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Anatomy Exam 3 > Lecture 4 : Regulation of the Nephron > Flashcards

Lecture 4 : Regulation of the Nephron Flashcards

1
Q

The end of the tubule is where we regulate _____ to “fine tune” filtrate to the needs of the body

A

absorption and secretion

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2
Q

At the DCT and Collecting Duct:

A

Make urine more dilute or more concentrated than blood

Change ion concentrations further

Adjust pH

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3
Q

Cells of the Distal Convoluted Tubule

A

Perform only small amounts of absorption and secretion

Simple cuboidal cells but lighter staining

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4
Q

Cells of the Distal Convoluted Tubule functions:

A

fewer mitochondria needed for less active transport

Few or no microvilli on apical surface
> Need fewer transport proteins here

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5
Q

__________ play a major role in the
fine tuning of urine

A

Collecting Ducts

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6
Q

Note that collecting ducts pass all the way through the medulla to the _____ – they use the osmotic gradient to adjust final water content in the urine

A

renal papilla

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7
Q

The Collecting Ducts receive filtrate from many nephrons and release urine into the ______

A

minor calyx

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8
Q

The collecting duct receives filtrate from nephrons in the renal cortex and contains two cell types:

A

Principal cells – maintain body’s water and sodium balance

Intercalated cells – maintain the acid-base balance in blood

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9
Q

Near the papilla, collecting ducts fuse into papillary ducts with _______

A

columnar epithelium

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10
Q

Once the fluid reaches the end of the papillary duct it is officially called ___ because the processing is done

A

urine

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11
Q

We get feedback from the fluid in the early DCT

A

key area for “sampling” filtrate

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12
Q

The Distal Convoluted Tubule Passes between the Afferent and Efferent Arterioles at the ____

A

Glomerulus

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13
Q

The ________ is a “sensor” region that monitors filtrate formation and blood pressure

A

juxtaglomerular apparatus

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14
Q

JGA consists of 3 types of cells that help regulate rate of filtrate formation and systemic blood pressure. These cells respond to Na levels in filtrate and blood pressure by making adjustments to GFR.

A

mascula densa

granular cells

Extraglomerular mesangial cells

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15
Q

Macula densa

A

(dense spot): cells with chemoreceptors that monitor NaCl content in the filtrate of DCT

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16
Q

Granular cells (JG or Juxtaglomerular cells):

A

specialized smooth muscle cells that act as mechanoreceptors sensing blood pressure in afferent arteriole

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17
Q

Granular cells release the enzyme ___ if needed

A

renin

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18
Q

Extraglomerular mesangial cells

A

can pass regulatory signals between macula densa and granular cells

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19
Q

Outward (out of capillary) pressures ____ filtrate formation:

A

PROMOTE

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20
Q

Hydrostatic pressure in glomerular capillary (HPgc)

A

Glomerular capillary pressure

Higher than normal capillary pressure to ensure filtration across whole length

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21
Q

Inward (into capillary) pressures _____ filtrate formation:

A

OPPOSE

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22
Q

Hydrostatic pressure in the capsular space (HPcs)

A

Pressure exerted by filtrate in the glomerular capsule

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23
Q

Colloid osmotic pressure in glomerular capillary (OPgc)

A

Pressure exerted by proteins in the blood drawing water toward them

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24
Q

A ____ Net Filtration Pressure (NFP) = Filtrate Formation

A

POSITIVE

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25
Q

_______ is the volume of filtrate/minute formed by all glomeruli in the kidneys

A

Glomerular Filtration Rate (GFR)

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26
Q

Glomerular Filtration Rate (GFR) is directly proportional to:

A
  1. Net Filtration Pressure (NFP)
  2. Surface area of all glomeruli
  3. Filtration membrane permeability
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27
Q

Net Filtration Pressure (NFP)

A

NFP = HPgc – (HPcs + OPgc)

Main controllable factor

Glomerular hydrostatic pressure (HPgc) biggest influence – change diameter of arterioles

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28
Q

Changing capillary hydrostatic pressure commonly impacts NFP and therefore ___

A

GFR

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29
Q

Disease processes can affect number of _____ or integrity of filtration membrane

A

glomeruli (surface area)

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30
Q

Glomerular Filtration Rate is Closely Tied to ___

A

Homeostasis

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31
Q

Kidneys need constant ___ to make filtrate and maintain extracellular homeostasis

