Na Homeostasis 2013
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Transcript of Na Homeostasis 2013
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Sodium
(Volume) Homeostasis
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Objectives
Know composition and volume of bodyfluid compartments
Understand systemic regulation of Extra-
Cellular Fluid Volume (ECF) Know neuro-humeral and physical
factors that regulate sodium excretion
Know the cellular mechanisms andpathways for sodium reabsorption in
each nephron segment
Differentiate Na and H2O homeostasis
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x x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o ox x x x x x x x x x x x x x x x o o o o o o o oo o o o o o o o o o o o o o o o x x x x x x x x
Total Body Weight
Water compartment
ECF
ICF
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Volume Depletion
ICF
ECF
Na in
Na out
= H2O
Osmolality
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Water Excess
Osmolality
H2O in
H2O out
H2O
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Water Depletion H2O in
H2O out
Osmolality
H2O
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Afferent (sensory) Limb of ECV
Atrial/ventricular stretch (volume)
Baroreceptors (aortic arch, carotid body)
Afferent renal arteriole
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Primary Regulators ofPrimary Regulators of
volume(Na)volume(Na) Renin-Angiotensin-Aldosterone
Natriuretic Peptides-ANP, BNP,Urodilantin
Renal Sympathetic Nerves
Physical Factors
? Human Ouabain-Like Steroid
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Secondary Regulators ofSecondary Regulators of
Volume (Na)Volume (Na) Nitric Oxide
Endothelin ADH
Prostaglandins
Kinins
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Normal FF (GFR/RPF)
Afferent Efferent
High FF (Volume depletion)
Afferent Efferent
Net Fluid Transport (Na)
Pc
Pc
Peritubular
Capillary
Proximal
Tubule
Peri-
tubular
Capillary
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Normal FF (GFR/RPF)
Afferent Efferent
Low FF (Volume Expansion)
Afferent Efferent
Net Fluid Transport (Na)
Pc
Proximal
Tubule
PeritubularCapillary
Peri-tubular
Capillary
Pc
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HCO3
-+
H+
C.A. Na+
H2O + CO2
Glucose
AA
PO4
3 HCO3-
Na+
K+
Lumen Blood
H+ +
C.A.
CO2+ H
2O
Proximal Tubule-Early
Na+
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K+
Lumen Blood
H+ K+
H Anion Cl-
Anion- Na+
Na+
H Anion
Cl-
Proximal Tubule-Late
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K+
K+
Lumen Blood
K+
Cl-
Na+
Na+
K+Cl-
K+
Thick Ascending Limb
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K+
K+
Lumen Blood
K+
Cl-
Na+
Na+
Cl-
Distal Convoluted Tubule
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K+
K+
Lumen Blood
Aldosterone
Aldo Receptor
Na+
Na+
Collecting Tubule (Duct)
Principal Cell
K+
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Tubulo-glomerular Feedback
Distinct from glomerular-tubular balance
NaCl delivery to macula densa of thick
ascending limb of Henle regulatesafferent arteriolar resistance (increased
delivery causes constriction and
decreased delivery causes dilation) Minute-to-minute regulation of delivery
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200
150
GFR
100
50
2 4 6 8
Hours
Protein load
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Afferent arterioleGFR
NaCl
delivery
Macula
Densa
PCT
Thick
Ascending
Limb
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