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Physiology unit 4 > Renal function, urine formation, and Micturition > Flashcards

Renal function, urine formation, and Micturition Flashcards

1
Q

Which hormoes does the kidney produce

A

EPO, Renin

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2
Q

Which waste products are excreted from the kidneys

A

Ammonia from oxidation that is converted to urea, proteins and nucleic acids are excreted

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3
Q

How do kidneys maintain long-term acid-base balance

A

Secrete or reabsorb H+ or HCO3

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4
Q

What is the pathway of urine production

A

Cortex–> medulla–> minor calyx–> major calyx–> renal pelvis–> ureter

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5
Q

Which artery suplies the kidneys and where does it arise from

A

Renal artery (branch off abdminal aorta)
Very short with large diameter, which creates low resistance for filtration

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6
Q

What is the key vascular structure in the kidneys

A

Glomerulus, capillary bed that is continuous fenestrated for blood filtration

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7
Q

Is afferent or efferent arteriole smaller in kidneys

A

Efferent is smaller

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8
Q

Renal vein function

A

return blood back to IVC

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9
Q

What causes constriction of kidney blood vessils

A

norepinephrine and angiotensin 2
- Sympathetic

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10
Q

Are sympathetic effects stronger on afferent or efferent arterioles

A

Afferent are stronger- decrease filtration rate so we conserve fluid. Don’t create as much filtrate, in sympathetic so constricting vessils

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11
Q

What causes dialation of blood vessels in kidneys

A

Dopamine, Ach
- Parasympathetic activation

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12
Q

Function of nephrons

A

Filter blood and concentrate neuron
Site of exchange between blood and urine

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13
Q

How many nephrons do we have

A

1.3 million in each kidney (2.5 million total)

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14
Q

Function of podocytes

A

form filtration slits

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15
Q

Function of bowman’s capsule

A

start filtrate production

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16
Q

What type of cells are in the collecting duct and what are thier functions

A

P cells- ->Na+ reabsorbtion
I cells–> H+ and HCO3- secretion and reabsorbtion

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17
Q

What do RMICs secrete

A

prostaglandins

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18
Q

Which nephrons have vasa recta

A

In Juxtamedullary nephrons

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19
Q

Function of renorenal reflex

A

maintains kidney balanced in their output. If one ureter senses pressure, decreases efferent nerve activity in other kidney too.

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20
Q

Which types of nephrons have vasa recta on them

A

Medullary nephrons

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21
Q

Where does Filtrate production begin

A

Bowman’s capsule (glomerulus capsule)

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22
Q

What type of capillary bed is the Glomerulus? What is its function?

A

Continuous fenestrated
Filter blood

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23
Q

Vasa recta are alongside _____ nephrons and Peritubular capillaries are alongside ____ nephrons

A

Longer ( Juxtamedullary)
Both (Juxtamedullary and cortical)

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24
Q

Constriction in the kidneys occurs via which 2 hormones

A

Norepinephrine and Angiotensin 2

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25
Q

Dialation in the kidneys occurs via which neurotransmitters

A

Dopamine and Ach

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26
Q

Norepinephrine and Angiotensin 2 have the strongest effect on which arterioles

A

Afferent arterioles

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27
Q

What is the primary site for reabsorbtion in the kidneys, and what special feature does this site have?

A

Proximal Tubule
Has lots of brush border enzymes with lots of microvilli(increases surface area and absorbtion)

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28
Q

Which part of the loop of henle is thick and which is thin

A

Thick: Ascending– Has lots of mitochondira for the active transport of Na
Thin: Descending (very permiable cells to H2O)

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29
Q

What are P cells and what are their function

A

Princapal cells- For Na reabsorbtion

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30
Q

What are I cells and what are their function

A

Intercalated cells, have microvilli and mitochondria, H+ and HCO3- Ion Transport

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31
Q

What are the 2 types of nephrons and what percent does each category make up of the total number ?

A

Cortical- 85% (reabsorb and secrete things)
Juxtamedullary nephrons- 15% (concentrate urine– very long loops of henle).

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32
Q

Is the glomerulus closer to cortical or juxtamedullary nephrons

A

Glomerulus is closer to cortex- medulla junction in juxtamedullary nephrons

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33
Q

What is the main role of RMICs (Renal Medullary Interstitial cells)

A

Secrete Prostaglandins

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34
Q

The Juxtaglomerular apparatus is a junction of

A

Bowman’s capsule, distal tubule, and afferent and efferent arterioles

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35
Q

Where are the granular cells in the juxtamedullary apparatus and what is their significance

A

Are sensing the blood and blood pressure.
All around the afferent arteriole to sense blood pressure and moniter BP. When they detect low BP, they release renin. They have mechanoreceptors.

