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nervous system > Overview of Kidney function > Flashcards

Overview of Kidney function Flashcards

1
Q

what is water and electrolyte homeostasis?

A

when intake and loss are in balance over a significant period. it does not happen by accident.

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2
Q

what are some complications that can arise with water and electrolyte imblanance?

A

-haemorrage
-unusual eating or drinking
-severe dehydration, rapid fluid loss from gut or after burns
-unintended consequences of drug actions

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3
Q

what is the typical water input and output a day?

A

input - 2.5L
output -2.5

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4
Q

how do we output water/fluids?

A

-urine (1500ml)
-sweat (100ml)
-faeces (200ml)
-invisible loss (700ml)

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5
Q

what happens when sweat loss increases?

A

urine output can be reduced in these conditions

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6
Q

at rest how much kidney tissue does cardiac output supply?

A

25% Of CO about 200g so about 625ml/100g/min

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7
Q

why do kidneys receive such a high blood flow?

A

much higher flow than is required to support flow, tissue metabolism and make sure its filtered.

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8
Q

what is blood pressure like in golemerular capillaries?

A

high, around 50-60mmHg

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9
Q

what is the structure of a renal artery like?

A

-short
-relatively large radius
-unusual sequence of blood vessels

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10
Q

what is the blood flow like in renal artery?

A

afferent arterioles -> glomerular capillaries -> efferent arterioles -> tubular capillaries -> venule

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11
Q

what is the functional unit for the kidney?

A

nephron

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12
Q

what are the 2 types of nephrons?

A

superficial (shorter) and juxtamedullary (longer)

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13
Q

where is water reabsorption more effective?

A

jaxta-medullary as they have longer loops

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14
Q

what does each nephron look like?

A

-a tube
-the nephron wall is a continuous layer of epithelium
-cell shapes in the walls are very different
-shape reflects activity; surface area ; ion pumping etc

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15
Q

what are the 4 sections of nephrons?

A

-proximal convoluted tubules
-loop
-distal convoluted tubule
-collecting duct

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16
Q

what is ultrafiltration?

A

driven by blood pressure in glomerular capillaries
-high renal blood flow (25%)
-high filtration rate

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17
Q

what is reabsorption?

A

active pumping from filtrate in tubules
-for substances to be retained eg water, glucose, amino acids electrolytes

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18
Q

what is secretion?

A

active pumping into tubules
-for substances to be eliminated faster than filtration alone
-allows H+ ammonia, uric acid and some drugs

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19
Q

Which hormone controls pumping rates?

A

aldosterone can adjust the rates of Na+ and K+ pumping

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20
Q

where does the filtration of small molecules occur?

A

through slits between podocytes
-limited by the space between the podocyte processes

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20
Q

how much salt is recommended?

A

adults should eat no more than 6g of salt a day

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21
Q

where does ultrafiltration occur?

A

glomerular capsule

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22
Q

what is the cut off size for molecules?

A

67KD

23
Q

how is the limit of molecule filtration controlled?

A

-the space between the podocyte process (primary filtration mechanism)
-charge of the molecule (secondary filtration mechanism)

24
Q

in what cases would the filtration mechanisms go wrong?

A

-high blood pressure
-inflammatory disease
-can cause the podocyte processes to move further apart

25
Q

what is the normal glomerular filtration rate

A

90-140ml/min

26
Q

what is the brush border?

A

a layer of densely packed microvilli projecting from the inside surface of a tubular passage.

27
Q

what is the proximal convoluted tubule?

A

site of reabsorption
-has active reabsorption of glucose, amino acids, Na+ and K+ ions
-co-transporters, aqueous channels, membrane pumps
-substantial water reabsorption

28
Q

what should have occurred by the end of the Principle convoluted tubule?

A

-complete reabsorption of glucose, amino acids
-substantial reabsorption of Na+ and water
-volume of filtrate reduced by 2/3rds

29
Q

where is the loop of henle wall thinner?

A

descent into the medulla

30
Q

when is the loop of henle wall thicker?

A

ascent from medulla

31
Q

how does the loop of henle work?

A

-thicker wall on ascent, active pumping out of tubule
-solute diffuses into descending tubule; counter-current mechanism ‘recycles’ solutes
-ion pumping develops high osmotic pressure at the tip of the loop
-no net reabsorption here

32
Q

what makes the high osmotic pressure?

A

most ions can diffuse back into the descending tubule, recirculation of solute generates a region of high osmotic pressure.

33
Q

what happens in the distal convoluted tubule?

A

more solute reabsorption and secretion
-less intense electrolytes and water reabsorption
-DCT ion pumping can be controlled by hormones like aldosterone to fine tune Na+ and K+ exchange.

34
Q

what happens in the collecting duct?

A

-CDs pass close to tips of loop of henle
-if CDs are permeable to water, then moves out of the duct to concentrate filtrate
-duct permeability is set by ADH/AVP

35
Q

what is the normal plasma osmolarity?

A

300 mOsm

36
Q

how is the control of blood osmolarity regulated in a case of restricted water intake?

A
  1. when water intake is restricted, plasma osmolarity increases
  2. more ADH/AVP is secreted by hypothalamus
  3. ADH increases the water permeability of collecting ducts
  4. more water is reabsorbed
  5. concentrated urine is produced
37
Q

what happens when ADH/AVP is present?

A

aquaporins are inserted into the luminal membrane to allow water movement. this rapid insertion/removal allows quick responses

37
Q

what happens when water intake is restricted?

A

plasma osmolarity increases

37
Q

what happens when there is an excess water intake?

A

osmolarity falls
-hypothalamus secretes less ADH/AVP
-collecting duct walls lose permeability to water
-dilute urine produced

37
Q

what is the half life of ADH/AVP in circulation?

A

15 mins

38
Q

what are the juxtaglomerular apparatus?

A

a mass of cells that detects sodium levels in DCT.

38
Q

what does hypo-filtration initiate?

A

-secretion of renin by the juxtaglomerular apparatus

38
Q

what is the function of renin?

A

-splts angiotensinogen to make angiotensin I which is converted to angiotensin II

38
Q

what is low sodium interoperated as?

A

hypofiltration and so low blood pressure

39
Q

what is angiotensin II?

A

a powerful vasoconstrictor

40
Q

what does the renin/ angiotensin/ aldosterone system do?

A

regulates renal blood flow and glomerular filtration rate (low BP, low renal flow, hypo filtration ect.

41
Q

what effect does the sympathetic nerve have on the renin/ angiotensin/ aldosterone system?

A

enhances this action

42
Q

what does aldosterone do?

A

increases reabsorption of Na+ and Cl- ions from loop of henle, DCT AND CD cells. also increases K+ secretion.
-also has effects on outside of kidney, increases absorption of sodium from the gut and reduces excretion of sodium in sweat and tears.

43
Q

how is aldosterone secretion increased?

A

when electrolyte concentrations fall (secreted by glomerulosa cells of the adrenal cortex)

44
Q

what happens when electrolyte absorption increases?

A

water reabsorption also increases

45
Q

what are the 3 components that make up the filtration barrier?

A

-endothelial cells of glomerular capillaries
-golmerular basement membrane
-epithelial cells of Bowmans capsule (podocytes)

46
Q

what is ultrafiltration?

A

filtration that occurs under high pressure

47
Q

how does charge affect filtration

A

negatively charged ions filter less easily
positively charged ions filter easily

48
Q

what is the function of glycocalyx in the glomerulus?

A

restrict negatively charged molecules from being filtered.

nervous system (8 decks)

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