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Physiology > Renal > Flashcards

Renal Flashcards

1
Q

kidneys regulate:

A

blood vol + blood pressure
- water concentration + fluid vol
- inorganic ion composition
acid-base balance

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2
Q

kidneys excrete:

A

metabolic products: urea, uric acid, creatinine, bilirubin
remove foreign chemicals (drugs, food additives, pesticides)

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3
Q

kidneys synthesize:

A

glucose

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4
Q

kidneys secrete:

A

hormones + enzymes
- erythropoietin
- 1,25 - dihydroxy vitamin D
- renin

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5
Q

total body water

A

in adult male (70kg):
42L
= 60% of total body weight

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6
Q

fluid compartments

A
  • ICF = 40% (inside cells)
  • ECF = 20% (outside of cells) [= ISF (in between tissues) + plasma (inside blood vessels) + CSF]
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7
Q

fluid vol changes in compartements

A
  • during various health disorders ex. vomiting = lots of output
  • by rapid movement of water (osmosis) = flow across membranes
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8
Q

fluid output

A

by urination, respiration, excretion
from kidneys, lungs, feces, sweat, skin

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9
Q

fluid intake

A

water, metabolism, eating

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10
Q

movement of fluid between plasma + ISF

A

(within ECF)

across capillary membrane
movement in/out of lymphatics

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11
Q

movement of fluid between ICF and ECF

A

(between ICF + ISF)

across cell membrane

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12
Q

ionic composition of body fluid compartments

A

electrolytes are managed by kidneys
extracellular [] > intracellular []: Na+, Cl-, and HCO3-
intracellular [] > extracellular []: K+, proteins

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13
Q

gluconeogenesis

A

kidney synthesis of new glucose
usually happens during prolonged fasting (not day-to-day function)

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14
Q

movement of molecules across fluid compartments

A

by diffusion (short distances)
across membrane barriers
dependent on chemical nature of molecules + chemical properties of cell membrane

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15
Q

polar molecules

A

unable to diffuse across membrane bilayer
amino acids, glucose, water

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16
Q

non polar molecules

A

diffuse rapidly across membrane
CO2, fatty acids, steroids

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17
Q

diffusion

A

movement of molecules as a result of their random thermal motion from high to low concentration
results in diffusional equilibrium

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18
Q

diffusional equilibrium

A

over time, equal distribution of solute molecules placed in a solvent

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19
Q

water - diffusion through cell membrane

A

polar molecule
variable rate of diffusion
doesn’t cross membranes easily
dependent on aquaporins
diffusion guided by water concentration

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20
Q

aquaporins

A

water channels in cells
regulated physiologically = variable rate of diffusion

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21
Q

water concentration in solution

A

measured in osmoles and osmolarity

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22
Q

osmole

A

1 mol of solute particles dissolved in water

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23
Q

osmolarity

A

number of solute particles per unit volume of solution
mol/L

water flows from low to high osmolarity
normal osmolarity inside cell ~300 mOsm/L

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24
Q

low osmolarity

A

high water concentration

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25
Q

high osmolarity

A

solution = low water concentration + high solute

addition of solute to solvent (water) lowers [water]

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26
Q

diffusion across two compartments

A

partition between compartments is permeable to water and to solute
both water + solute move from high to low []
movement of water and solute equalizes concentrations on both sides of partition = diffusional equilibrium

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27
Q

osmosis

A

net diffusion of water across a selectively permeable membrane from high to low concentration

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28
Q

osmotic pressure

A

pressure necessary to prevent solvent movement
acts against osmosis

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29
Q

tonicity

A

determined by [non-penetrating solutes] of an extracellular solution relative to the intracellular environment of a cell

[solute] may influence changes in cell vol

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30
Q

non penetrating solutes

A

electrolytes
ex. Na+, K+

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31
Q

isotonic

A

isoosmotic
same concentration of NPS outside and inside the cell
cell vol does not change