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36
Q

Where are macula densa cells in the juxtaglomerular apparatus and what is their function here

A

Are sensing Filtrate.
Embedded in the edge of the distal tubule– Have chemoreceptors that measure solute concentration (mostly Na concentration)

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37
Q

Which type of nephrons is the juxtaglomerular apparatus found in

A

Both Medullary and juxtamedullary nephrons

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38
Q

Which parts of the nephron are in the cortex of the kidney

A

Bowman’s capsule
PCT and DCT
Glomerulus
Peritubular capillaries/start of collecting duct

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39
Q

What parts of the nephron are in the medulla of a kidney

A

Vasa recta
Loop of Henle
Most of Collecting duct

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40
Q

What are the 4 steps of the renorenal reflex

A
  1. Increased pressure in ureter in one kidney causes stretch on the ureter
  2. sends afferent signal to spinal cord
  3. Decreased efferent nerve signals to the other kidney, which causes vasodialation of afferent and efferent arterioles.
  4. Increased excretion of Na and water
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41
Q

General function of renorenal reflex

A

Balance kidney output

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42
Q

If one kidney starts to increase urine production, what occurs with the other?

A

It will also increase urine production (renorenal reflex)

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43
Q

Norepinephrine stimulation on tubule cells and granular cells cause what 3 changes

A
  1. Increased sensitivity by granular cells
  2. Increased Na reabsorption
  3. Renal vasoconstriction, which causes Decreased GFR and renal blood flow

Decreases urine production overall–> part of SNS activity

44
Q

How much urine production is there per day and what percentage of total filtrate is this?

A

1.8 L per day
1% of total filtrate–> 99% is brought back into the body

45
Q

What are the 3 anatomical contributions to filtration

A
  1. Large diameter, short renal arteries
  2. Larger afferent arteriole vs efferent
  3. Very leaky fenestrated capillaries
46
Q

Give the role for each Anatomical contributions to filtration:
1) Large diameter, short renal arteries
2) Larger afferent arteriole vs. efferent
3) Very leaky fenestrated capillaries

A

1) increase hydrostatic pressure, increase flow
2) increases hydrostatic pressure
3) high permeability

47
Q

What is the normal rate of filtration at the glomerulus and at which GFR do kidney filtration problems begin?

A

Normal GFR is 125 ml/min
Kidney problems begin if GFR is <60 ml/min

48
Q

How do 1. Increased systemic BP and 2. Decreased systemic BP impact GFR?

A
  1. Increased GFR when systemic BP increases
  2. Decreased BP with decreased GFR
49
Q

When Systemic BP increases, what adjustment is made that causes GFR to go back to normal?

A

Myogenic response- Stretch causes reaction
Afferent arteriole constricts, which sends less blood into the glomerulus

50
Q

When Systemic BP decreases, what adjustment is made that causes GFR to go back to normal?

A

Afferent arteriole dialates, sending more blood back into glomerulus

51
Q

Regulation of GFR occurs via the permiability of ___. This permiability changes based on the contraction or relaxation of ____ cells. What causes this contraction, and what happens to GFR?

A
  • Glomerular capillaries
  • Mesangial cells
  • Angiotensin 2 causes contraction of Mesangial cells, which decreases GFR (decreased permiability)
52
Q

How do neutral substances between 4 and 8 nm pass through glomerular capillaries

A

freely

53
Q

What charge are on the glomerular capillary walls?

A

Negatively charged proteins

This blocks negatively charged things like albumin from entering into filtrate. Albumin would stay in the blood and then go out through renal vein after supplying nutrients to vasa recta with the rest of the blood and peritubular capillaries.

Only small or neutral or positively charged molecules enter filtrate- others stay in the blood and don’t pass into the filtrate

54
Q

Outline the flow of blood through the kidneys

A

Renal artery–> afferent arteriole–> glomerulus–>efferent arteriole–> renal vein
Or, if not becoming filtrate
Renal artery–> peritubular capillaries or vasa recta–> renal vein

55
Q

What is the role of Mesangial cells

A

Change permeability of afferent arterioles (contraction decreases, dilation increases)

56
Q

What is the role of Granular Cells

A

monitor and measure blood pressure via mechanoreceptors. Releases renin when BP is low

57
Q

What is the role of Macula Densa Cells

A

Monitor filtrate and measure solute concentration in filtrate via chemoreceptors (mostly in terms of Na+ conc.)

