Topic 3 Exam 3 Kidney Flashcards
(95 cards)
1
Q
What are some of the purposes of the Kidneys?
A
regulate blood pressure,l ion balance, pH, removes wastes, secrete hormones
2
Q
Why filter so much blood?
A
maintain homeostasis
3
Q
Path of blood through a nephron
(An
Apple
Gets
Even
perused
Every
Vay)
A
artery
afferent arteriole
glomerulus
efferent arteriole
peritubular capillaries\
Vasa Recta
Vein
4
Q
Path of Filtrate through a Nephron
Big
Butts
dont
ask
dumb
catty
cows
A
Blood
Bowman’s Capsule
Proximal Tubule
descending limb of LH
ascending limb of LH
distal tubule
collecting tubule
collecting duct
5
Q
Filtration
A
glomerulus to tubules, non-selective
based on size, like a coffee filter
6
Q
Reabsorption
A
lumen of tubules to blood, selective,
requires channels of transporters from filtrate
ex) glucose
7
Q
Secretion
A
peritubular capillary blood to tubules, selective
requires channels of tranporters,
blood to filtrate
8
Q
Excretion
A
tubules to outside the body (via bladder)
outside the body (pee)
9
Q
T/F Channels btw capillaries & tubules are not required for reabsorption and secretion
A
false
10
Q
What is the filtration formula?
A
F-R+S=E
Filtration-Reabsorption +Secretion= Excretion
11
Q
Mesangial Cells
A
Support and Regulate blood flow in glomerular capillaries
smooth muscle
respond to changes in pressure
12
Q
Podocytes
A
spaces btw their foot processes (slits) form a filter
foot cells
wrap around capillary endothelial cells
slit pores
13
Q
Capillary Endothelial Cells
A
smal gap pores called Fenestration
14
Q
How many layers of the Glomerular Membrane does Filtrate have to pass though
A
3
1) Capillary Endothelial Cell
2) Basement membrane
3) Epithelial Cell (podocyte)
15
Q
How much plasma volume is filtered into Bowman’s capusle?
A
~20%
16
Q
Glomerular Filtration Rate (GFR)
A
amount of plasma filtered per unit time
~125 mL/min
17
Q
What is GFR determined by?
A
Glomerular FIltration Pressure
18
Q
What is GFP?
A
Glomerular Filtration Pressure
driving force for filtration and is the Sum of the Starling Forces:
19
Q
Pgc=
A
Capillary hydrostatic pressure
20
Q
Pi bc=
A
capsule osmotic pressure
(0 under normal circumstances)
21
Q
Pi gc
A
glomerular osmotic pressure
22
Q
Pbc
A
Bowman’s Capsule Hydrostatic Pressure
23
Q
What two factors favor filtration?
blood to filtrate?
A
Pgc=hydstatic pressure in glomerular capillaries
Pibc= osmotic pressure in Bowman’s Capsule
24
Q
What two factors oppose filtration?
A
Pbc=hydrostatic pressure in Bowman’s Capsule
PiGc= Osmotic pressure in Glomerular Cappilaries
25
The amount of a substance X that is excreted in Joe's urine
increases. If the amount of the substance that was filtered did not
change, what caused this increase?
E = F – R + S
If F is constant and E went up, either less of substance X was reabsorbed or more was
secreted (the ratio of secretion relative to re-absorption went up)
26
Substance Y cannot be reabsorbed or secreted. If the amount
of substance Y in the urine increases, what must have happened?
E = F – R + S
R and S are 0, so the only way to increase E is to increase F
27
If the efferent arteriole from the glomerulus is constricted, what
happens to glomerular filtration pressure (GFP)? Why? What
happens to glomerular filtration rate (GFR)?
Constriction of the efferent arteriole will increase resistance and therefore increase GFP.
Increased GFP will cause increased GFR.
28
Steve's blood albumin levels drop suddenly, what happens to
GFR? Why?
Remember that albumin is one of the most common proteins in the blood and is large such that it cannot cross capillary walls (including the glomerulus).
It is a critical
determinant of glomerular capillary osmotic pressure (πGC) which acts to reduce GFP.
Reduced blood albumin would therefore reduce πGC, leading to increased GFP and GFR.
29
Constant infusion of inulin for measurement of GFR is time-consuming and
expensive. In practice, creatinine is often used. It is naturally produced in
your body and is freely filtered. However, it is also secreted in small amounts.