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32
Q

hypertonic

A

hyperosmotic
solution has high osmolarity

higher [NPS] outside than inside the cell
cells shrink (low [water] outside = water moves out of cell)

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33
Q

hypotonic

A

hypoosmotic
solution has low osmolarity

lower [NPS] outside than inside of cell
cells swell (high [water] outside = water moves into cell)

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34
Q

filtration

A

movement of solute/water out of blood plasma into ISF

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35
Q

absorption

A

movement of solute/water into blood plasma from ISF

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36
Q

systemic capillaries

A

act as membrane between plasma + ISF
highly permeable to water + most plasma solutes

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37
Q

factors determining fluid movement along capillaries

A

P(c) = capillary hydrostatic pressure
P(IF) = ISF hydrostatic pressure
πc = osmotic force due to plasma protein concentration
πIF = osmotic force due to ISF protein concentration

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38
Q

arterial end of capillary

A

higher pressure
more filtration

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39
Q

venous end of capillary

A

lower pressure
more absorption

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40
Q

Starling Law

A

net filtration pressure = outward pressures - inward pressures
= (Pc + πIF) - (PIF + πc)

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41
Q

homeostasis

A

total body balance of any substance
balance
- gain = ingestion or product of metabolism
- loss = excretion or get metabolized

goal is to maintain homeostasis

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42
Q

retroperitoneal

A

location of kidneys
behind peritoneal cavity (containing GIT) = towards back wall of abdomen

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43
Q

urinary system organs

A

ureter: collect product from kidneys; carry to bladder
bladder: storage for urine
urethra: carry urine from bladder to outside of body

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44
Q

micturition

A

process of emptying bladder
involves autonomic control

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45
Q

kidney anatomy

A

outer capsule = protection
outer cortex = thinner
inner medulla = thicker, made of nephrons
nephrons

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46
Q

nephron

A

functional unit of kidneys
~ 1 mil in one kidney
basic functions: filtration, reabsorption, secretion

renal corpuscle
renal tubule

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47
Q

renal corpuscle

A

filtering unit
glomerulus (capillary bed) + Bowman’s capsule

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48
Q

renal tubule

A

proximal descending tubule + loop of Henle (descending + ascending limbs) + distal convoluted tubule + collecting duct

lined with epithelial cells → vary in structure + function along length of tubule

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49
Q

Bowman’s capsule

A

Bowman’s space
inner wall = podocytes
outer wall = epithelial cells

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50
Q

podocytes

A

continuous epithelial cell layer
forms inner wall of Bowman’s capsule = closest to glomerulus
have cytoplasmic extensions “feet”

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51
Q

epithelial layer differentiation

A
  • basal lamina is trapped between endothelial cells of capillaries + epithelial layer = basement membrane
  • epithelial cell layer differentiates into parietal + visceral layer
    → parietal layer flattened to become wall of Bowman’s capsule
    → visceral layer becomes podocyte cell layer
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52
Q

blood supply to kidney

A

afferent arteriole carries blood in
efferent arteriole carries blood out

rate of flow: 1200 mL/min
cardiac output: 5600 mL/min

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53
Q

renal fraction

A

% of cardiac output going to kidneys
~ 20%
= high blood flow

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54
Q

glomerular filtration layers

A

fenestrated endothelial layer (inside)
basement membrane
podocytes with filtration slits (outside)

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55
Q

cortical nephron

A

85% of nephrons
performs basic functions

majority of nephron is in cortex
collecting duct + small part of loop of Henle are in medulla

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56
Q

juxtamedullary nephron

A

15%
performs basic functions + regulates concentration of urine (reg of osmolarity in medulla)

corpuscle is closer to medulla
all of loop of Henle + collecting duct lie in medulla
proximal + distal tubule are in cortex

