Physiology 208 > Renal > Flashcards

Renal Flashcards

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1
Q

Renal History

A
  • urine characteristics have been used as an indicator of health
  • color, clarity, odor, taste
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2
Q

Honey-urine Disease

A
  • diabetes
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3
Q

Most Important Function of the Kidneys

A
  • homeostatic regulation of water and ion content of the blood
  • salt-water balance or fluid-electrolyte balance
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4
Q

Kidney Functions

A
  1. regulation of ECF volume and blood pressure
  2. regulation of osmolarity
  3. maintenance of ion balance
  4. homeostatic regulation of pH
  5. excretion of wastes
  6. production of hormones
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5
Q

Ions that Kidneys Balance

A
  • Na+, K+, Ca2+
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6
Q

Hormones Produced by Kidneys

A
  • erythropoeitin and renin
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7
Q

Excretion of Wastes

A
  • metabolic and xenobiotics
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8
Q

Reserve Capacity

A

1: 1000 born with one kidney

- can lose 3/4 kidney function before affecting homeostasis

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9
Q

CO received

A

20-25%

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10
Q

the kidney is divided into an _____ ______ and an _____ _______

A
  1. outer cortex

2. inner medulla

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11
Q

Urine leaving the _____ flows into the _____ ______ to passing through the ureter into the bladder

A
  1. nephron

2. renal pelvis

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12
Q

Nephrons

A
  • the functional unit of the kidneys
  • 80% cortical nephrons
  • 20% juxtamedullary nephrons
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13
Q

The cortex contains…

A
  • all Bowman’s capsules, proximal and distal tubules
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14
Q

The medulla contains…

A
  • loops of Henle and collecting ducts
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15
Q

Vascular Components in ORDER

A
  1. Renal artery
  2. Afferent arterioles
  3. Glomerulus (capillaries)
  4. Efferent Arterioles
  5. Peritubular Capillaries
  6. Renal Veins
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16
Q

One nephron has ___ arterioles and ____ sets of capillaries that form a _______

A
  1. two
  2. two
  3. portal system
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17
Q

Portal System

A
  • two capillary beds in a series
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18
Q

Tubular Components in ORDER

A
  1. Bowman’s Capsule
  2. Proximal Tubule
  3. Descending loop of Henle
  4. Ascending loop of Henle
  5. Distal tubule
  6. Collecting duct
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19
Q

capillaries at the glomerulus form a _____ mass

A

ball-like

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20
Q

4 Processes in the Kidney

A
  1. Filtration (glomerular)
  2. Reabsorption
  3. Secretion
  4. Excretion
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21
Q

Movement from blood to lumen is…?