A

GFR

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32
Q

If GFR increases:

A

more filtrate is formed and urine output increases

Filtrate moves quickly through tubule and substances that would normally be reabsorbed are partially lost in urine (ions, water)

Ion imbalances can result

Blood volume and blood pressure decrease (because water is excreted)

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33
Q

If GFR decreases:

A

less filtrate is formed and urine output decreases

Filtrate moves slowly through tubule and there is more time for reabsorption

Some wastes normally lost in urine are reabsorbed into blood

Blood volume and blood pressure increase (because more water is conserved)

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34
Q

Two Types of Control Mechanisms Regulate GFR

A

Intrinsic controls
Extrinsic controls

35
Q

Intrinsic controls (also called renal autoregulation)

A

act locally within the kidney to maintain GFR despite changes in systemic blood pressure

– changes are minute to minute in response to normal fluctuating changes in blood pressure – allow kidney “to do its job”

Myogenic mechanism

Tubuloglomerular feedback mechanism

36
Q

Extrinsic controls

A

under extreme conditions in which blood pressure falls outside normal range (i.e. hypovolemic shock)

nervous system and endocrine (hormonal) systems kick in to maintain systemic blood pressure and preserve blood flow to brain & vital organs

Nervous regulation : sympathetic nervous system

Hormonal regulation : Renin-Angiotensin-Aldosterone Mechanism (RAAS)

37
Q

Adjustments to _________ are the easiest way to impact NFP and therefore GFR

A

glomerular capillary hydrostatic pressure

38
Q

Intrinsic Control of GFR (Renal Autoregulation):

A

Myogenic Mechanism

39
Q

Myogenic Mechanism

A

Smooth muscle reflexively contracts when stretched & relaxes when not stretched – inherent property of smooth muscle

Increased systemic blood pressure stretches afferent arteriole causing reflexive smooth muscle contraction – blood flow into glomerulus ↓ preventing GFR ↑

40
Q

Intrinsic Control of GFR (Renal Autoregulation):

A

Tubuloglomerular Feedback Mechanism

41
Q

Tubuloglomerular Feedback Mechanism

A

Directed by the macula densa cells in the juxtaglomerular apparatus

Macula densa cells are sensitive to filtrate NaCl concentration in the ascending limb of loop

When GFR increases, time to reabsorb NaCl goes down, and the concentration of NaCl in the ascending limb of loop goes up

42
Q

Macula densa cells release vasoconstrictor chemicals =

A

constricting the afferent arteriole

43
Q

Glomerular hydrostatic pressure decreases and GFR is decreased =

A

allows more time for NaCl reabsorption

44
Q

The two autoregulatory controls keep GFR relatively constant for blood pressure between =

A

80 – 180 mm Hg accounting for normal behavior (sleep, posture change, exercise)

45
Q

Extrinsic Control of GFR : Sympathetic Nervous System

A

Driven by more extreme changes in SYSTEMIC blood pressure which alter baroreceptor activity

Norepinephrine from sympathetic nerve fibers

Epinephrine from adrenal medulla

Afferent arteriole constriction leads to a decreased GFR

conserves water, increases systemic BP

46
Q

Sympathetic drive will damage the ___ to save the brain (if GFR decreased too much, too long)

A

kidney

47
Q

Extrinsic Control of GFR :
Renin-Angiotensin-Aldosterone System (RAAS)

A

Stimuli that cause granular cells of JGA to release renin:

Macula densa cells sense low NaCl in filtrate, and signal granular cells to release renin

Granular cells detect reduced blood pressure in afferent arteriole and release renin

Sympathetic nerves trigger renin release from granular cells

48
Q

Renin works as a blood enzyme converting inactive Angiotensinogen to _____

A

Angiotensin I

49
Q

Angiotensin I is converted by Angiotensin Converting Enzyme (ACE) to ______

A

Angiotensin II

50
Q

Effects of Angiotensin II :

A

Vasoconstriction
Stimulation of Aldosterone Release
Stimulates Na+/Cl- absorption at PCT
Stimulates thirst

51
Q

____is major mechanism to increase blood volume and blood pressure

A

RAAS

52
Q

Intrinsic Controls:

A

regulate GFR during moderate changes in blood pressure – minute to minute adjustmentsn

