intracellular fluid
67%
plasma
extracellular
fluid
26%
7%
water
Na+
K+
Clsugars
proteins
nucleus
cytoplasm
Definitions
•
•
•
•
•
•
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Solute
Solvent
Osmosis
Osmotic Pressure
Osmolarity
Hyperosmotic
Hypoosmotic
Solutes are dissolved particles in
solution (any type)
• Osmotic pressure depends on the number of solutes/unit
volume (rather than chemical nature of solutes)
Osmotic flux of water:
--which way will the water move?
-- Why is there net water flux tothe right?
As this column rises higher, it will
exert increasing pressure. At some
point that hydrostatic pressure will
reach an equilibrium, at which point
no more net water will move across the
semi-permeable membrane.
This pressure is the ‘osmotic pressure’
of the starting solution on the right.
Solutes are dissolved particles in
solution (any type)
isosmotic
(osmotic pressure is equal)
Solutes are dissolved particles in
solution (any type)
hypersmotic
(higher osmotic pressure)
hyposmotic
(lower osmotic pressure)
Water always moves from an area of low osmotic
pressure to an area of high osmotic pressure
osmotic pressure: the pressure of
water to enter, given the solute
concentration
Hyposmotic (lower
osmotic pressure)
Hyperosmotic (higher
osmotic pressure)
Osmosis: movement of water from an
Area with lower osmotic pressure to
Higher osmotic pressure
Osmotic pressures are generally
described in osmolar units:
Osmolarity
= concentration of solutes in a solution
Osmolarity vs. Molarity:
150 mMol sucrose = 150 mOsm sucrose
150 mMol NaCl
= 300 mOsm NaCl
Definitions
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Solute: Dissolved particles in a solution
Solvent: What the particles are dissolved in
movement of water from an area with lower
Osmosis: osmotic pressure to higher osmotic pressure
Osmotic Pressure: the pressure of water to enter, given
the solute concentration
Osmolarity: Concentration of solutes in a solution
Hyperosmotic: Higher osmotic pressure
Hypoosmotic: Lower osmotic pressure
The Mammalian Kidney
Active movement of Na+
Passive movement of water
Distal tubule
Proximal tubule
LOW
Collecting
duct
Bowman’s
capsule
Na+
glomerulus
H2O
To bladder
Extracellular
Na+ conc.
Loop of Henle
HIGH
What it actually looks like
Distal tubule
Proximal tubule
Bowman’s capsule
glomerulus
Collecting duct
Loop of Henle
Hypovolemia
Osmotic Imbalance
Causing an increase in
secretion and release
of VP
Baroreceptors
in arteries of the heart
VP
2 major effects:
1. Vasoconstriction
2. Water retention in kidney
Passive movement of water
Proximal tubule
Distal tubule
Collecting
duct
Bowman’s
capsule
glomerulus
H2
O
To bladder
Loop of Henle
The water pore is a protein called:
aquaporin 2 (AQP2)
Collecting Duct Cell
n
Collecting Duct:
n
filtrate
Extracellular space
Lower Na+
Basal side of cell
apical side
of cell
Higher Na+
to bladder
Collecting Duct:
n
n
H2O
Lower Na+
basal aquaporins
H2O
Aquaporin 2
No Vasopressin:
Add Vasopressin:
H2O
Higher Na+
to bladder
Collecting Duct:
n
n
H2O
Lower Na+
basal aquaporins
H2O
Aquaporin 2
Add Vasopressin:
H2O
Higher Na+
to bladder
Collecting Duct Cross-Section
Cells labeled with fluorescent antibodies made to the water channel
n
Collecting Duct:
n
Collecting Duct:
Collecting Duct:
Stain for aquaporin 2 (no vasopressin):
Collecting Duct:
Stain for aquaporin 2 (no vasopressin):
Add Vasopressin:
Collecting Duct:
Stain for aquaporin 2:
Add Vasopressin:
Collecting Duct:
Vasopressin and Osmolality
2 major effects of vasopressin:
1. Vasoconstriction
2. Water retention in kidney:
V1a receptor
V2 receptor
Smooth muscle cell
In arteries/capillaries
Collecting Duct Cell
VP
DAG
PLC
Gq
IP3
V1a receptor: localized
to vascular smooth
muscle cells
V2 receptor: localized to the kidney
Pathophysiology of Osmoregulatory
processes
• Diabetes Insipidus
– Two types:
• Neurogenic DI:
• Nephrogenic DI:
Neurogenic Diabetes Insipidus
VP is made but not
transported
VP
1. no VP is secreted
2. Very little water is retained in the collecting duct
Treatment with VP
can alleviate the
problem
Nephrogenic Diabetes Insipidus
Collecting Duct Cell
Vasopressin is
synthesized and
secreted normally
VP
But there is a defect in the cellular mechanism that responds to VP
Pathophysiology of Osmoregulatory
processes
• Diabetes Insipidus
– Two types:
• Neurogenic DI: Problem with VP secretion
• Nephrogenic DI: Problem with VP receptors in collecting duct
Hypothalamus
Posterior
Pituitary
A
B
C