Given this, will an estimate of GFR based on creatinine clearance be an
overestimate or an underestimate? Explain.
In using clearance of a substance to estimate GFR, you are assuming that it is freely
filtered and neither reabsorbed or secreted:
Excretion = Filtration – Reabsorption + Secretion
In the case of creatinine, there is a little bit of secretion (movement of creatinine from the
blood to the filtrate). This will increase the amount of creatinine detected in the urine,
leading to an overestimate of GFR.
30
GFP=
Pgc+PIbc-Pbc-Pigc
31
How can GFR be a constant across a range of blood pressures?
the Zone of Autoregulation where the GFR stays stable from 80-180 MAP mmgh
32
Within the zone of autoregulation, there are 3 mechanisms of
intrinsic control......
1) Myogenic Regulation
2) Tubuloglomerular Feedback
3) Mesangial Cell Contraction
33
Myogenic Regulation
Smooth Muscle of the afferent arteriole contracts when it is stretched
increased arterial pressure stretches the afferent arterioles, causing it to constrict
up resistance, down bloodflow
Down Pgc, GFP, GFR
34
Tubuloglomerular Feedback
macula densa senses fluid flow and releases paracrines that act on the afferent arteriole
up fluid flow, =contraction of afferent arteriole=down GFR
down Pgc, GFP, GFR
35
Mesangial Cell Contraction
contract in response to stretching, decreasing the SA for filtration
constriction of the glomerular capillary
36
When does Extrinsic Control of GFR take over?
acute, SEVERE changes in blood volume,
GFR is reduced, conserving water
1) baroreceptor Reflex on
2) MAP=CO*TPR=down MAP=upCO, upTPR
3) fluid is conserved, conserved
37
Clinical Applications of GFR...
Filtered Load,
Clearance,
Measuring Renal Plasma Flow,
38
FIltered Load
How much of a particular solute is filtered per unit time
freely cross the gomerular membrane
E=F
39
clearance
E=F
x is freely filtered and not secreted or reabsorbed, then CLEARANCE X=GFR
EX) INULIN!!!!!
40
how do you determine GFR from a substance?
INULIN YOU BITCH
41
Measuring Renal Plasma FLow
PAH is FREELY FILTERED and is NOT REABSORBED
any PAH that does not get filtered is completely SECRETED
PAH=RENAL PLASMA FLOW (RPF)
E=F+S
42
dU/dt=
urine production rate/flow
43
Creatinine
freely filtered, only secreted in small amounts
clearance of creatinine gives GFR
44
Reabsorption
takes place in proximal and distal tubules of the nephron
45
What are the main barriers to movement in Reabsorption?
Apical and Basolateral Membranes of the tubular epithelium
46
What are the three types of reabsorption from filtrate back to blood?
1) Active Solute Transport
2) Passive Water Movement
3) Passive Solute movement
47
Active solute transport
transporters can be on the apical or basolateral membrane
48
Passive Water Movement
transport of things increases plasma osmolarity so water follows
salt goes in, water follows
49
Passive Solute Movement
tubular concentration of solute Z is higher so it moves to the plasma (often following water)
without help, using only open channels (hence passive)
50
How much water and salt reabsorption happen in the PROXIMAL TUBULE?
70%
51
____ is key for the movement of solutes into the kidney
Na+
52
Much of the energy used for the kidneys is for the _________ pump
sodium potassium pump
constantly limits na
and the reason why the kidney uses so much ATP
53
when the kidney's capacity to reabsorb is exceeded, what happens?
EXCRETION!
54
GLUCOSE
Freely filtered,
NEVER SECRETED
E=F-R
55
Tm
Transport Maximum
when all transporters for a substance are taken
56
Renal Threshold
the plasma concentration at which the solute shows up in Urine
57
Diabetes Mellitus
'sweet siphon'
due to not enough Type I or Type II secretion to insulin, GLUCOSE IS NOT MOVED OUT OF THE BLOOD
FL of glucose> Tm of gluose
excess gluose is excreted in urine
58
Secretion
from peritubular capillaries and vasa recta (blood) into tubular lumen (filtrate)
59
Fluid Balance
1) most of your body water comes in through food/drink
2) most of you body water is peed out
3) normally, fluid in=fluid out
60
Hypovolemia
decreased plasma volume and results when water loss exceeds water gain
LOOSING MORE WATER THAN GAINING
61
Hypervolemia
increased plasma volume and results when water gain exceeds water loss
TOO MUCH WATER
62
Hyper and Hypo volemia and have what consequences?