53
Q

Extrinsic Controls:

A

indirectly regulate GFR by maintaining systemic blood pressure in emergency situations

54
Q

There are no known receptors that monitor ____ in body fluids

A

Na+ levels

55
Q

____is linked to blood pressure and blood volume control mechanisms

A

Sodium-water balance

56
Q

Changes in blood pressure or volume trigger _____ controls to regulate Na+ content

A

neural and hormonal

57
Q

Concentration of Na+ :

A

determines osmolality of ECF and influences excitability of neurons and muscles ; remains stable because of water shifts out of or into cells (shrinkage/swelling of cells)

58
Q

Content of Na+ :

A

total body Na+ content determines ECF volume and therefore blood pressure

59
Q

Three Hormones affecting Blood Pressure and Volume:

A

Aldosterone – reabsorbs Na so increases blood volume and blood pressure

Antidiuretic Hormone (ADH) – reabsorbs water so decreases ECF osmolality

Atrial Natriuretic Peptide (ANP) – decreases blood pressure and blood volume; suppress release of ADH, aldosterone, renin

60
Q

Aldosterone Actions at Kidney

A

Triggers for release from adrenal cortex:

renin-angiotensin-aldosterone mechanism (RAAS) mediated by JGA of nephron
elevated K concentration in ECF

61
Q

Aldosterone Results

A

Result: increased reabsorption of Na and secretion of K.

Aldosterone effects take hours

62
Q

Aldosterone allows cells in the collecting duct to:

A

reabsorb sodium from tubule and return it to the blood

Synthesis of new sodium channels and insertion into apical surface of collecting duct cells

63
Q

Diffusion of sodium through these channels is driven by _____ on _____

A

Na+/K+ pump

basal surface

64
Q

Antidiuretic Hormone Actions at Kidney

A

ADH=Vasopressin

65
Q

Diuretic –

A

increases urine production and therefore water excretion

66
Q

Antidiuretic –

A

decreases urine production so conserves water

67
Q

3 triggers for ADH release:

A

high blood osmolarity (dehydration)

low blood pressure

low blood volume

68
Q

ADH increases aquaporin (water channel) insertion into collecting duct cells → _________

A

water reabsorption

Result: more concentrated urine (and increased blood volume)

69
Q

ADH causes insertion of _____ into cells cells in the collecting duct

A

aquaporin proteins

70
Q

Producing Dilute Urine

A

Water is not reabsorbed from the collecting duct – it stays in the filtrate.

Large amount of dilute urine is produced and excreted because we want to get rid of excess water.

71
Q

When we are overhydrated:

A

↓ Osmolality of extracellular fluids

↓ ADH release from posterior pituitary

72
Q

For dilute urine:
No ______ in collecting duct cells

A

aquaporins

73
Q

Producing Concentrated Urine:

A

Water is reabsorbed from collecting duct (into vasa recta capillaries).

Small amount of concentrated urine is produced because we want to conserve water.

74
Q

For concentrated urine:
Aquaporins are inserted into _____ of collecting duct cells

A

apical membranes

75
Q

When we are dehydrated:

A

↑ Osmolality of extracellular fluids

↑ ADH release from posterior pituitary

76
Q

The _______ in Necessary for Concentrating Urine

A

Renal Osmotic Gradient

77
Q

Without the osmotic gradient, we would never be able to concentrate urine over _____

A

300 mOsm

78
Q

Role of ADH:

A

ADH determines whether water can be reabsorbed by inserting aquaporins in the collecting duct cells

79
Q

Role of Urea

A

waste product, but is a solute that aids in formation of osmotic gradient. Urea “cycles” between collecting duct, interstitium, and ascending loop

80
Q

Role of Diuretics – increase urine output:

A

Alcohol – decreases ADH release

Caffeine – increases GFR, decreases Na reabsorption

Loop diuretics – inhibit formation of osmotic gradient by inhibiting pumps in ascending limb

Other drugs inhibit Na & water reabsorption

81
Q

Intake of Water is Regulated by _____

A

Hypothalamus

82
Q

Dehydration leads to:
↑ osmolality in ECF which stimulates _____ in hypothalamus

A

thirst centers

83
Q

Decreased plasma volume

A

Stimulates renin-angiotensin-aldosterone system

stimulates thirst centers in hypothalamus

Anatomy Exam 3 (11 decks)

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