nucleus cytoplasm extracellular fluid water Na+ K+ Cl- sugars proteins plasma intracellular fluid 7% 26% 67%

Definitions 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)

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. Osmotic flux of water: --which way will the water move? -- Why is there net water flux tothe right?

isosmotic Solutes are dissolved particles in solution (any type) (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 Hyposmotic (lower osmotic pressure) Hyperosmotic (higher osmotic pressure) osmotic pressure: the pressure of water to enter, given the solute concentration Osmosis: movement of water from an Area with lower osmotic pressure to Higher osmotic pressure

Osmolarity = concentration of solutes in a solution Osmolarity vs. Molarity: 150 mMol sucrose= 150 mOsm sucrose 150 mMol NaCl= 300 mOsm NaCl Osmotic pressures are generally described in osmolar units:

Definitions Solute: Solvent: Osmosis: Osmotic Pressure: Osmolarity: Hyperosmotic: Hypoosmotic: Dissolved particles in a solution movement of water from an area with lower osmotic pressure to higher osmotic pressure the pressure of water to enter, given the solute concentration Concentration of solutes in a solution Higher osmotic pressure Lower osmotic pressure What the particles are dissolved in

The Mammalian Kidney glomerulus Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct To bladder Extracellular Na+ conc. Passive movement of water H2OH2O Active movement of Na+ Na+ HIGH LOW

What it actually looks like Bowman’s capsule Distal tubule Proximal tubule Loop of Henle glomerulus Collecting duct

Osmotic ImbalanceHypovolemia

Baroreceptors in arteries of the heart Causing an increase in secretion and release of VP VP 2 major effects: 1.Vasoconstriction 2.Water retention in kidney

Collecting Duct Cell glomerulus Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct To bladder Passive movement of water H2OH2O The water pore is a protein called: aquaporin 2 (AQP2)

Collecting Duct: nn filtrate to bladder Basal side of cell apical side of cell Lower Na+ Higher Na+ Extracellular space

Collecting Duct: nn to bladder Lower Na+ Higher Na+ No Vasopressin: basal aquaporins Aquaporin 2 H2OH2O H2OH2O H2OH2O Add Vasopressin:

Collecting Duct: nn to bladder Lower Na+ Higher Na+ basal aquaporins Aquaporin 2 H2OH2O H2OH2O H2OH2O Add Vasopressin:

Collecting Duct Cross-Section Cells labeled with fluorescent antibodies made to the water channel

nn 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: Collecting Duct Cell V2 receptor: localized to the kidney VP Gq PLC IP3 DAG Smooth muscle cell In arteries/capillaries V1a receptor: localized to vascular smooth muscle cells V1a receptor V2 receptor

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 VP Vasopressin is synthesized and secreted normally Collecting Duct Cell 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

ABC Hypothalamus Posterior Pituitary