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PHYL2062 EOS > Renal 3/4: Micturition and The kidney’s in homeostasis > Flashcards

Renal 3/4: Micturition and The kidney’s in homeostasis Flashcards

1
Q

Urine composition is very different to filtrate. What are the 3 differences?

A
  1. Important molecules are reabsorbed (eg. Glucose, amino acids)
  2. Waste products are concentrated (eg. Urea, drugs)
  3. Ions & water vary depending on blood concentration
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2
Q

How is filtrate different to plasma?

A

filtrate is like plasma but without proteins

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3
Q

What is the function of ureters?

A

Transports urine to bladder

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4
Q

What are the 2 functions of the bladder?

A
  1. Storage of urine
  2. Stretches to accommodate urine, contracts during voiding
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5
Q

What are the 2 functions of the urethra?

A
  1. Transports urine to exterior
  2. Transit of urine is controlled by sphincters
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6
Q

Micturition involves the relaxation of two _____.

A

sphincters

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7
Q

What are the 2 sphincters in charge of micturition?

A
  1. Internal urethral
  2. External urethral
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8
Q

What are the 3 characteristics of the internal urethral sphincter?

A
  1. Smooth muscle
  2. Involuntary
  3. Part of the bladder wall
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9
Q

The internal urethral sphincter is made of _____ muscle

A

Smooth muscle

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10
Q

The internal urethral sphincter is ____ (voluntary/involuntary).

A

involuntary

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11
Q

What are the 2 characteristics of the external urethral sphincter?

A
  1. Skeletal muscle
  2. Voluntary
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12
Q

The external urethral sphincter is made of _____ muscle

A

skeletal

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13
Q

The external urethral sphincter is ____ voluntary/involuntary.

A

voluntary

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14
Q

The micturition reflex is _____ (voluntary/involuntary) and controlled at the _____.

A

involuntary; spinal cord

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15
Q

Filling of the bladder stimulates ____ receptors

A

stretch

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16
Q

Stretch receptors trigger ____ stimulation of the bladder muscle (contraction), which results in the opening of the ____ urethral sphincter.

A

parasympathetic; internal

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17
Q

What is the process of the micturition reflex?

A
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18
Q

Micturition reflex inhibits motor neurons innervating the ____ urethral sphincter

A

external

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19
Q

Micturition is is involuntary- but have voluntary control over it (by controlling ___ sphincter)

A

external

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20
Q

Micturition occurs when there is _____ (opening/closing) of both urethral sphincters?

A

opening

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21
Q

Voluntary signals from cerebral cortex over-rides inhibition of motor neurons. What does that mean for the external sphincter?

A

can override opening of external sphincter (relax) = exhibition = contract = closed (done by sending AP)

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22
Q

The kidneys help to maintain _________ in the body by controlling the composition of the ECF

A

homeostasis

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23
Q

What are 5 inputs into the kidney? How is it produced?

A
  1. Ingestion
  2. Inhalation
  3. Absorption through body surfaces
  4. Injection
  • Produced through metabolism
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24
Q

What are 4 outputs into the kidney? How are they consumed?

A
  1. Kidneys
  2. Lungs
  3. Digestive tract
  4. Body surface (sweat, tears)
  • Consumed through metabolism
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25
Q

The body is in balance when _____ and _____ are equal

A

input; output

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26
Q

What is the acid-base balance?

A

regulation of unbound H+in body fluids

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27
Q

What is an acid?

A

Substances that separate in solution to release H+(and an anion)

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28
Q

What is a base?

A

Remove H+from solution (bicarbonate- H+ ion can bind to this)

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29
Q

The H+concentration in solution is measured by pH.

An increase H+= _____ (increase/decrease) pH (acidic).

A decrease H+= ______ (increase/decrease) pH (basic/alkaline)

A

decrease; increase

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30
Q

Blood pH is maintained within a ____ (wide/narrow) physiological range (7.35-7.45)

A

narrow

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31
Q

Disturbances in pH can result in ______ (below 7.35) or ______ (above 7.45)

A

acidosis; alkalosis

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32
Q

Why is blood pH regulation important? What are 3 factors?

A

Changes in H+concentration affect

  1. Enzymatic activity (they are a certain shape -> to become activated; H+ changes shape)
  2. Excitability of nerve & muscle cells
  3. K+concentration in the body
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33
Q

Where do H+come from? List 3.

A
  1. Cellular respiration (CO2)
    • CO2 + H2O ⇔H2CO3 ⇔ H+ + HCO3-
  2. Breakdown of nutrients
    • Eg. Sulfuricacid & phosphoric acid
  3. Metabolic intermediates
    • Eg. Fatty acids & lactic acid
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34
Q

What are 3 mechanisms for acid-base balance?

A
  1. Buffer systems
  2. Respiratory response
  3. Renal response
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35
Q

What are buffer system? ECF; ICF; urine.