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57
Q

glomerular capillaries

A

glomerulus

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58
Q

peritubular capillaries

A

in cortex + are proximal to PCT

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59
Q

vasa recta

A

capillaries in medulla
only in juxtamedullary nephrons
run parallel to loop of Henle

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60
Q

glomerular filtration

A

entry into lumen
from glomerular capillaries into Bowman’s space

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61
Q

filtration holds back:

A

large proteins or albumin
- too large for pores
- neg charge of pores + BM repel neg charged proteins
- semiporous membrane covers podocyte slits

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62
Q

podocyte semiporous membrane

A

nephrins + podocins
selective filtration of blood
proteins should not be in blood → less selective membrane

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63
Q

plasma inflow

A

carries blood to glomerulus
large molecules stay in blood: blood cells, plasma proteins, large anions

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64
Q

filtrate outflow

A

passed through filter
molecules with low MW; water, electrolytes, glucose, aas, fatty acids, vitamins, urea, uric acid, creatinine

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65
Q

proteinuria

A

condition with proteins in the urine
indicates poor kidney function

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66
Q

filtration fraction

A

20%

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67
Q

glomerular capillary blood pressure

A

P(GC)
pushes fluid out of capillary into B. space
favours filtration

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68
Q

fluid pressure in B. space

A

P(BS)
opposes filtration

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69
Q

osmotic force in capillaries

A

πGC
plasma proteins accumulate = ↑ osmolarity
opposes filtration

~0 due to low [protein] in B. space

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70
Q

glomerular filtration rate

A

vol of fluid filtered from glomerulus into B. space per unit time
~125 mL/min in avg man (70 kg)
= 180L/day
→ plasma filtration occurs ~60x/day

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71
Q

factors influencing GFR

A
  1. net glomerular filtration pressure
  2. permeability of corpuscular membrane
  3. surface area available for filtration
  4. neural + endocrine control
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72
Q

net glomerular filtration pressure

A

= P(GC) - [P(BS) + πGC]
always positive
GF pressure initiates urine formation by forcing protein-free filtrate from plasma

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73
Q

permeability of corpuscular membrane

A

(-) charges repel proteins
small pores prevent passage of large proteins

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74
Q

surface area available for filtration

A

↑ SA = ↑ filtration

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75
Q

mesangial cells

A

not part of filtration layers
contraction reduces surface area of glomerular capillaries = ↓ GFR

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76
Q

neural + endocrine control

A

modulation of arteriolar resistance → changes blood flow + GFR
↑ arteriolar resistance = ↓ renal blood flow + ↑ flow to other organs

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77
Q

resistance: ↓ GFR

A

constriction of afferent / dilation of efferent
= ↓ P(GC) = ↓ GFR

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78
Q

resistance: ↑ GFR

A

dilation of afferent / constriction of efferent
= ↑ P(GC) = ↑ GFR

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79
Q

autoregulation of GFR

A

changes to renal blood vessel resistance to compensate for changes in blood pressure → maintenance of GFR
= protection of glomerular capillaries from hypertension trauma

independent of neuronal + hormonal control

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80
Q

myogenic response

A

quick autoregulation
inherent muscle elasticity in blood vessels

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81
Q

tubuloglomerular feedback

A

effect caused by increased tubular flow
signals paracrine response on juxtaglomerular apparatus
causes constriction of afferent arteriole = ↓ GFR

82
Q

mean arterial blood pressure

A

constant GFR over 80-180mm Hg
maintained by autoregulation

83
Q

juxtaglomerular apparatus

A

macula densa
juxtaglomerular cells
mesangial cells

84
Q

macula densa

A

chemoreceptors on wall of distal tubule
sense increased flow ([Na+] + [Cl-])
secrete vasoactive compounds (adenosine) → paracrine signal = vasoconstriction
signals JG cells

85
Q

juxtaglomerular cells

A

granular cells
mechanoreceptors on wall of afferent arteriole
sense circulating plasma vol
controls renin release based on [Na+]

