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Physiology 2001 > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

The body is __ to __% water depending on the amount of _____

A

45-70%

Fat

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2
Q

What are the functions of the kidney?

A
  1. Maintain water balance in the body
  2. Regulate the volume of ECF and the concentrations of its ions
  3. Maintain blood pH, volume and osmolarity
  4. Excretion of wastes and foreign products
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3
Q

What are Peritubular capillaries?

A

The network of capillaries that surround the nephron

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4
Q

The ____________ and most of the collecting duct are located in the ________.

A

Loop of Henle

Medulla

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5
Q

What is the glomerulus?

A

A ball-like tuft of capillaries where blood plasma is filtered

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6
Q

The _________ arteriole supplys the glomerulus whilst the ________ arteriole drains the glomerulus and subdivides into the ___________ capillaries

A

Afferent
Efferent
Peritubular

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7
Q

Describe Juxtamedullary nephrons:

A

15-20% of the nephrons
Glomerulus in the inner cortex
LoH drops fully into the medulla
Peritubulr capillaries near the LoH become straight and are called Vasa Recta

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8
Q

Describe Cortical nephrons:

A

80-85% of the nephrons
Glomerulus in the outer cortex
LoH only drops slightly into the medulla

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9
Q

Describe the 3 layers of the filtration membrane in the glomerulus

A

Capillary Wall - has pores (is fenestrated)

Basement membrane - mixture of collagen and glycoproteins that repel plasma proteins

Podocytes - foot-like cells that have filtration slits between them

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10
Q

Describe what forces affect glomerular filtration

A

Capillary BP - forces the blood through the filtration membrane.

Colloidal Osmotic pressure - pulls the water from the blood back into the capillary

Bowman’s Capsule Hydro-static pressure - Bottle necking of the capsule causes damming which causes a backwards pressure

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11
Q

What is the Glomerular Filtration Rate and how is it calculated?

A

GFR is the rate of flow of the filtrate

NFP x Kf
Net Filtration Pressure) x(permeability and surface area of glomerulus

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12
Q

What is NFP and how is it calculated?

A

Net Filtration Pressure
It is the sum of the forces affecting glomerular filtration

Capillary BP + Colloidal Osmotic Pressure + Bowman’s Capsule Hydrostatic Pressure

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13
Q

What is Kf?

A

The Filtration coefficient normally 12.5ml/min

it is the permeabilty and surface area of the glomerulus

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14
Q

What are the advantages of a high filtration rate?

A

Rapid removal of wastes and foreign chemicals

Precise and rapid control of fluid volume and composition

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15
Q

Explain the Myogenic mechanism of autoregulation

A

When blood pressure increases the Afferent arteriole is stretched, it responds by constricting

When blood pressure decreases the Afferent arteriole relaxes

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16
Q

Explain the Juxtaglomerular Feedback mechanism of autoregulation

A
  1. Blood pressure increases causing an increase in salt delivery to the macula densa cells
  2. Macula densa cells release ATP and adenosine
  3. ATP and adenosine induce constriction of the afferent arteriole
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17
Q

Autoregulation can be overidden by ____________

A

Sympathetic Stimulation

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18
Q

How does Haemorrhage have an effect on GFR?

A
  1. Decreased plasma volume =>
  2. Decreased arterial BP =>
  3. Barorecptor reflex => Increased Sympathetic output =>
  4. Vasoconstriction of the afferent arteriole =>
  5. Decreased GFR
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19
Q

How does a Large fluid ingestion have an effect on GFR?

A
  1. Increased plasma volume and decrease osmolarity =>
  2. Increased BP =>
  3. Decreased Barorecptor reflex => decreased sympathetic output =>
  4. Vasodilation of afferent arteriole =>
  5. Increased GFR

NB: This overrides autoregulation

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20
Q

Tubular reabsorption is _______________ for required substances. ____% of sugars and ____% of salts are reabsorbed.

A

Highly selective
100% of sugars
99.5% of salts

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21
Q

The nephron tubule is _____ cell(s) thick. Most substances that are reabsorbed go through the _______ to get to the ECF

A

1 cell thick

Go through the cells

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22
Q

When solutes are reabsorbed the ________ of the ECF increases. This causes ______ to move down it’s gradient into the ECF.

A

Osmolarity increases

Water via osmosis

23
Q

___% of obligatory Na reabsorption occurs in the PCT, ___% occurs in the LoH and __% is in the DCT under _______ control

A

67% in PCT
25% in LoH
8% in DCT under hormonal control

24
Q

Explain how Na is reabsorbed:

A
  • Na in the tubule passively diffuses into the low [Na] cell
  • Cell has Na/K pumps which actively transport the Na into the high [Na] ECF
  • Na diffuses from the high [Na] ECF into the low [Na] peritubular cappilaries
25
Q

Explain how Glucose and Amino Acids are reabsorbed:

A
  • Na gradient formed by the Na/K pumps in the tubular cells
  • Na-Glucose and Na-Amino Acid cotransporters allow the passive diffusion of Na into the cell
  • Glucose and Amino Acids are dragged along with the Na
26
Q

When all the _______ and ______ are occupied, no more transport can occur and rate of reabsorption becomes ______. This is known as the ________________

A

Pumps and channels
Constant
Transport Maximum

27
Q

Explain how Chloride is reabsorbed:

A
  • Electrochemical gradient is formed by the Na/K pump and Na transport
  • Anions like Cl- will passively diffuse towards the more positive ECF
  • The tight junctions between tubular cells are impermeable to most things however, Cl- can move through them
28
Q

