?

A
  • Cannot shut kidney activity down
  • Lipid is stored in hump
  • Lipid metabolism provides significant amount of metabolic water
  • Dry food also provides some water
  • Kidney is efficient at water recovery
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25
Q

How do Arabian camels thermoregulate when hydrated vs. dehydrated?

A 
Hydrated:
- Panting 
- 36.5-38.5C
Dehydrated:
- Supercooling in night
- Overheating in day
- 34.5-40.5C

Ability to turn off thermoregulation is a water conservation mechanism

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26
Q

How do kangaroo rats regulate water?

A
  • Obtains water from dry food/metabolism
  • Lives in colonies underground (moist air reduces respiratory water loss)
  • Nocturnal (avoid heat of day)
  • Produce very dry feces
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27
Q

What is the typical human urine concentration and urine:blood ratio?

A

Urine conc. = 1400

Urine:Blood ratio = 4.6

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28
Q

How do marine mammals regulate water?

A
  • Obtain water from food and metabolism

- Produce very concentrated urine

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29
Q

How do hibernating bears regulate water?

A
  • Live off of stored fat reserves
  • Reduce body temp., heart rate, metabolic rate
  • Water from lipid metabolism balances respiratory water loss
  • Urea recycled to produce protein
  • Water and urea reabsorbed from kidney
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30
Q

What is the function of the kidneys?

A
  • Regulate extracellular fluid environment by filtering blood, producing urine
  • Involved in homeostasis of blood volume, metabolic waste products, water and electrolyte balance, pH balance
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31
Q

What are the parts of the renal system?

A
  • Renal artery and vein
  • Ureters
  • Urinary bladder
  • Urethra
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32
Q

What is the function of the ureters?

A

Drain urine from the kidneys by peristalsis

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33
Q

What is the function of the urinary bladder?

A

Urine storage

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34
Q

What is the function of the urethra?

A

Drains the bladder

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35
Q

Describe the branching of the renal artery and vein?

A

Renal artery/vein -> Interlobar artery/vein -> Arcuate artery/vein -> Interlobular artery/vein

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36
Q

What are the parts of the kidney (6)?

A
  • Renal cortex
  • Renal medulla
  • Renal pyramids and papillae
  • Renal artery and vein
  • Renal pelvis
  • Ureter
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37
Q

What is the kidney of marine mammals called? Why is it like this?

A
  • Reniculate kidney
  • Increase surface area
  • More efficient at reabsorbing water and getting rid of solute
38
Q

What is the functional unit of the kidney?

A

Nephron

39
Q

How do things travel through the kidney?

A

1 - Blood in at glomerulus
2 - Filtered through nephron
3 - Urine out collecting duct

40
Q

How many nephrons are cortical vs. juxtamedullary?

A

Cortical - 80%

Juxtamedullary - 20%

41
Q

How many nephrons are in the kidney?

A

10^6

42
Q

How are nephrons affected by aging?

A
  • Lost as we age

- Cannot be replaced

43
Q

What are the 4 regions of a nephron?

A

1 - Renal corpuscle (Bowman’s capsule, containing the glomerulus)
2 - Proximal convoluted tubule
3 - Loop of Henle (only region that dips into medulla)
4 - Distal convoluted tubule (BC/glomerulus are close to DCT)

44
Q

What are the nephron associated blood vessels?

A

Afferent and efferent arterioles
- Interlobular artery extends to afferent arteriole
- Efferent arteriole eventually empties into interlobular vein
Peritubular capillaries (vasa recta)
- Extension of efferent arteriole

45
Q

Are the collecting ducts part of the nephron?

A
  • No
46
Q

What 3 steps lead to urine formation in the nephron?

A

1 - Filtration
2 - Reabsorption
3 - Secretion

47
Q

What does the filtration step of urine formation consist of?

A

Movement of fluid from blood to lumen of nephron (‘filtrate’)
- Only takes place in the ‘renal corpuscle’

48
Q

What is the reabsorption step of urine formation?

A

After filtrate leaves Bowman’s capsule, it is modified by reabsorption - solutes in the nephron tubule’s filtrate are moved back to blood

49
Q

Describe secretion in urine formation?

A

Blood moves select solutes back to nephron tubule’s filtrate (form concentration urine)

50
Q

How much fluid enters/exits the nephron each day?

A

180 L fluid enters the nephron, only 1.5 L of urine

51
Q

What are the 3 layers of filtration fluid must pass through to enter the nephron tubule network?

A

1 - Capillary fenestrae (holes in glomerular capillaries)
2 - Basement membrane of glomerular capillaries (rich in collagen)
3 - Inner layer of Bowman’s capsule, consisting of podocytes

52
Q

What is the inner layer of Bowman’s capsule made up of? What is their function?

A
  • Podocytes
  • Podocyte processes and pedicels attached to glomerulus aid in filtration; cell body floats
  • Intricate interdigitation of pedicels
  • Slits between pedicels act as filters
  • Diaphragm slits are negatively charged = barrier to proteins
53
Q

What enters the glomerular filtrate?

A

Only a very small proportion of plasma proteins are filtered, but smaller plasma solutes easily enter the glomerular filtrate

54
Q

What forces blood plasma fluid out of glomerulus into Bowman’s capsule?

A

Blood hydrostatic pressure

55
Q

What is the typical rate of glomerular filtrate production?

A

Men - 180 L/day
Women - 150 L/day
Equivalent to entire blood volume being filtered every 40 minutes

56
Q

What is glomerular filtration rate?

A

Volume of filtrate produced by both kidneys together per minute

57
Q

Does GFR change?

A

BHP can change, but GFR is relatively constant

Relatively stable GFR ensures a constant flow of glomerular filtrate that allows reabsorption and secretion

58
Q

What is the usual GFR?