86
Q

filtered load

A

total amount of non-protein or non-protein-bound substance filtered into Bowman’s space
= GFR x [substance in plasma]

87
Q

glucose filtered load

A

[glucose] = 1g/L
GFR = 180L/day

= 180 g/day

88
Q

substance excreted in urine < filtered load

A

indicates reabsorption has occurred

89
Q

substance excreted in urine > filtered load

A

indicates secretion has occurred

90
Q

filtration only

A

inulin, creatinine
excreted

91
Q

filtration + secretion

A

organic acids (para-amino hippuric acid) and bases
drugs, food additives
= excreted

92
Q

filtration + partial reabsorption

A

water, electrolytes
depends on body’s need

93
Q

filtration + complete reabsorption

A

glucose, amino acids
essential for body → returned to blood after filtration

94
Q

substances that undergo filtration + reabsorption

A

water: 180L filtered/day → 99% reabsorbed
sodium: 630g filtered/day → 99.5% reabsorbed
glucose: 180g filtered/day → 100% reabsorbed
urea: 54g filtered/day → only 44% reabsorbed

95
Q

tubular reabsorption

A

movement out of lumen into blood
mediated by transepithelial mediated transport + paracellular diffusion

96
Q

luminal membrane

A

on apical side
between tubular lumen and epithelial cell

97
Q

basolateral membrane

A

on blood side
between epithelial cell and interstitial space (3 sides)

98
Q

reabsorption of Na+

A

mediated transport
transepithelial = across apical + basolateral membranes
driven by Na+/K+ ATPase active transport on basolateral side
movement across apical side varies between regions

99
Q

Na+ reabsorption in proximal tubule

A

mediated transport: from filtrate to ISF
enters cell through membrane proteins, moving down its electrochemical gradient (diffusion across apical side)
pumped out basolateral side by Na+/K+ ATPase

diffusion + bulk transport: from ISF to blood plasma

100
Q

Na+ reabsorption in cortical collecting duct

A

channel-facilitated diffusion

101
Q

glucose reabsorption

A

all filtered glucose is reabsorbed
dependent on Na+

102
Q

glu reabsorption in proximal tubule

A

luminal side: SGLT protein = secondary active transport
- Na+/glu cotransport
basolateral side: GLUT carrier protein = facilitated diffusion

driven by Na+/K+ ATPase

103
Q

glucose clearance

A

zero at normal plasma concentration

104
Q

glucosuria

A

glucose in urine when above renal threshold

105
Q

renal threshold

A

~300mg/100mL plasma glucose
limit for reabsorption
beginning of glucose excretion (proportional increase)

106
Q

transport maximum

A

max capacity of transport proteins for reabsorption= full saturation
reabsorption rate of glucose = 375 mg/min
reach when plasma glucose > 300

107
Q

diabetes mellitus

A

capacity to reabsorb glucose is normal
filtered load is beyond threshold level
= tubules cannot reabsorb glucose

108
Q

renal glucosuria

A

genetic mutation of SGLT
normal blood glucose level
= no glucose reabsorption → excreted

benign / familial renal glucosuria

109
Q

SGLT

A

Na+/glu cotransporter
mediates active reabsorption of glucose in proximal tubules

110
Q

water reabsorption

A

Na+ reabsorption (driven by active transport) creates electrochemical gradient = anion reabsorption
→ solute diffusion creates osmotic gradient = leads to water reabsorption by osmosis

111
Q

urea

A

easily filtered through glomerulus
permeable solute

112
Q

reabsorption of urea

A

by diffusion; dependent on water reabsorption

↑ [urea] as ↓ fluid vol
= diffusion

113
Q

tubular secretion

A

from bloodstream into lumen
coupled to reabsorption of Na+
involves active transport
mostly H+ and K+
choline, creatinine, penicillin

