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Human Physiology > Renal Physiology > Flashcards

Renal Physiology Flashcards

Year 1 (TB2)

1
Q

What are the 2 main regions of the kidneys?

A
  1. Cortex - Outer Regions
  2. Medulla - Inner regions
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2
Q

Functional Unit of the Kidneys?

A

Nephrons

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3
Q

Functions of the Kidney

A
  1. Regulation of extracellular fluid volume and blood pressure
  2. Control of ion concentrations (Na+, Cl-, K+, Ca2+)
  3. Maintenance of plasma pH
  4. Regulation of blood composition (290 mOsM/L)
  5. Removal of waste through urine production
  6. Production of hormones
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4
Q

What are the Key Processes in Nephron

A
  1. Filtration
  2. Reabsorption
  3. Secretion
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5
Q

Where does filtration occur?

A

Bowmans Capsule

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6
Q

What are the 3 layers of the filtration barrier?

A
  1. Fenestrated capillary endothelium
  2. Basal lamina (basement membrane)
  3. Epithelium of Bowman’s capsule (podocytes)
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7
Q

How much of the plasma volume (filtration fraction) enters the tutbules?

A

20%

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8
Q

What does the filtration barrier do?

A

Allows the passage of water and small solutes while preventing larger molecules like proteins from entering the filtrate.

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9
Q

What forces drive and oppose filtration in capillaries?

A

Driving Force: Capillary pressure (+55 mmHg)
Opposing Forces:
1. Capillary colloid osmotic pressure (-15 mmHg)
2. Capsule fluid pressure (-30 mmHg)

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10
Q

What is the net inward force of filtration in capillaries?

A

The net inward force is 10 mmHg, calculated as:
+55 mmHg (capillary pressure) - 15 mmHg (colloid osmotic pressure) - 30 mmHg (capsule fluid pressure).

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11
Q

Where does reabsorption occurs?

A

Primarily in the PCT

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12
Q

What substances are reabsorbed?

A
  1. Salts
  2. Water
    3.Glucose
  3. Amino acids
  4. Urea
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13
Q

What are the different mechanism that these substances can be reabsorbed?

A
  1. Diffusion - Passive movement of substances along concentration gradients.
  2. Symporters and antiporters - Coupled transport of molecules across cell membranes.
  3. Active transport - Energy-dependent movement of substances against concentration gradients.
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14
Q

An example of the mechanisms that occurs in the PCT - reabsorption of Na+

A

Na+ is reabsorbed through ion channels, co-transport with glucose (symport), and exchange with H+ (antiporters). The Na+/K+ ATPase pump actively transports Na+ out of the cell into the interstitial space - active transport.

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15
Q

Define Secretion?

A

The process by which substances are selectively moved from the blood across the tubule epithelium into the filtrate.

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16
Q

Why is the process secretion important?

A
  1. Eliminating large molecules that don’t pass through the glomerular filter
  2. Removing waste products and toxins from the blood
  3. Maintaining acid-base balance
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17
Q

What transporters are involved in the active transport mechanisms of secretion?

A

Secretion involves active transport mechanisms utilizing:
Organic Anion Transporters (OAT): OAT1, OAT2, OAT3
Organic Cation Transporter: OCT2

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18
Q

Factors affecting Urine Composition

A
  1. Salt Intake
  2. Water Intake
  3. Sugar and Protein Intake
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19
Q

How does salt intake affect the urine composition?

A

Increased salt consumption leads to increased salt excretion in urine.

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20
Q

How does water intake affect the urine composition?

A

Higher water intake results in increased water excretion in urine.

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21
Q

How does sugar and protein intake affect the urine composition?

A

These do not significantly affect urine composition due to high reabsorption rates in the nephron.

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22
Q

The process of urination is controlled by what?

A

Micturition Reflex

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23
Q

How does Micturition Reflex work?

A
  1. Trigger - Stretch receptors in the bladder wall are activated as the bladder fills.
  2. Muscle action - The detrusor muscle contracts while the sphincters relax.
  3. Urine expulsion - This coordinated muscle action results in the expulsion of urine.
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24
Q

What does the counterurrent multiplier system allow?

A

Allows for the concentration of urine and the conservation of water.

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25
Q

Where is the countercurrent multiplier system primarily occur?

A

Loop of Henle

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26
Q

Descending Limb permeability to water and salts

A

Permeable to water
Relatively impermeable to salts

27
Q

Ascending Limb permeability to water and salts

A

Impermeable to water
Actively transports salts out of the tubule

28
Q

Process of the countercurrent multiplier system

A
  1. Salt Reabsorption
  2. Water Reabsorption
  3. Gradient Amplification
29
Q

Describe salt reabsorption in the countercurrent multiplier system

A

As the filtrate flows up the ascending limb, salts are actively pumped out into the interstitial fluid. This process creates a high osmotic gradient in the medulla.

30
Q

Describe water reabsorption in the countercurrent multiplier system

A

When the filtrate flows back down the descending limb, water moves out of the tubule due to osmosis, following the concentration gradient created by the salt pumps in the ascending limb.

31
Q

Describe the gradient amplification in the countercurrent multiplier system

A

This process is repeated multiple times as the filtrate flows through the loop, progressively increasing the osmotic gradient from the cortex to the inner medulla.

32
Q

Role of urea in the countercurrent multiplier system?

A

Urea is concentrated in the collecting duct and then reabsorbed into the interstitial fluid of the medulla.
This process further increases the osmotic gradient, allowing for even greater water reabsorption.

33
Q

What are the two primary systems involved in renal responses to volume depletion and blood tonicity changes?

A

The Renin-Angiotensin-Aldosterone System (RAAS) and Anti-Diuretic Hormone (ADH).