directly affects MAP
change osmolarity of the cells in the body
63
How do your kidneys maintain water balance?
by changing the concentration of urine through antidiuresis and diuresis
64
antidiuresis:
if there is TOO LITTLE water in the plasma, SAVE WATER (CONCENTRATED URINE)
65
DIURESIS
TOO MUCH WATER
DILUTE URINE (GET RID OF WATER)
66
How do your kidneys change urine concentratoin?
by changing the permeability of the collecting duct.
any by altering the number of aquaporins (water pores_
67
Osmolarity increases ________ _______ ___ __ ________ creating a
strong gradient for driving water
from the filtrate (lumen of the
kidney) to the extracellular space.
from the cortex to the medulla
68
If the collecting duct membrane is permeable, what does water do?
water flows out of the filtrate concentrating the urine (antidiuresis)
69
lots of aquaporins......
what happens to water?
means that urine concentrated and water flows out
70
few aquaporins.....
what happens to water>?
water flows in, and urine is diluted
71
How do you change the number of aquaporins?
Vasopressin (ADH)
binds to g-protein leading to insertion of aquaporin 2 channels in the apical membrane
72
How do you change the permeability of the collecting
duct
by regulating vasopressin
73
Low circulating ADH = _______ _______ = reduced permeability
= diuresis = _____ ______ = removal of excess water
fewer aquaporins
dilute urine
74
High circulating ADH = more aquaporins = ________ ________
= antidiuresis = concentrated urine = water saved
increased permeability
75
More vasopressin (ADH) =
= more water conservation
76
How is vasopressin (ADH) regulated?
The hypothalamic neurons projecting to the posterior pituitary
secrete more vasopressin (ADH) in response to:
77
The hypothalamic neurons projecting to the posterior pituitary
secrete more vasopressin (ADH) in response to:
up osmolarity in hypothalamus
down MAP and Blood Volume
78
Any reduction in plasma volume (hypovolemia)
triggers.......
vasopressin release and water
conservation
ex) excessive sweating, diarrhea, hemorrhage
79
Diabetes insipidous
'tasteless'
excessive urin production and thirst
4 types
80
Neurogenic:
defect in the pituitary or hypothalamus – little
production of ADH
excessive urine
81
Nehprogenic
defect in the kidney's response to ADH (could be
due to mutation in ADH receptor or mutation in aquaporin 2).
broken ADH suppresor
82
Dipsogenic
damagic to hypothalamic thirst center
take in too much water
83
Gestational
overproduction of vasopressinase by mom
vpinase breaks down VP excessively
84
normovolemia
water in=water out
85
How does your body maintain Na+
homeostasis?
...by regulating reabsorption
86
Is na+ freely filter?
Na+ is freely filtered at the glomerulus and it is not secreted
87
How is Na+ reabsorbed?
Na+ reabsorption differs slightly in the proximal and distal tubules:
But the general pattern is the same
sodium potassium pump, na moves out
na from tubular fluid moves down its concentration gradient into cell
88
How is Na+ reabsorption regulated?
by aldosterone
up sodiuim potassiuim pumps in apical and basolateral membranes
89
Increased aldosterone has
two effects on the late distal
tubules and collecting ducts:
1) up sodium potassium channels in apical membrane
2) stimulates synthesis of sodium potassiuim pumps in basolateral membrane
90
more aldosterone =
more Na+ reabsorption and more K+ secretion
91
How is aldosterone regulated?
1) cells of the Macula Densa release a paracrine signal in
response to low Na+ in the distal
tubule (this indicates low fluid flow
or low blood pressure)
2)This signal triggers granular
cells of the juxtaglomerular
apparatus to release renin
92
increased renin =
increased aldosterone
93
How does renin increase circulating aldosterone?
1. Liver secretes **Angiotensinogen**
2. Juxtaglomerular cells secrete renin which cleaves *Angiotensinogen to
Angiotensin I*
3. Capillary endothelial cells secrete Angiotensin-converting enzyme (ACE),
which cleaves Angiotensin I to Angiotensin II.
4. Angiotensin II stimulates adrenal cortex to secrete aldosterone.
94
K+
reabsorbed and secreted in nephron
regulated by secretin in late distal tubules and collecting duct
Aldosterone has opposite effects on Na+ and K+
95
increased aldosterone =
more Na+ reabsorption
more K+ secretion