A

Substances that resist (buffer) pH changes by releasing or binding H+ (in all part of body- copes with small changes

Can withstand/resist changes in pH= balance (by binding or releasing H+ ions)

  • ECF: Carbonic acid –bicarbonate system
  • ICF: Protein buffers, phosphate buffer
  • Urine: Phosphate buffer, ammonia
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36
Q

What is respiratory response? List 2 effects.

A
  1. Ventilation can be regulated to increase or decrease CO2release from the body
  2. Quick response (minutes)
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37
Q

What is renal response? List 2 effects.

A
  1. Regulate H+and HCO3-secretion & reabsorption (unlike respiratory response)
  2. Slower response (hours to days)
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38
Q

What are the 4 response to acidosis?

A

Inside the tubule cell:

  1. CO2and H2O → H+& HCO3-
  2. HCO3-is transported into the blood
  3. H+is actively secreted
  4. H+is excreted in the urine
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39
Q

What are the 2 response to alkalosis?

A
  1. Less common than acidosis
  2. Specialised cells in the distal tubule (Type B intercalated cells) secrete HCO3-and reabsorb H+
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40
Q

What are 2 things that acid-base imbalance?

A
  1. Can arise from either respiratory dysfunction or metabolic disturbances
  2. Deviations divided into four general categories
    1. Respiratory acidosis
    2. Respiratory alkalosis
    3. Metabolic acidosis
    4. Metabolic alkalosis
41
Q

What is respiratory acidosis? What is it too much of? What is it caused by? Does renal compensation occur?

A

Too much CO2 ( Increase PCO2)

Cause: Hypoventilation

Renal compensation: Kidneys conserve HCO3-(& excrete H+)

42
Q

What respiratory alkalosis? What is it too little of? What is it caused by? Does renal compensation occur?

A

Reduced CO2(Increase PCO2)

Cause: Hyperventilation

Renal compensation: Kidneys excrete HCO3-(& conserve H+)

43
Q

Water is the most abundant molecule in the body. Females: _____% of body weight Males: ____% of body weight

A

50; 60

44
Q

What are the two fluid compartments in the body?

A
  1. Extracellular fluid (ECF) –plasma & interstitial fluid
  2. Intracellular fluid (ICF)
45
Q

How much fluid is in each compartment?

A

ECF = 33% (1/3) ICF = 66% has more water (2/3)

46
Q

How is fluid balance regulated?

A
  • ECF fluid consists of solutes (eg. Na+& Cl-ions) and water
  • The kidneys control (blood volume) - salt (Na+) reabsorption to maintain ECF volume (&blood pressure)
  • (If put salt in blood –> will retain more water = increase volume) –water reabsorption to maintain ECF osmolarity (dilute= absorb water (can unpair))
47
Q

_______ of water in the nephrons helps to control ECF osmolarity

A

Selective reabsorption

48
Q

What is osmosis?

A

The movement of water from an area of low osmolarityto an area of high osmolarity…..= diluting salt out of blood

(from high [water] –> low [water])

can’t move water against gradient (no active transport)

49
Q

What are 3 things that happens to water molecules if the ECF becomes too concentrated? (>300mOsm) (eg. diarrhea)

A
  1. ECF becomes hypertonic
  2. Water moves into the ECF until equilibrium (to dilute)
  3. Cells shrink
50
Q

What are 3 things that happens to water molecules if the ECF becomes too diluted?

A
  1. ECF becomes hypotonic
  2. Water moves out of the ECF until equilibrium (into cell)
  3. Cells swell
51
Q

To maintain a constant water volume, water intake must _____ water output.

A

equal

52
Q

Water reabsorption is an ______ (active/passive) process.

A

Passive

53
Q

Water reabsorption is osmotically linked to ______ reabsorption. Water reabsorption is hormonally controlled in _____ tubule & ______.

A

Na+ ; distal; collecting duct

54
Q

Most water is reabsorbed thorugh ______.

A

aquaporins

55
Q

What are aquaporins?

A

Type of channels (for water molecules)

56
Q

What happens to water reabsorption in the proximal tubule?

A

water reabsorption paired with Na reabsorption

57
Q

________(moves Na out of cell) provides _______ gradient- to draw water from ______ of cell into _____ into the _______ and then finally into the _____ capillary. interstitial fluid, capillary (through osmosis)

A

Na/K pump; osmotic; lumen; proximal tubular cell; interstitial fluid; peritubular capillary

58
Q

In the proximal tubule _______ are permanently inserted in the _______membrane. As Na+is reabsorbed, ____follows

A

aquaporins; tubular cell; water

59
Q

The water permeability of the distal tubule and collecting duct is controlled by _______-dependent insertion of aquaporins in the ________ membrane

A

vasopressin; luminal

60
Q

What is vasopressin?

A

a hormone that is also called anti-diuretic hormone

61
Q

What is vasopressin/antidiuretic hormone produced by?

A

by hypothalamic neurons

62
Q

Where is vasopressin/anti-diuretic hormone stored and secreted?

A

from the posterior pituitary

63
Q

When is vasopressin/anti-diuretic hormone released?