___% of obligatory water reabsorption occurs in the PCT, ___% occurs in the LoH and ___% occurs in the DCT under hormonal control

A

65%
15%
20%

29
Q

Explain how water is reabsorbed:

A
  • Increased osmolarity of the ECF due to action of Na/K and other solute reabsorption
  • Water will passively move via osmosis
  • Water is another substance that can cross the otherwise impermeable tight junctions
  • Osmolarity of the peritubular capillary is high due to unfiltered proteins .’. water will diffuse into them
30
Q

The descending limb of the LoH is only permeable to ________, the ascending limb is only permeable to ________. This causes a vertical ______________

A

Water
Salts
Osmotic Gradient

31
Q

Na, 2__ and __ are co-transported by a carrier on the _____________

A

Cl and K

Luminal membrane

32
Q

The recycling of ____ contributes to about 40% of the osmolarity of the interstitial fluid. It allows urine to be ________ more easliy

A

Urea

Concentrated

33
Q

Because the _____________ is quite permeable to urea, urea can diffuse into the ________ and contribute to the osmotic gradient.

A

Collecting duct

Interstitial fluid

34
Q

What is the baroreceptor reflex?

A
  • A reflex that responds to blood pressure
  • If blood pressure is high, increased reflex activity will decrease the HR and and cause vasodilation
  • If blood pressure is low, decreased reflex activity will cause HR to increase and cause vasoconstriction
35
Q

Osmoreceptors detect changes in __________ and are found in the ______

A

Osmolarity

Brain

36
Q

Explain how ADH has an affect on the reabsorption of water

A
  • Cells that line form the collecting duct have vesicles that store aquaporins (water channels)
  • ADH binds to receptors on the cells cause vesicles to merge with the membrane
  • Water can be reabsorbed through these channels
37
Q

Explain how ADH counteracts dehydration

A
  1. Increased ECF osmolarity detected by osmoreceptors
  2. ADH is secreted
  3. ADH acts on the nephron causing increased water reabsorption
  4. Osmolarity decreases and blood volume increases
38
Q

What factors increase ADH secretion?

A
  • Increased osmolarity
  • Decreased BP
  • Nicotine
  • Emotional stress, pain, nausea
39
Q

What factors decrease ADH secretion?

A
  • Swallowing

- Alcohol

40
Q

When salt intake increase, levels of ___ and ___ increase which causes water retention to _________. This causes blood pressure to _______.

A

Na+ and Cl-
Increase
Increase

41
Q

When salt intake decreases, osmolarity of the ECF _________ which causes water retention to ________. This causes blood pressure to _______.

A

Decreases
Decrease
Decrease

42
Q

Decreased blood pressure and/or Low plasma NaCl causes what?

A

Decreased Renal Blood Pressure
Increased Sympathetic Output
Decreased Renal Sodium

43
Q

What 3 factors increase secretion of Renin by ________ cells in the ______________?

A

Granular cells in the juxtaglomerular apparatus:

Decreased Renal Blood Pressure
Increased Sympathetic Output
Decreased Renal Sodium

44
Q

Renin converts ____________ to angiotensin 1 which gets converted to angiotensin 2 by _________________ from the lungs. This then stimulates the secretion of _________

A

Angiotensinogen
Angiotensin-Converting enzyme
Aldosterone

45
Q

Angiotensin 2 causes ________ of the _______ arteriole which _______ glomerular filtration rate which _______ water loss and ________ blood pressure

A 
Constriction
Efferent arteriole 
Decreases GFR
Decreases Water loss
Increases BP
46
Q

Angiotensin ______ _________ in the brain which causes ____ secretion to _______

A

Stimulates
Thirst centers
ADH
Increase

47
Q

An increase in atrial blood pressure by __ to __ %causes ______________ to be released by the _________.

A

8-10%
Atrial Natriuretic Peptide/Factor (ANP/ANF)
Atrial cells

48
Q

What does ANP/ANF do?

A

Rapidly brings blood pressure down by:

  • Inhibiting the sympathetics thereby increasing GFR
  • Decreases salt retention by opposing the renin-angiotensin system and directly inhibits Na uptake
  • Decreases water retention by affecting ADH levels
49
Q

K+ levels directly ________ levels of _________ which ________ the number of Na/K pumps on the tubular epithelial cells

A

Increase
Aldosterone
Increases

50
Q

Organic substances like histamine and noradrenline, _____ and ________ are secreted into the ___ via _________

A

Drugs
Pesticides
DCT
Specific Carriers

51
Q

pH must be kept between ___ and ___

A

7.35 and 7.45

52
Q

The lungs regulate ____ levels and the kidney regulates ____ levels

A

CO2

HCO3 -

53
Q

Explain how HCO3- is reabsorbed

A
  1. Because there is no specific carrier for HCO3 - t is converted to H2O and CO2 by carbonic anhydrase in the tubular lumen
  2. As [H2O] and [CO2] levels increase they diffuse into the epithelia
  3. In the epithelia carbonic anhydrase converts it back to HCO3 which can now diffuse into the ECF and peritubular capillary
54
Q

If H+ levels get too high they can be _______________ by H+ pumps. These pumps require ___ to function. To prevent the tubular pH from dropping ___ and _______ are co-secreted

A

Actively secreted
ATP
NH3 and NaPO4 2-

Physiology 2001 (7 decks)

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