114
Q

renal clearance

A

quantifies kidney function → removal of substances from plasma
measure of vol of plasma that passes through nephron from which substance is completely removed by the kidney per unit time
ml/min of L/h

clearance of S = U(s)V/P(s)
= [substance in urine] x vol of urine passed / [substance in plasma]

115
Q

inulin

A

polysaccharide
not found in body (IV injection to measure GFR)
readily filtered but not reabsorbed, secreted, or metabolized by tubule

116
Q

clearance of inulin

A

U(in) = 300mg/L
V = 0.1L/h
P(in) = 4mg/L

C(in) = 7.5 L/h = 180L/day
= GFR

→ can be used to measure GFR

117
Q

creatinine

A

product of muscle metabolism
clearance can be used to measure GFR clinically (slight overestimate)
filtered, no reabsorption (slight secretion)

GFR ∝ 1/P(cr)
↑ P(cr) = ↓GFR → indicated ↓ nephron function

118
Q

clearance of subst X > GFR

A

X must undergo secretion

119
Q

clearance of subst X < GFR

A

X must undergo reabsorption

120
Q

ion transport in nephron

A

Na+ is actively reabsorbed
Cl- is transported passively when Na+ is pumped out of cell
K+ is secreted into tubules mainly by cells of distal tubule + collecting ducts

121
Q

proximal convoluted tubule

A

(80%) reabsorbs most of the water and non-waste plasma solutes
~ 67% of water reabsorbed in PCT (aqp-1 = always open)
major site of solute secretion (except K+)

122
Q

loop of Henle

A

creates osmotic gradient (in jm nephrons)
reabsorbs large amounts of ions + less amounts of water
different transport capabilities on each side of tubule = countercurrent

123
Q

descending limb of LofH

A

thin
water reabsorption
aqp-1 on luminal + basolateral side of epithelial cell allows passive water transport

124
Q

ascending limb of LofH

A

thick
salt reabsorption (Na+, Cl-, K+)
impermeable to water (no aquaporins)

124
Q

distal convoluted tubule

A

major homeostatic mechanisms of fine control of water and solute to produce urine
12-15% of reabsorption

125
Q

water balance

A

between sources of water gain (input = 1. ingested liquid 2. water from oxidation of food) and water loss (output = 1. insensible: skin, resp airways 2. sweat 3. GI tract, urinary tract, menstrual flow)

126
Q

collecting duct

A

cortical + medullary
cells lining duct are under physiological control

127
Q

water transport along nephron

A

PCT: 67% reabsorped passively (Aqp-1)
LofH: 15% reabsorped passively in descending limb (Aqp-1)
distal tubule: none
collecting duct: remaining (8-17%) reabsorped passively (Aqp-2, -3, -4) → controlled by vasopressin

128
Q

Aqp-1

A

aquaporin
always open
no hormonal control

129
Q

countercurrent multiplication system

A

structure function relationship in loop of Henle
creates osmotic gradient

fluid streams in opposite directions in desc vs asc limbs
multiplication of osmolarity gradient down LofH

130
Q

generation of hyperosmolar ISF in medulla

A

filtrate entering desc limb = isoosmotic (300 mOsm/L)
active transport of NaCl in asc limb = ↓ osmolarity in tubule

net: ↑ [salt] in ISF (compared to asc limb)
= gradient difference of 200 mOsm

131
Q

adaptation of kangaroo rat

A

lives in desert environment
longer loop of Henle = larger interstitial osmolarity gradient to reabsorb maximum water → produce concentrated urine (conserve water)
higher osmolarity in ISF deep in medulla

132
Q

flow along loop + beyond

A

descending limb = concentrated fluid
ascending limb = dilute fluid
distal convoluted tubule = dilute fluid (100 mOsm/L)

133
Q

ADH effect

A

regulates water reabsorption in CD
uses established osmolarity gradient to promote osmosis from tubule of CD through opened aqp-2 = becomes isoosmotic with IS space