34
Q

How is RAAS activated in response to decreased blood volume (hypovolemia) or low blood pressure?

A
  1. Detection
  2. Renin Release
  3. Angiotensin Formation
  4. Aldosterone Secretion
  5. Water and Salt Conservation
  6. Thirst Stimulation
35
Q

Describe the detection stage in the activation of RAAS?

A

Juxtaglomerular cells in the kidney detect changes in blood pressure through stretch receptors on arteriolar cells.

36
Q

Describe the renin release stage in the activation of RAAS?

A

The kidney secretes renin into the bloodstream when a fall in arteriolar blood pressure is detected.

37
Q

Describe the angiotensin formation stage in the activation of RAAS?

A

Renin converts angiotensinogen (from the liver) to angiotensin I, which is then converted to angiotensin II by Angiotensin-Converting Enzyme (ACE).

38
Q

Describe the aldosterone secretion stage in the activation of RAAS?

A

Angiotensin II stimulates the adrenal cortex to secrete aldosterone.

39
Q

Describe the water and salt conservation stage in the activation of RAAS?

A

Aldosterone acts on the distal tubules and collecting ducts to increase reabsorption of salt and water, while promoting excretion of K+, H+, and urea.

40
Q

Describe the thirst stimulation stage in the activation of RAAS?

A

Angiotensin II also stimulates the hypothalamus in the CNS, triggering thirst.

41
Q

When RAAS activated?

A

In response to decreased blood volume (hypovolemia) or low blood pressure

42
Q

When is ADH (vasopressin) released?

A

In response to both decreased blood volume/pressure and increased blood osmolarity.

43
Q

How is ADH released in response to both decreased blood volume/pressure and increased blood osmolarity?

A
  1. Stimulation
  2. Release
  3. Water reabsorption
  4. Vasoconstriction
  5. Thirst Stimulation
44
Q

Describe the stimulation stage in the release of ADH

A

ADH secretion is triggered by hypovolemia, hypotension, or blood hypertonicity

45
Q

Describe the release stage in the release of ADH

A

The hypothalamic posterior pituitary secretes ADH into the bloodstream

46
Q

Describe the water reabsorption stage in the release of ADH

A

ADH acts primarily on the distal convoluted tubule (DCT) to stimulate water reabsorption.

47
Q

Describe the vasoconstriction stage in the release of ADH

A

ADH causes vasoconstriction, increasing vascular peripheral resistance.

48
Q

Describe the thirst stimulation stage in the release of ADH

A

ADH also stimulates the thirst centre in the brain.

49
Q

What are the two two main categories that diuretics are classified based on their mechanism of action?

A
  1. Direct-acting
  2. Indirect-acting diuretics.
50
Q

What are the different ways that direct acting diuretics are classified?

A
  1. Loop of Diuretics
  2. Thiazides and other relating drugs
  3. Aldosterone Antagonist
  4. Na+ Channel Blockers
  5. Carbonic Anhydrase Inhibitors
51
Q

What does thiazides and other related drugs do?

A
  1. Act on the distal convoluted tubule
  2. Inhibit sodium reabsorption
52
Q

What does aldosterone Antagonist do?

A
  1. Block the effects of aldosterone in the collecting duct.
  2. Reduce sodium and water reabsorption
53
Q

What does Na+ Channel Blockers do?

A

Inhibit sodium reabsorption in the collecting duct.

54
Q

What does Carbonic Anhydrase Inhibitors do?

A
  1. Act primarily in the proximal convoluted tubule.
  2. Reduce bicarbonate reabsorption
55
Q

What is the main class of indirect-acting diuretics?

A

Osmotic Diuretics

56
Q

What is the mechanism and effect of osmotic diuretics

A
  1. Increase plasma volume, kidney blood flow, and water retention in the filtrate
  2. High filtration with minimal reabsorption, leading to increased urine output
57
Q

What are the therapeutic goals of diuretics ?

A
  1. Reducing fluid volume - Diuretics increase urine production, effectively decreasing the overall fluid volume in the body.
  2. Reducing blood volume - By increasing urine output, diuretics help lower the total blood volume, which can be beneficial in certain cardiovascular conditions.
  3. Reducing excessive pathological edema - Diuretics help eliminate excess extravascular, extracellular fluid, alleviating edema in various parts of the body.
58
Q

How are the therapeutic goals of diuretics achieved through physiological changes?

A
  1. Reduced capillary hydrostatic pressure
  2. Reduced venous pressure
  3. Reduced cardiac load
  4. Reduced interstitial edema
  5. Reduced high blood pressure
59
Q

How does Reduced capillary hydrostatic pressure achieve the therapeutic goals of diuretics?

A

By decreasing fluid volume, diuretics lower the pressure within capillaries.

60
Q

How does Reduced venous pressure achieve the therapeutic goals of diuretics?

A

The decrease in overall fluid volume leads to a reduction in venous pressure.

61
Q

How does Reduced cardiac load achieve the therapeutic goals of diuretics?

A

By lowering blood volume, diuretics decrease the workload on the heart, making them useful in treating heart failure.

62
Q

How does Reduced interstitial edema achieve the therapeutic goals of diuretics?

A

Diuretics help remove excess fluid from tissues, reducing swelling.

63
Q

How does Reduced blood pressure achieve the therapeutic goals of diuretics?

A

The decrease in blood volume contributes to lowering blood pressure, making diuretics valuable in hypertension treatment.

64
Q

What are the side effects of Loop Diuretics

A
  1. Hypokalaemia
  2. Metabolic alkalosis
  3. Hypotension
  4. Hyponatremia
  5. Dehydration
  6. Ototoxicity
  7. Hyperuricemia
  8. Glucose intolerance

Human Physiology (3 decks)

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