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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
_______ is the volume of filtrate/minute formed by all glomeruli in the kidneys
Glomerular Filtration Rate (GFR)
26
Glomerular Filtration Rate (GFR) is directly proportional to:
1. Net Filtration Pressure (NFP) 2. Surface area of all glomeruli 3. Filtration membrane permeability
27
Net Filtration Pressure (NFP)
NFP = HPgc – (HPcs + OPgc) Main controllable factor Glomerular hydrostatic pressure (HPgc) biggest influence – change diameter of arterioles
28
Changing capillary hydrostatic pressure commonly impacts NFP and therefore ___
GFR
29
Disease processes can affect number of _____ or integrity of filtration membrane
glomeruli (surface area)
30
Glomerular Filtration Rate is Closely Tied to ___
Homeostasis
31
Kidneys need constant ___ to make filtrate and maintain extracellular homeostasis
GFR
32
If GFR increases:
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)
33
If GFR decreases:
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)
34
Two Types of Control Mechanisms Regulate GFR
Intrinsic controls Extrinsic controls
35
Intrinsic controls (also called renal autoregulation)
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
Extrinsic controls
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
Adjustments to _________ are the easiest way to impact NFP and therefore GFR
glomerular capillary hydrostatic pressure
38
Intrinsic Control of GFR (Renal Autoregulation):
Myogenic Mechanism
39
Myogenic Mechanism
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
Intrinsic Control of GFR (Renal Autoregulation):
Tubuloglomerular Feedback Mechanism
41
Tubuloglomerular Feedback Mechanism
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
Macula densa cells release vasoconstrictor chemicals =
constricting the afferent arteriole
43
Glomerular hydrostatic pressure decreases and GFR is decreased =
allows more time for NaCl reabsorption
44
The two autoregulatory controls keep GFR relatively constant for blood pressure between =
80 – 180 mm Hg accounting for normal behavior (sleep, posture change, exercise)
45
Extrinsic Control of GFR : Sympathetic Nervous System
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
Sympathetic drive will damage the ___ to save the brain (if GFR decreased too much, too long)
kidney
47
Extrinsic Control of GFR : Renin-Angiotensin-Aldosterone System (RAAS)
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
Renin works as a blood enzyme converting inactive Angiotensinogen to _____
Angiotensin I
49
Angiotensin I is converted by Angiotensin Converting Enzyme (ACE) to ______
Angiotensin II
50
Effects of Angiotensin II :
Vasoconstriction Stimulation of Aldosterone Release Stimulates Na+/Cl- absorption at PCT Stimulates thirst
51
____is major mechanism to increase blood volume and blood pressure
RAAS
52
Intrinsic Controls:
regulate GFR during moderate changes in blood pressure – minute to minute adjustmentsn
53
Extrinsic Controls:
indirectly regulate GFR by maintaining systemic blood pressure in emergency situations
54
There are no known receptors that monitor ____ in body fluids
Na+ levels
55
____is linked to blood pressure and blood volume control mechanisms
Sodium-water balance
56
Changes in blood pressure or volume trigger _____ controls to regulate Na+ content
neural and hormonal
57
Concentration of Na+ :
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
Content of Na+ :
total body Na+ content determines ECF volume and therefore blood pressure
59
Three Hormones affecting Blood Pressure and Volume:
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
Aldosterone Actions at Kidney
Triggers for release from adrenal cortex: renin-angiotensin-aldosterone mechanism (RAAS) mediated by JGA of nephron elevated K concentration in ECF
61
Aldosterone Results
Result: increased reabsorption of Na and secretion of K. Aldosterone effects take hours
62
Aldosterone allows cells in the collecting duct to:
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
Diffusion of sodium through these channels is driven by _____ on _____
Na+/K+ pump basal surface
64
Antidiuretic Hormone Actions at Kidney
ADH=Vasopressin
65
Diuretic –
increases urine production and therefore water excretion
66
Antidiuretic –
decreases urine production so conserves water
67
3 triggers for ADH release:
high blood osmolarity (dehydration) low blood pressure low blood volume
68
ADH increases aquaporin (water channel) insertion into collecting duct cells → _________
water reabsorption Result: more concentrated urine (and increased blood volume)
69
ADH causes insertion of _____ into cells cells in the collecting duct
aquaporin proteins
70
Producing Dilute Urine
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
When we are overhydrated:
↓ Osmolality of extracellular fluids ↓ ADH release from posterior pituitary
72
For dilute urine: No ______ in collecting duct cells
aquaporins
73
Producing Concentrated Urine:
Water is reabsorbed from collecting duct (into vasa recta capillaries). Small amount of concentrated urine is produced because we want to conserve water.
74
For concentrated urine: Aquaporins are inserted into _____ of collecting duct cells
apical membranes
75
When we are dehydrated:
↑ Osmolality of extracellular fluids ↑ ADH release from posterior pituitary
76
The _______ in Necessary for Concentrating Urine
Renal Osmotic Gradient
77
Without the osmotic gradient, we would never be able to concentrate urine over _____
300 mOsm
78
Role of ADH:
ADH determines whether water can be reabsorbed by inserting aquaporins in the collecting duct cells
79
Role of Urea
waste product, but is a solute that aids in formation of osmotic gradient. Urea “cycles” between collecting duct, interstitium, and ascending loop
80
Role of Diuretics – increase urine output:
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
Intake of Water is Regulated by _____
Hypothalamus
82
Dehydration leads to: ↑ osmolality in ECF which stimulates _____ in hypothalamus
thirst centers
83
Decreased plasma volume
Stimulates renin-angiotensin-aldosterone system stimulates thirst centers in hypothalamus

Anatomy Exam 3 (11 decks)

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