58
Q

What is the role of I cells

A

Regulate acid-base balance. Intercalated cells that have more microvilli and more mitochondria -> H+ ion and HCO3- ion transport

59
Q

What is the role of P cells

A

Na Reabsorption

60
Q

Overall purpose of Tubuloglomerular feedback

A

Decrease GFR

61
Q

What is glomerular filtration

A

Pull substances out of the blood and into filtrate

62
Q

What is tubular reabsorption

A

Bring substances back into the body that were in the filtrate

63
Q

Filtrate starts with what kind of osmolarity in relation to the blood.

A

Isoosmotic.
Must use active transport via membrane proteins to reabsorb (this creates a gradient)

64
Q

What osmolarity is the medulla

A

Hyperosmotic

In the descending loop, water is reabsorbed (not secreted!) into the surrounding interstitial space of the kidney’s medulla. Water is picked up by the vasa recta to return to blood

In the Ascending loop, Sodium (Na⁺), along with potassium (K⁺) and chloride (Cl⁻), is reabsorbed into the interstitial space of the medulla.

The deeper in the medulla, the more concentrated the filtrate is.

65
Q

What is tubular secretion vs tubular reabsorbtion

A

In Tubular secretion, substances are added to the filtrate
In Tubular reabsorbtion, Substances are removed from the filtrate and added back into the bloodstream

66
Q

Tubular secretion is usually what substances?

A

Waste products! Also, pH balance (i.e. H+ ions or HCO3- ions)

67
Q

Sodium is reabsorbed into the kidney tubule cells via co-transport with which 6 ions/electrolytes?

A

Glucose, Phosphate, Amino Acids, lactate, Hydrogen, Cl

68
Q

Sodium is moved out of the cell that lines the kidney tubules and back into the blood via what mecahnism, and what percent of sodium reabsorbtion occurs in which parts of the nephron?

A

Na/K atpase
60% occurs in proximal tubule
30% occurs in ascending limb of loop of henle
7% occurs in distal tubule
3% occurs in collecting duct

69
Q

What is the primary driver of water reabsorbtion

A

Na reabsorbtion

70
Q

In the Proximal Tubule, What is reabsorbed? Which channels or mecahnisms allow this? What is the effect on osmotic pressure?

A
  • Sodium(Via active transport) ; Nutrients like glucose (Via SGLT2 transporter) and amino acids (Via cotransport with sodium); water(Via aquaporins)

Osmotic pressure does not change

71
Q

How are sodium and water reabsorbed in the proximal tubule?

A

Via active transport
Water follows Na

72
Q

How are glucose and amino acids reabsorbed in the proximal tubule?

A

Glucose: via SGLT1 cotransporter with sodium
Amino Acids: Via cotransport with sodium

73
Q

Descending limb - Loop of Henle
* Highly permeable to:
* Doesn’t transport:

A

Water
Na

74
Q

Ascending limb - Loop of Henle
* Active transport of: _____________ into interstitial space
* Impermeable to:

A

Na
Water

75
Q

What is the result of filtrate modification in the loop of henle

A

Interstitial fluid around the bottom of the loop of henle is hyperosmotic

76
Q

Counter-Current Multiplier Mechanism
Ascending loop:
* What happens?
* Role of vasa recta?

A
  • Na Reabsorption ( Na pumped into vasa recta)
  • Vasa recta picks up some Na
77
Q

Counter-Current Multiplier Mechanism
Descending loop:
* What happens?
* Role of vasa recta?

A
  • Water reabsorbed by osmotic pressure created by Na reabsorption on the other side
  • Vasa recta picks up water
78
Q

What are the 2 goals of the countercurrent multiplier mechanism

A
  1. Reabsorb water
  2. Set up strong concentration gradient next to collecting duct
79
Q

The descending limb secretes what product to help concentrate the interstitial space, and what hormone increases this action

A

Secretes urea
ADH increases this

80
Q

High protein diet leads to → increased ______________ production and increased ability to _______________ urine = __________ urine production

A
  • Urea
    -Concentrate
    -Decreased
81
Q

Filtrate Modification: Distal Tubule
- What is reabsorbed?
- Relatively impermeable to ______________

A

-Na (as much as the body needs
- Water

82
Q

Filtrate Modification: Distal Tubule
- What is secreted? Why?