134
Q

high osmolarity gradient

A

established in ISF
helps water permeate out of medullar collecting tubule
reabsorption through aqp

135
Q

blood flow in vasa recta

A

flows in opposite direction of filtrate flow in LofH
removes water leaving LofH = serves as counter-current exchangers → maintain Na+ + Cl- gradient (gradient is not washed away)

136
Q

blood flow in medulla

A

low
less than 5% of total renal blood flow
sluggish
prevents solute loss

136
Q

vasa recta capillaries

A

freely permeable to ions, urea, + water → move in + out of capillaries in response to [] gradients
does not create medullary hyperosmolarity but prevents it from being washed out = maintained

137
Q

countercurrent exchange in vasa recta

A

NaCl moves out of ascending limb into ISF → enters descending limb
water diffuses out of desc into asc
= reinforces gradient created by renal tubules
= ↑ [Na+] + [urea] in medullary interstitial space

138
Q

urea recycling

A

100% filtered through glomerulus
50% reabsorbed in PCT
50% is secreted back into loop of Henle (55% reabsorbed from MCD by ADH → 50% f. diffusion; 5% removed by vasa recta)
30% reabsorbed from CCD

139
Q

minimal uptake of urea

A

by vasa recta (5%)
helps maintain high osmolarity in medulla
= only 15% excreted

140
Q

need for concentrated urine

A

kidneys save water by producing hyperosmotic urine

141
Q

mechanisms to maintain hyperosmotic medullary environment

A
  1. counter current anatomy + opposing fluid flow through LofH in JM nephrons
  2. reabsorption of NaCl in asc
  3. impermeability of asc to water
  4. trapping of urea in medulla
  5. hairpin loop of vasa recta
142
Q

anti diuretic hormone

A

vasopressin (controls b.p.)
peptide hormone that regulates water reabsorption through control of aquaporin-2
prevents water loss
↑ ADH = ↑ water retention (less water excreted)

143
Q

ADH secretion

A

osmoreceptors in hypothalamus sense ↑ plasma osmolarity
cells in supraoptic nucleus (hypot) produce ADH
secreted from posterior pituitary

144
Q

ADH mechanism of action

A

acts on collecting duct cells to alter water permeability of luminal membrane

binding of ADH to receptor on basolateral side triggers AQP-2 gene transcription:
AC → cAMP → PKA → phosphorylation = insertion of aqp-2 in luminal membrane

145
Q

water reabsorption in CD cells

A

diffusion through open aqp-2 channels (by ADH)
diffusion across cells + through aqp-3 + 4 channels into ISF

146
Q

diuresis

A

large volume of urine
absence of ADH = CD cells are impermeable to water

147
Q

diabetes insipidus

A

lack of ADH causes water diuresis
central: failure to release ADH from post. pituitary (either synthesis or release is affected)
nephrogenic: ADH has no effect on CD cells (either mut in receptor or affected cascade)

148
Q

water diuresis

A

excretion of excess water
no excess solute in urine
diabetes insipidus

149
Q

osmotic diuresis

A

excess solute + excess water are excreted in urine
uncontrolled diabetes mellitus (excretion of glucose = water follows)

150
Q

ADH increased by

A

shock, pain, warm or hot weather, dehydration
= pee less

ADH acts in CD to ↑ water reabsorption

151
Q

ADH decreased by

A

cold, humid enviro, alcohol, caffeine
= pee more

↓ effect of ADH = smaller gradient created

152
Q

alcohol

A

suppresses ADH secretion

153
Q

body fluid vol + [Na+] reg

A

plasma osmolarity ~ plasma [Na+]
changes in [Na+] cause changes in blood vol + bp

154
Q

baroreceptors

A

nerve endings sensitive to stretch
located in carotid sinus, aortic arch, major veins + intrarenal = JG cells
sense changes in blood vol + peripheral resistance

