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kidney 2155 > physiology > Flashcards

physiology Flashcards

1
Q

What are the 4 broad functions of the kidney?

A
  1. Homeostatic function
  2. Excretory function
  3. Maintenance of acid-base balance
  4. endocrine functions
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2
Q

What is the primary homeostatic functions of the kidneys?

A
  1. Regulates ECF and blood pressure, ensuring tissue perfusion is within acceptable range.
  2. Regulate inorganic electrolyte concentration in ECF
  3. Regulation of osmolality of ECF (water balance)
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3
Q

What happens when the body releases more water than necessary during prolonged exercise?

body tries to maintain: total intake of water = total output of water

A

CNS sensors detect increased fluid osmolality (so output> input) and send effector signals to:
* Increase thirst
* Release ADH (anti-diuretic hormone) to decrease water output. (through lungs, skin, GI , kidney)

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4
Q

What is the typical total body water percentage for females?

A

50% of body weight.

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5
Q

What is the typical total body water percentage for males?

A

60% of body weight.

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6
Q

How is total body water distributed between fluid compartments?

A

Intracellular fluid (2/3) and extracellular fluid (1/3).

separated by a cell membrane

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7
Q

What are the two components of extracellular fluid? (and how is water distributed?)

A

Interstitial fluid (¾ of ECF) and intravascular plasma (¼ of ECF).

separated by capillary endothelium

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8
Q

What role does the kidney play concerning fluid compartments?

A

Manages the distribution of water in all three fluid compartments through regulation of inorganic electrolyte concentrations and osmolality.

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9
Q

How does kidney regulate all 3 fluid compartments?

A
  1. kidney ONLY receives blood from intravas compartment
  2. kidney interaction w intravas compartment –> interaction with other compartments allow regulation
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10
Q

why does this interaction work? (kidney regulation)

A
  • Starling forces govern the movement of water between plasma (intravascular space) and interstitial fluid.
  • These forces ensure that ECF volume is normally distributed between intravascular and interstitial compartments.
  • Since the intravascular volume is directly proportional to the ECF volume, any changes in kidney function (such as sodium retention or excretion) will influence both plasma volume and interstitial fluid volume.
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11
Q

What are the osmotic factors that control body water distribution? (and how do they do this?)

(thus, regulating inorganic electrolyte conc in ECF)

A
  • ICF: potassium salts (retain water)
  • ECF interstitial fluids + plasma water : sodium salts (can flow easily to either interstitial fluid/plasma water)
  • ECF plasma water: proteins. (remain in plasma + exert oncotiv pressure: draw water into plasma and maintain blood volume)
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12
Q

What is the excretory function of the kidneys?

A

Excretes metabolic waste products and prevents toxic accumulation.

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13
Q

What are examples of nitrogenous waste products excreted by the kidneys?

A
  • Urea
  • Uric acid
  • Creatinine
  • Urobilinogen.
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14
Q

What types of drugs are renally excreted?

A

Low molecular weight and sufficiently water-soluble drugs.

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15
Q

What are the three processes occurring in the nephron?

A
  • Filtration
  • Tubular secretion
  • Reabsorption.
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16
Q

What does the renal corpuscle consist of?

A

Glomerulus and Bowman’s capsule.

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17
Q

What is the filtration barrier in the glomerulus?

A
  • Fenestrated capillary endothelium
  • Basal lamina
  • Bowman’s capsule epithelium.
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18
Q

What size molecules are allowed to filter through the glomerular barrier?

A

Small molecules (<4nm) are free filtered; larger molecules (>8nm) are retained.

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19
Q

How does glomerular filtration pressure affect filtration?

A

Determined by hydrostatic pressure and oncotic pressure.

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20
Q

What happens to GFR when the afferent arteriole constricts?

A

P_GC decreases, GFR decreases, RBF decreases.

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21
Q

What happens to GFR when the efferent arteriole constricts?

A

P_GC increases, GFR increases, but RBF decreases.

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22
Q

What are the two mechanisms that autoregulate renal blood flow?

A
  • Myogenic mechanism
  • Tubuloglomerular feedback.
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23
Q

What are examples of vasodilators in the renal system?

A
  • Prostaglandins
  • Nitric oxide
  • Atrial natriuretic peptide (ANP).
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24
Q

What are examples of vasoconstrictors in the renal system?

