Lecture 4 02/16/2014
Typical body of intracellular fluid 300 mOsm
Only need a change of ~1% to trigger a “thrist” sensationalso triggers homeostatic reflexes that would
absorb that water rather than releasing it to the kidneys.
150 mM = 300mOsm
Tight junctions allow water to pass (Figure 4.24)
Epithelial cells can segregate it’s proteins relative to different membranes.
Creates an imbalancesodium is concentrated in the interstitial fluid▯creates an osmotic gradient.
Water will only move if you create a way for it to move. Intracellular fluid is very different from the
Energy is expended to create an imbalance: gradients are crucial; cardiac cells secondary transport.; it also
creates a charge imbalance because the ions are charged.
Figure 4.6; charges line up along the membrane; the net flux of a charge is a current. Volts measures the
potential of a current across a membrane; measures the difference of charge across 2 things: inside the cell
relative to the outside.
70 mVcharge difference inside with respect t