155
Q

low [Na+] in plasma - short term

A

↓ plasma [Na+] = ↓ plasma vol = ↓ arterial bp
= ↓ stretch = baroreceptors ↓ nerve impulse frequency
↑ activation of sympathetic ANS
constriction of afferent arteriole
= ↓ GFR = ↓ Na+ filtered = ↓ Na+ excreted
↑ plasma [Na+]

156
Q

aldosterone

A

steroid hormone (synthesis requires gene reg. = longer to act)
secreted from adrenal cortex
synthesis triggered by low Na+ (indirectly)
long term effect

157
Q

aldosterone mechanism of action

A

acts on late distal tubule + CCD
induces synthesis of Na+ transporter
= stimulates Na+ reabsorption + ↓ Na+ excretion (also stimulates K+ secretion)

158
Q

RAAS

A

renin-angiotensin aldosterone system

liver produces angiotensinogen protein = released into blood
low [NaCl] is sensed by kidney = JC cells release renin
renin converts angiotensinogen into angiotensin I
ACE converts ATI → ATII
ATII acts on adrenal cortex to control aldosterone secretion (also causes vasoconstriction; ↑ bp)

159
Q

renin secretion

A

low [Na+] triggers juxtaglomerular cells to stimulate renin release:
- sympathetic input from external baroreceptors
- intrarenal baroreceptors
- macula densa signals

160
Q

low [Na+] in plasma - long term

A

↓ plasma [Na+] = ↓ GFR → activation of RAAS
= ↑ aldosterone
→ ↑ Na+ transporter synthesis in CCD cells = ↑ Na+ reabsorption + ↓ Na+ excretion

161
Q

high [Na+] in plasma

A

↑ plasma [Na+] = ↑ ANP secretion =
- inhibition of aldosterone
- inhibition of Na+ reabsorption
- ↑ GFR + Na+ excretion

162
Q

atrial natriuretic peptide

A

peptide hormone
secretion stimulated by ↑ [Na+], ↑ blood vol → atrial distension
synthesized + secreted by cardia atria
acts on kidney cells

163
Q

ANP mechanism of action

A

acts on kidney arterioles → afferent dilation + efferent constriction = ↑ GFR
acts on tubules → ↓ Na+ reabsorption (also through ↓ aldosterone)

= ↑ Na+ excretion

164
Q

K+ regulation

A

most reabsorption = in PCT + LofH
secretion in CD (aldosterone)
[K+] in urine is regulated by CCD

165
Q

↑ K+ in CCD

A

↑ K+ intake = ↑ plasma [K+]
→ ↑ aldosterone secretion from adrenal cortex + ↑ K+ secretion from CCD
= ↑ K+ excretion

166
Q

hyperkalemia

A

excess K+ in blood

167
Q

K+ homeostasis

A

aldosterone secreting cells in adrenal cortex are sensitive to extracellular [K+]
direct release

168
Q

regulation of [H+] in ECF (plasma)

A

maintain ECF pH between 7.35 and 7.45

small changes in pH cause proteins to change shape → alter activity
coupled to K+ imbalances
irregular cardiac beats

169
Q

acidosis

A

arterial plasma pH < 7.35

170
Q

alkalosis

A

arterial plasma pH > 7.45

171
Q

fatal pH

A

pH < 6.8
pH > 7.8

172
Q

acid

A

releases H+ in solution

173
Q

base

A

accepts H+ in solution

174
Q

carbonic acid + bicarbonate

A

CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+
reversible reactions
catalyzed by carbonic anhydrase

175
Q

volatile acid

A

CO2
gas at room temp
produces carbonic acid when reacted with H2O

176
Q

nonvolatile acids

A

organic + inorganic acids from other sources than CO2
phosphoric acid
sulfuric acid

177
Q

production of sulfuric acid

A

metabolism of sulfur-containing amino acids (cysteine, methionine)