A
  • Norepinephrine
  • Catecholamines
  • Angiotensin II.
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25
What is the role of the proximal convoluted tubule?
Major site of isosmotic reabsorption of filtrate.
26
What are the five categories of renal handling of solutes?
* Freely filtered, not reabsorbed, not secreted (e.g. inulin) * Freely filtered, part reabsorbed, not secreted (e.g. sodium) * Freely filtered, all reabsorbed, not secreted (e.g. glucose, AA) * Freely filtered, not reabsorbed, remainder secreted (e.g. PAH) * Freely filtered, part reabsorbed, part secreted (e.g. creatinine, potassium).
27
What determines the level of reabsorption or secretion of a molecule in the nephron?
The asymmetrical polarity of tubular epithelial cells and the distribution of membrane proteins.
28
What is the primary active transport mechanism in the proximal convoluted tubule?
Na+ reabsorption through Na+K+ ATPase.
29
What is the significance of the renal threshold?
The plasma concentration at which transport maximum occurs before saturation.
30
What is the function of the Loop of Henle?
Creates dilute fluid in lumen and concentrated interstitial fluid in renal medulla.
31
What is countercurrent multiplication in the Loop of Henle?
A process that establishes an osmotic gradient through repeated NaCl reabsorption.
32
What occurs during the single effect of countercurrent multiplication?
NaCl is actively reabsorbed from the thick ascending limb into the interstitial fluid.
33
What is the role of the vasa recta in the renal system?
Brings nutrients and oxygen to medullary nephron segments while removing excess water.
34
What is the process that helps maintain osmotic gradient in the kidney?
Countercurrent exchange in the vasa recta ## Footnote Vasa recta is the capillary network that brings blood to the medulla, providing nutrients and oxygen while removing excess water and solutes.
35
What hormone controls sodium and water reabsorption in the distal convoluted tubule?
Aldosterone ## Footnote Aldosterone also plays a role in pH homeostasis.
36
What hormone regulates water reabsorption in the collecting duct?
Vasopressin ## Footnote Vasopressin binds to membrane receptors, activating a second messenger system that increases water permeability.
37
What is the role of urea recycling in the kidney?
It increases the concentrating capacity of the kidney ## Footnote Urea is differentially distributed in the collecting ducts, enhancing osmotic gradient.
38
What is the normal range for plasma pH?
7.35-7.45 ## Footnote This range is crucial for maintaining acid-base balance.
39
What is the primary volatile substance excreted by the lungs?
Carbonic acid in the form of CO2 ## Footnote This is part of the regulation of acid-base balance.
40
What stimulates the release of renin?
Drop in afferent arteriolar pressure ## Footnote Renin is produced in granular cells in the juxtaglomerular apparatus.
41
What are the main hormones produced by the kidneys?
* Renin * 1,25 (OH)2 vitamin D * Erythropoietin
42
How does aldosterone affect sodium reabsorption?
Increases sodium reabsorption in the distal tubules ## Footnote This leads to decreased sodium excretion.
43
What is the osmotic threshold for ADH release?
285 mOsm/kg of H2O ## Footnote ADH plays a key role in maintaining normal plasma osmolality.
44
What is the consequence of hyperkalemia?
Reduces resting potential, leading to arrhythmias ## Footnote Severe hyperkalemia can result in depolarization block and flaccid paralysis.
45
What regulates potassium excretion in the kidneys?
Aldosterone ## Footnote Aldosterone increases potassium secretion in the distal tubules.
46
What is the normal range for plasma calcium levels?
8.5-11 mg/dL ## Footnote About 50% of plasma calcium is ionized.
47
What is the primary function of PTH?
Regulates calcium levels in the blood ## Footnote PTH release is stimulated by low calcium levels.
48
What is the role of FGF-23?
Inhibits phosphate reabsorption ## Footnote FGF-23 is secreted by osteocytes and osteoblasts.
49
What happens when GFR reaches a critical threshold of 30-60 ml/min?
Adaptive changes occur in remaining glomeruli ## Footnote Nephron loss can lead to further nephron loss.
50
How much daily urine volume is produced to ensure waste is dissolved?
Minimum 0.5 L ## Footnote This is necessary to prevent the accumulation of waste products.
51
What is the mechanism of action of aldosterone on cells?
Activates transcription in the nucleus to increase channel and pump synthesis ## Footnote This results in increased sodium reabsorption and potassium secretion.
52
What factors affect GFR and sodium reabsorption?
* Renin-angiotensin-aldosterone system (RAAS) * Intrarenal pressure * Renal sympathetic nerves
53
What is the effect of ANP on sodium excretion?
Increases sodium excretion ## Footnote ANP suppresses renin and aldosterone release.
54
What is obligatory water loss?
0.5 L/day ## Footnote This is the minimum urine volume to prevent waste accumulation.
55
What is the intact renal hypothesis?
Loss of nephron mass results in surviving nephrons trying to compensate through hypertrophy, expansion or hyperfunction in their rates of filtration, reabsorption and secretion. ## Footnote This hypothesis suggests that the remaining nephrons adapt to maintain overall kidney function despite the loss of others.
56
What occurs when GFR reaches a critical threshold of 30-60 ml/min?
Adaptive changes occur in remaining glomeruli and systemic complications arise. ## Footnote This indicates that nephron loss triggers a cascade of further nephron loss and complications.
57
What is the consequence of nephron loss according to the adaptation theories?
Nephron loss begets further nephron loss, leading to progressive renal fibrosis. ## Footnote This progression is often a result of compensatory mechanisms that eventually fail.
58
What complications arise from compensatory mechanisms in renal function?
Proteinuria and angiotensin II advance renal disease. ## Footnote These factors can exacerbate renal damage and accelerate disease progression.
59
What happens with severe or repeated renal injury?
Epithelial cells have impaired proliferative response, resulting in interstitial capillary loss and fibroblast proliferation. ## Footnote This impaired response contributes to further deterioration of kidney function.
60

kidney 2155 (2 decks)

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