A

when ECF osmolarityis too high (dominant factor) or blood pressure is very low

reduces amount of urine = help to reabsorb water

64
Q

Is vasopressin’s action directly proportional or inversely proportional to the number of aquaporins.

A

directly proportional

65
Q

What is vasopressin’s action?

A
66
Q

How is high osmolarity, low ECF volume and low arterial blood pressure relived?

A
67
Q

While, the concentration of urine can be varied to meet the body’s needs, water movement is always ________ (ie. Down the concentration gradient).

A

passive

68
Q

How can we make urine that is a DIFFERENT concentration to the normal ECF (300mOsm/L)?

A

Medullary osmotic gradient- inside the kidney- vary how much is absorbed

69
Q

What is the medullary osmotic gradient?

A

Interstitial fluid in medulla becomes more concentrated towards the renal pelvis

70
Q

What is the purpose of the medullary osmotic gradient?

A

Gradient allows selective reabsorption of water in the distal tubule & collecting duct as the filtrate moves towards the renal pelvis

71
Q

The medullary osmotic gradient is established by the _______. How?

A

Loop of Henle process is too complicated- don’t need to know how

72
Q

The medullary osmotic gradient is maintained by the _______.

A

vasa recta

73
Q

What is vasa recta?

A

capillary that goes around specific nephrons (juxta-medullary nephrons)

74
Q

The medullary osmotic gradient is used by the _______.

A

collecting duct

75
Q

What do the features in the medullary look like?

A
76
Q

The loop of Henle plays an important role in _____the osmotic gradient in the renal medulla

A

establishing

77
Q

Specifically, the _______ nephrons span the depth of the medulla and control the osmotic gradient –Humans = 20% of nephron

A

juxtamedullary

78
Q

What are the 2 limbs of the Loop of Henle?

A
  1. Descending limb
  2. Ascending limb
79
Q

What are 2 characteristics of the descending limb of the Loop of Henle?

A
  1. Highly permeable to water (lots of aquaporins)
  2. Does not reabsorb Na+
80
Q

Th descending limb of the Loop of Henle is ______(highly/lowly) permeable to water. This means that it has (many/very little) aquaporins.

A

highly; many

81
Q

Th descending limb of the Loop of Henle ____ (does/doesn’t) absorb Na+.

A

doesn’t

82
Q

What are 2 characteristics of the ascending limb of the Loop of Henle?

A
  1. Actively reabsorbs NaCl
  2. Impermeable to water (no aquaporins)
83
Q

The ascending limb of the Loop of Henle actively reabsorbs _____.

A

NaCl

84
Q

The ascending limb of the Loop of Henle is ______ permeable/impermeable to water. This means that it has (many/very little/no) aquaporins.

A

impermeable; no

85
Q

______ (different/similar) reabsorption capabilities of the descending and ascending limbs allow the gradient to be formed

A

Different

86
Q

The filtrate equilibrates with the medullary interstitial fluid in the_____ (descending/ascending) loop of Henle as water leaves the tubule through aquaporins (permeable to water)

A

descending

87
Q

The filtrate concentration decreases in the ___ (descending/ascending) limb of the loop of Henle as _____ and _____ are pumped out of the filtrate

A

ascending; Na+; Cl-

88
Q

Filtrate leaving the loop of Henle has a ___ (higher/lower) concentration than interstitial fluid.

A

lower (100 mOsm/L)

89
Q

The ________ maintains the medullary osmotic gradient

A

vasa recta

90
Q

What is countercurrent exchange?

A

The hair-pin loop of the vasa recta allows the blood vessels to supply nutrients & oxygen withoutinterrupting the medullary gradient

91
Q

The hair-pin loop of the vasa recta allows the blood vessels to supply nutrients & oxygen _____ (while/without) interrupting the medullary gradient

A

without

92
Q

What would happen if the vasa recta was straight and exited the kidneys through the medulla?

A

NaCl in the medulla would gradually be “washed away” in the blood= no longer have gradient

93
Q

The shape of the vasa recta retains the ______ (hyper/iso/hypo)tonicity of the medulla and the ______ (hyper/iso/hypo)tonicity of the blood

A

hyper; iso

94
Q

The _________ uses the osmotic gradient to control the osmolarity of urine.

A

collecting duct

Vasopressin- how much water is reabsorbed- unpaired to Na reabsorption

95
Q

Filtrate leaving the loop of Henle is (hyper/iso/hypo)tonic at ____mOsm/L.

A

hypo; 100

96
Q

The presence/absence of ______determines whether the filtrate stays hypotonic or becomes hypertonic

A

aquaporins

97
Q

What happens to vasopressin during over hydration? What does that cause?

A

No further reabsorption of water occurs in the distal tubule or collecting duct if vasopressin is absent

98
Q

What happens to vasopressin during dehydration? What does that cause?

A

Release of vasopressin (ADH) causes the insertion of aquaporins and reabsorption of water in the distal tubule and collecting duct.

out of tubule –> interstitial fluid because interstitial fluid is so concentrated

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