178
Q

production of hydrochloric acid

A

metabolism of lysine, arginine, and histidine

179
Q

production of lactic acid

A

metabolism due to intense exercise

180
Q

gain of H+ ions

A
  1. generation of H+ from CO2
  2. production of nonvolatile acids from the metabolism of proteins and other organic molecules
  3. due to loss of HCO3- in diarrhea or other nongastic GI fluids
  4. due to loss of HCO3- in the urine
181
Q

loss of H+ ions

A
  1. utilization of H+ in the metabolism of various organic anions
  2. in vomiting (high [H+] in gastric contents)
  3. secretion = excreted in urine
  4. hyperventilation (↑ CO2 release)
182
Q

buffer

A

any substance that binds to H+
buffer + H+ ↔ Hbuffer

weak acid + its conjugate base

modify change in pH following addition of acids or bases = prevents quick change in pH

183
Q

extracellular buffer system

A

CO2/HCO3-

184
Q

intracellular buffers

A

phosphate ions + proteins
ex. hemoglobin

185
Q

balancing [H+]

A

both kidneys and lungs are responsible
within narrow range

lungs = short term
kidneys = long term (ultimate balancers)

186
Q

respiratory system

A

homeostatic role = short term regulation of H+

↑ [H+] = stimulates ventilation (↑ resp rate)
↓ [H+] = inhibits ventilation

187
Q

causes of resp imbalances

A

hyper/hypo ventilation, respiratory malfunction
non-respiratory causes: fasting, diabetes mellitus = reflex change in ventilation

188
Q

kidneys: alkalosis

A

↓ plasma [H+] (= ↑ HCO3-)
→ kidneys excrete more bicarbonate = ↓HCO3-
results in restoration of acid-base balance

189
Q

kidneys: acidosis

A

↑ plasma [H+] (= ↓ HCO3-)
→ kidney cells synthesize new bicarbonate + send it to blood = ↑ HCO3-
results in restoration of acid-base balance

190
Q

reabsorption of HCO3-

A

dependent on H+ secretion
active process
most of HCO3- is reabsorbed
occurs in proximal tubule, ascending loop of Henle, + CCD
different transport mechanism of H+ depending on part of tubule

191
Q

response to acidosis: mechanism 1

A

if not enough bicarbonate
excess H+ secreted into lumen → binds to HPO42-
HCO3- is generated by tubular cells from CO2 + H2O and diffuses into plasma
net gain of HCO3- in plasma

192
Q

response to acidosis: mechanism 2

A

cells from proximal tubule
uptake of glutamine from glomerular filtrate or peritubular plasma (filtration + secretion)
NH4+ and HCO3- are formed from glutamine inside cells
NH4+ is actively secreted via Na+/NH4+ countertransport into lumen
HCO3- is added to plasma

193
Q

net result of renal regulation of acidosis

A

more bicarbonate synthesized by tubular cells + reabsorbed
= plasma bicarbonate increased
plasma pH returns to 7.4
urine pH is acidic

194
Q

net result of renal regulation of alkalosis

A

bicarbonate is lost in the urine
plasma bicarbonate decreases
plasma pH returns to 7.4
urine pH is alkaline

195
Q

respiratory acidosis

A

decreased ventilation = ↑ blood PCO2
occurs in emphysema
kidneys compensate by secreting H+ to lower plasma [H+]

196
Q

respiratory alkalosis

A

hyperventilation = ↓ blood PCO2
happens at high altitudes (body adaptation to ↑ resp rate)
kidneys compensate by excreting HCO3-

197
Q

metabolic acidosis

A

diarrhea = loss of bicarbonate ions
severe excercise = generate lactic acid
diabetes mellitus

lungs: ↑ ventilation (get rid of CO2 to ↓ [H+])
kidneys: ↑ H+ secretion

198
Q

metabolic alkalosis

A

prolonged vomiting = ↓ [H+]

lungs: ↓ ventilation (↑ CO2)
kidneys: ↑ HCO3- excretion

Physiology (12 decks)

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