A

115-125 mL/min

59
Q

How does blood pressure affect GFR?

A

Increased BP:
- Afferent arteriole constricts and efferent arteriole dilates to reduce glomerular BP
Decreased BP:
- Afferent dilates and efferent constricts to increase glomerular BP

60
Q

What are juxtoglomerular cells?

A

Smooth muscle cells of the afferent arteriole

61
Q

What are macula densa cells?

A

Sensory cells in a region of the DCT

62
Q

What are mesangial cells?

A

Communication cells between JG and MD cells via gap junctions

63
Q

What are the sympathetic nerve fibres in the juxtaglomerular apparatus associated with?

A

Afferent arterioles

64
Q

How do JG, MD, MC cells modulate glomerular BP?

A

Vasodilation and vasoconstriction of the afferent arteriole
- Change in BP sensed by MD cells -> communicate via MC cells to JG cells -> JG cells vasodilate or vasoconstrict afferent arteriole

65
Q

What is the function of the sympathetic nerve fibres in the juxtaglomerular apparatus?

A

Redirect blood from kidney to other organ systems

66
Q

What system regulates whole body BP?

A

Renin-Angiotensin-Aldosterone System

67
Q

How does the RAAS regulate whole body BP (5 steps)?

A

1 - BP falls
2 - JG cells secrete RENIN into the blood
3 - Renin acts on ANGIOTENSINOGEN to produce angiotensin 1 (ANGI)
4 - ANGI is converted to ANGII by Angiotensin Converting Enzyme
5 - ANGII is a vasoconstrictor -> increases BP

68
Q

How does RAAS affect blood volume?

A
  • ANGII stimulates aldosterone secretion from the adrenal cortex
  • ANGII and aldosterone work together to increase salt and water reabsorption from the kidneys -> increases blood volume
69
Q

What drugs are commonly prescribed for hypertension/heart disease?

A

ACE inhibitors

70
Q

Which structures are necessary for reabsorption/secretion?

A
  • Peritubular capillaries

- Vasa recta

71
Q

What happens at the peritubular capillaries?

A
  • Blood leaves glomerulus and flows to peritubular capillaries (wind around nephron)
  • They draw water/solutes out of nephron as needed (reabsorption) and send unnecessary water/solutes to nephron (secretion)
72
Q

What proportion of the salt and water in original glomerular filtrate is reabsorbed across PCT and returned to vascular system?

A

65%

73
Q

Where is 20% of salt/water in glomerular filtrate returned to vascular system?

A

Descending limb of LH

74
Q

What are the 2 methods of reabsorption?

A
  • Paracellular

- Transcellular

75
Q

What is paracellular transport?

A

The tight junctions of the PCT cells are quite leaky

76
Q

What is transcellular transport?

A

Solutes can be transported through the cell

77
Q

What drives water reabsorption?

A

Accumulation of salts in interstitial fluid

78
Q

What is the concentration of normal human blood?

A

300 mOsm/L

79
Q

Describe the countercurrent multiplier system?

A

1 - Active transport of NaCl from ASCENDING limb of LH increases the osmolality of the surrounding interstitial fluid (multiplication occurs)
2 - The descending limb of LH is passively permeable to water, which increases the osmolality of the glomerular filtrate
3 - The deepest region in the renal medulla reaches a concentration of 1200-1400 mOsm/L

80
Q

What is the function of the loop of henle?

A

The loop of Henle of juxtamedullary nephrons creates a hyperosmotic environment in renal medulla so urine concentration can occur

81
Q

Which limb of Henle has thicker walls?

A

Thicker walled = ascending limb

82
Q

Describe the ascending limb of the loop of henle?

A
  • Rich in mitochondria
  • Salt is actively extruded to the interstitial fluid, so osmolality increases and osmolality of glomerular filtrate decreases to 300 mOsm/L
  • Permeable to salt
  • Impermeable to water
83
Q

Describe the descending limb of the loop of henle?

A
  • The glomerular filtrate increases in osmolality as it descends (reaches 1200 mOsm/L as it reaches loop turn)
  • Occurs b/c concentrated interstitial fluid draws water out of glomerular filtrate by osmosis
  • Impermeable to salt
  • Permeable to water
84
Q

What happens at the collecting ducts?

A
  • Several nephrons drain into each collecting duct
  • Under the influence of ADH, water is drawn out of filtrate of medullary collecting ducts via aquaporin channels and reabsorbed into the blood
  • ADH must be present to make urine hyperosmotic compared to blood
85
Q

How do aquaporin channels work?

A

1 - ADH binds receptor
2 - Signals via cAMP
3 - Insert AQP apical side
4 - H2O reabsorbed by osmosis into blood

86
Q

What maintains the standing osmotic gradient of the renal medulla?

A

Vasa recta

87
Q

What does the vasa recta do?

A
  • Carry blood into and out of renal medulla

- Work via countercurrent exchange

88
Q

What is the countercurrent exchange system?

A

Diffusion of salt and water into and salt out of peritubular capillaries changes the hypertonicity of the interstitial fluid in the renal medulla

89
Q

What do the ureters do?

A
  • Urine moves from renal pelvis to ureter

- Smooth muscle cells in walls carry urine to bladder via peristalsis

90
Q

What prevents the backflow of urine from bladder?

A

Flap valve

91
Q

Describe urine?

A
  • Hyperosmotic
  • Sterile
  • Pale to dark yellow (urochrome/Hb)
  • Rapidly populated by bacteria (ammonia odour)
  • pH 4.5-8.2
92
Q

What are 5 substances not normally found in urine?

A
  • Protein
  • Glucose
  • Blood cells
  • Hemoglobin
  • Bile

BIOM 3200 (4 decks)

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