A

filtration

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22
Q

Reabsorption

A

from lumen to blood

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23
Q

Secretion

A

from blood to lumen

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24
Q

Excretion

A

from lumen to outside the body

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25
How much is filtered, reabsorbed, excreted per day
- 180L filtered - >99% is reabsorbed - ~1.5 L/day is excreted
26
~70% of reabsorption occurs where?
proximal tubule
27
Loop of Henle
- responsible for creating dilute urine
28
Distal Tubule and Collecting Duct
- regulate salt and water balance under control of hormones
29
T/F: the quantity and composition of substances being absorbed/secreted are equal in diff. segments of nephron
FALSE
30
amount excreted equation
amount filtered - amount reabsorbed + amount secreted
31
Filtration
- filtration of plasma from glomerular into kidney tubule: first step in urine formation
32
What substances make up filtrate?
- plasma and dissolved solutes
33
Where do RBC's and plasma proteins go?
- stay in the blood
34
Filtration Fraction
only 20% of plasma that enters Bowman's Capsule is filtered | - 80% continues to peritubular capillaries
35
Triple Filtration Barrier
1. capillary endothelial cells (fenestrated) 2. basal lamina (EC matrix) 3. podocyte endfeet
36
Podocyte Foot
- surround each capillary - leaves slits through which filtration takes place - can move to alter filtration
37
Mesangial Cells
- between the capillaries - contract to alter blood flow - can alter filtration
38
3 Pressures that govern Filtration
1. hydrostatic pressure 2. colloid osmotic (oncotic) pressure 3. Bowman's capsule hydrostatic pressure
39
Hydrostatic Pressure
- of blood in the glomerular capillaries - favours filtration - ~55 mmHg
40
Colloid Osmotic (Oncotic) Pressure
- of the blood is the pressure gradient due to the presence of plasma proteins - opposes filtration - ~30 mmHg
41
Bowman's Capsule Hydrostatic Pressure
- fluid pressure - opposes filtration - ~15 mmHg
42
Net Filtration Pressure
Ph - pi - Pfluid
43
Glomerular Filtration Rate (GFR)
- the volume of fluid that filters from the glomerular capillaries into the Bowman's capsules/unit time
44
Normal GFR
~125 ml/min or 180L/day
45
How many times a day do the kidneys filter our entire plasma
- 60 times a day | - plasma volume = 3 L
46
If plasma was not absorbed then...
- run out of plasma in 24 min
47
2 Factors Influence GFR
1. Net Filtration Pressure | 2. Filtration Coefficient
48
Net Filtration Pressure
- renal blood flow and blood pressure
49
Filtration Coefficient
- the surface area of the glomerular capillaries available for filtration and permeability of interface between capillaries and Bowman's capsule
50
T/F: GFR is relatively constant?
TRUE | - relatively constant over a wide range of blood pressures
51
How is GFR Regulated?
- primarily by renal arterioles (afferent and efferent)
52
Renal Blood Flow (RBF)
- dependent on overall resistance
53
Overall Resistance
- determined by the resistance in both the afferent and efferent arterioles
54
What happens when afferent dilates and efferent stays the same?
- RBF = increases - hydrostatic pressure = increases - GFR = increases
55
Regulation mainly occurs at the _____ arterioles
AFFERENT
56
T/F: RBF and GFR are always directly proportional
FALSE
57
What happens when afferent constricted and efferent stays the same?
- RBF = decreases - hydrostatic pressure = decreases - GFR = decreases
58
What happens when afferent stays the same and efferent dilates?
- RBF = increases - hydrostatic pressure = decreases - GFR = decreases
59
What happens when afferent stays the same and efferent constricts?
- RBF = decreases - hydrostatic pressure = increases - GFR = increases
60
GFR Autoregulation
- protect the filtration barriers from high blood pressures that would cause damage
61
2 Auto-Regulatory Mechanisms
1. Myogenic response of the afferent arterioles | 2. Tubuloglomerular Feedback
62
Myogenic Autoregulation
- contraction in response to stretch of the vascular smooth muscle - in afferent arteriole
63
Myogenic Response of Afferent Arterioles Process
1. increase intraluminal pressure 2. increase vessel wall tension and VSMC stretch 3. mechano-dependent event 4. depolarization 5. L-type Ca2+ channel activation and Ca2+ entry 6. VSMC contraction
64
Tubuloglomerular Feedback
- local control pathway in which fluid flow through the tubule portion of the nephron influences GFR
65
Macula Densa Cells
- sense distal tubule flow and release paracrine that affect afferent arteriole diameter - become activated by increased NaCl
66
Granular Cells
- secrete renin
67
Renin
- enzyme involved in salt and water balance
68
Tubuloglomerular Feedback Process
1. GFR increases 2. flow through tubule increases 3. flow past macula dense increases 4. paracrine from macula densa to afferent arteriole 5. afferent arteriole constricts 6. resistance in afferent arteriole increases 7. Ph in glomerulus decreases 8. GFR decreases
69
Paracrine Signals during Tubuloglomerular Feedback
- possible ATP being converted to adenosine
70
Integrating Centers Outside of Kidneys
- capable of over riding the local control mechanisms by altering resistance or filtration coefficient
71
Sympathetic Neurons
- release norepinephrine - acts on a1 adrenergic receptors on both afferent and efferent arterioles - results in vasoconstriction
72
Sympathetic Activation
- only alters GFR under conditions of hemorrhage or severe dehydration when water needs to be conserved
73
Hormones that Influence GFR
- angiotensin II - prostaglandins - alter filtration coefficient by acting on podocytes and/or mesangial cells
74
Angiotensin II
- modulate arteriole resistance | - potent vasoconstrictor
75
Prostaglandins
- modulate arteriole resistance | - act as vasodilators
76
Modulation of Podocytes
- changes size of the filtration slits altering permeability for filtration
77
Concentration of Mesangial Cells
- alters capillary surface area available for filtration
78
Less than ____ is actually excreted of 180 L/day
1% (1.5 L)
79
Regulated Reabsorption
- allows kidneys to selectively return ions and water to the plasma to maintain homeostasis
80
Why filter 180L if only 1% is excreted?
- many foreign substances are filtered into the tubules but not reabsorbed (rapid removal) - frequent filtration of ions and water into tubules simplifies regulation and allows it to occur rapidly
81