A

-K + , exchanged with Na+ (high levels of aldosterone - causes K+ secretion)
- H+ (as needed for pH control)

83
Q

Filtrate Modification: Distal Tubule
What is the overall effect on concentration/volume?

A
  • Minor volume reduction
  • Slight dilution of urine

FINE TUNING OF NA+ LEVELS

84
Q

Reabsorption in the collecting duct is controlled by what

A

ADH–> ADH in collecting duct increases H2O reabsorbtion

85
Q

What increases reabsorption in the collecting duct?

A

ADH increases reabsorbtion of water via aquaporin 2 channels

86
Q

What are the 3 effects of aldosterone (what does it increase including channels and ion exchange)

A
  • Increases the number of ENaC’s (Endothelial Na channels)
  • Increases Na/K exchange
  • Increases H/Na exchange
87
Q

What is the effect of caffine on filtration?

A

Caffeine blocks aldosterone action (diuretic effect)

88
Q

Lasix (furosemide) is a loop diuretic → blocks _______________ reabsorption in the ___________________
* How would this make you lose more water?

A
  • Na
  • Ascending loop of Henle
  • You lose more water because there is less of an osmotic gradient, so you don’t pull as much water back into the blood, which causes a greater volume of urine
89
Q

How does ethanol increase water loss

A

Inhibits ADH release from the posterior pituitary

90
Q

What are the effects of alcohol on electrolyte balance?

A

No impact on electrolyte balance, only causes dehydration because more fluid is lost

91
Q

Equation:
RC = UV/P

What does each letter mean?

A

RC = renal clearance
U = concentration of substance in urine
V = flow rate of urine formation
P = concentration of substance in plasma

92
Q

If: RC = GFR
How is filtration, secretion, and reabsorption affected? Examples?

A
  • Freely filtered, not secreted, not reabsorbed
  • Examples: inulin, creatinine
93
Q

What molecules are both good for calculating kidney function?

A

Inulin
Creatinine
Both typically have a RC=GFR

94
Q

If: RC < GFR
How is filtration and reabsorption affected? Examples?

A
  • Freely filtered and reabsorbed (less filtrate in urine)
  • Examples: Na+ ; Glucose, amino acids
  • We don’t want to lose these– want to retain
95
Q

If: RC < GFR
How is filtration and reabsorption affected? Examples?

A
    • Freely filtered and secreted (more filtrate in urine)
  • Examples: K+ , mostly all drug metabolites
96
Q

Clinical application: pharmacists must know the ____________________ for drugs in order to determine correct dosage. Explain how this affects dosage?

A

Renal Clearance
- High Renal Clerance–> Higher dose needed
- Low Renal Clearance–> Lower Dose needed

97
Q

Kidneys funnel urine into ______ _________ from ____________ _____________. It then goes into the _____________ for excretion

A
  • Renal Pelvis
  • Collecting Ducts
  • Ureter
98
Q

How does the ureter move urine

A

Peristaltic contractions

99
Q

What affects the Peristaltic contractions of the ureters? (SNS vs. PNS)

A
  • Parasympathetic: increases contraction of smooth muscle
  • Sympathetic: decreases contraction of smooth muscle
100
Q

Bladder pressure increases _____________ with low volumes less than 500 ml. When above 500ml, pressure increases ________________

A

Slowly
Quickly

101
Q

1) Which urethral sphincter is under voluntary control?
2) Which is involuntary?
3) Detrusor muscle function

A

1) External urethral sphincter
2) Internal urethral sphincter
3) contracts to release urine

102
Q

Micturition reflex purpose and receptors

A

Purpose: Eliminate urine from the bladder
Receptors: Stretch receptors in bladder wall

103
Q

What are the afferent nerves in the micturition reflex

A

Pelvic nerves

104
Q

What are the afferent nerves in the micturition reflex and where do these send signals to?

A

Pelvic nerves are afferent that send signals to sacral region of spinal cord.

105
Q

After the micturition reflex reaches the sacral region of the spinal cord, what efferent nerve then causes an action?

A

The sacral parasympathetic nerves
NOT the vagus nerve

106
Q

Describe the voluntary portion of the micturition reflex

A

External urethral sphincter is voluntary
Motor neurons are inhibited, which relaxes the sphincter, opening it.

107
Q

External urinary sphincter:
______________ (Inhibit or activate) motor neurons → relax → open

A

Inhibit

Physiology unit 4 (5 decks)

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