T/F: Reabsorption may be passive or active
TRUE
82
Filtrate in lumen and ECF initially have _____ solute []'s
similar
83
Active Transport
- used to generate electrochemical, osmotic and concentration gradients for reabsorption
84
Most renal transport is...
TRANSCELLULAR | - uses membrane transporters
85
Basolateral Na+ Transport
- always active transport via Na-K-ATPase - Na+ enters cell, moving down electrochemical gradient - NA+ pumped out
86
Secondary Active Transport
- symport with Na+ - sodium-linked reabsorption: indirect (secondary) active transport - a lot of substances depend on this active transport
87
Passive Reabsorption
ex) urea - nitrogenous waste product - usually urea is equal but as fluid moves urea become diluted in ECF
88
Endocytosis
- very small plasma proteins or peptides
89
Megalin
- receptor mediated endocytosis receptor binding plasma proteins - once in the cell the proteins are digested by lysosomes
90
Saturation
- the maximum rate of transport that occurs when all available carriers are occupied
91
the ____ of substances transported in the nephron use ______ _______
- majority | - membrane proteins
92
Amount of glucose filtered depends on...
- the plasma [glucose]
93
Transport Maximum
- the transport rate at saturation
94
Excess glucose filtered
= more glucose than transporters and some glucose is excreted (diabetes)
95
Glucose
- completely reabsorbed in the proximal
96
Renal Threshold
- the plasma concentration of a solute when it first begins to appear in the urine
97
Glucosuria/Glycosuria
- glucose appearing in your urine - occurs with elevated blood glucose - rare genetic disorder with reduced transporters
98
Peritubular Capillary Pressures Favours...
reabsorption
99
Reabsorption of water and solutes
- water and solutes are reabsorbed from tubule lumen to interstitial space and must reenter circulation
100
Hydrostatic Pressure in Glomerulus
- 55mmHg
101
Hydrostatic Pressure in Glomerulus After Fluid is Removed from Blood
- drops to ~10 mmHg after exiting the glomerulus
102
T/F: Plasma Proteins are filtered
FALSE
103
Oncotic Pressure of Blood to Peritubular
- remains at 30 mmHg as blood travels to peritubular
104
Secretion
- the transfer of molecules from the extracellular fluid into the lumen of the nephron - depends mainly on membrane transport proteins
105
Secretion = Active Process
- requires the movement of substances against their concentration gradients
106
Secretion regulates what?
- homeostatic regulation of K+ and H+ (distal) - regulates organic compounds (medications, food additives in proximal region) - very important
107
Secretion and Excretion
- secretion enhances the excretion of a substance - filtered and not reabsorbed - plus it's secreted then excretion of substance will be very high
108
Tertiary Action Transport
- multi-step process | - secretion of organic solutes
109
OAT Transporter
- tertiary active transporter - uses energy from transporting dicarboxylates down its concentration gradient to move OA- against its concentration gradient
110
aKG-
a-ketoglutarate | - by-product of the citric acid cycle
111
Penicillin
- isolated from bread mold - nearly all penicillin ingested would be excreted within 3-4 hours - given with probenecid
112
Probenecid
- competitor of penicillin | - preferentially secreted by the OAT transporter
113
Fluid at the end of the Nephron
- bears little resemblance to the filtrate
114
Substances Reabsorbed
- glucose, amino acids, useful metabolites
115
Info from Excretion
- tells us what body is eliminating | - can't tell us details of renal function
116
Excretion Equation
= filtration - reabsorption + secretion
117
Renal Handling and GFR
- GFR: indicator of overall kidney function | - renal handling/clearance info on new drugs is necessary
118
Clearance is a _____ way to measure GFR
- noninvasive
119
Accurately Calculate GFR
- look at clearance of a substance that is freely filtered and neither reabsorbed or secreted
120
Inulin
- polysaccharide found in a variety of plants - found in isolated nephrons - completely filtered and not reabsorbed - this is most accurate method, but impractical
121
Filtered Load of X equation
= [X]plasma x GFR
122
GFR Equation
= excretion rate of inulin ----------------------------------- [inulin]plasma
123
Clearance of X Equation
= excretion rate of X (mg/min) ------------------------------------------ [X]plasma (mg/mL plasma)
124
Creatine Clearance
- most commonly used to measure GFR - indicator of renal function - freely filtered by glomerulus, BUT secreted in very small amounts as well - slightly overestimated GFR
125
Creatine
- product of phosphocreatine breakdown | - produced and broken down at relatively stable levels in the body
126
Net Renal Handling
- determined by Clearance - once GFR is known, can look at how their kidneys handle any solute by measuring the solutes plasma concentration and excretion rate
127
How to tell how the nephron handled a substance
- comparing filtered load (filtered freely) with excretion rate OR -* compare GFR to calculated clearance
128
Net Reabsorption
- if less substance appears in the urine than was filtered | - excreted = filtered - reabsorbed
129
Net Secretion
- if more appears in urine than was filtered
130
Net Handling of a Solute
- comparison of clearance values
131
``` GFR = Clearance Filtered = Excreted ```
- filtered, not reabsorbed, not secreted | - ex) inulin
132
GFR > Clearance | Filtered > Excreted
- filtered and net reabsorption | - ex) glucose, urea
133
GFR < Clearance | Filtered < Excreted
- filtered and net secretion | - ex) penicillin
134
Micturition Reflex
- initiated by stretch receptors which are activated by the filling of the bladder
135
Micturition Process
1. stretch receptors fire 2. parasympathetic neurons fire. motor neurons stop firing 3. smooth muscle contracts. internal sphincter is passively pulled open. external sphincter relaxes
136
Urge to urinate appears around _____ ml
200 ml
137
when is the internal sphincter forced to open?
- exceeding 500 ml | - reflexive opening of external sphincter and loss of voluntary opposition
138
How much is left in the bladder after micturition?
~ 10 ml
139
Incontinence
- the inability to control urination voluntarily
140
Incontinence in Infants
- corticospinal connections necessary for voluntary control have yet to be established
141
Incontinence Causes
- infants - damage to internal or external sphincter - spinal cord damage - aging
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