Lecture notes for Friday, April 13, 2018 Functions of Membrane Voltages: 1) Oocyte fast block to polyspermy. 2) Muscle cell contraction stimulation/coordination. 3) Nerve impulses. 4) Stimulation of secretion of cytoplasmic vesicles. (For example synaptic vesicles, cortical granules) 5) Fish pigment cell response to cell-cell contact. #) Paramecia reversal of direction cilia power stroke Do the cilia in our throats and lungs reverse direction?) ?) Galvanotactic guidance of crawling cells? ?) Stimulation / Inhibition of bone formation / breakdown? Stimulation of wound healing??? ------------------------------------------------------- If it is true that as much as a third of our ATP energy gets used by the Sodium Pump enzyme pumping potassium, into cells & pumping sodium out, many functions are probably being accomplished. (Most of these functions haven't been discovered yet? ) Fast coordination at relatively long range By what experimental criteria could you discover these not-yet-discovered coordination mechanisms, that work by changes in leakage of sodium, and/or potassium, and/or calcium through plasma membranes? Disturbed by higher extracellular potassium concentrations? Disturbed by artificial electric voltage fields? ------------------------------------ How can voltage fields be generated? Ion pumping by epithelial cell sheets Piezoelectric effect (can only produce AC alternating current, not a steady voltage in the same direction). Crystals that lack inversion symmetry can often produce temporary voltages when squeezed, stretched or twisted, (Because distortion produces a net movement of positive and/or negative ions). Half of crystal structures lack inversion symmetry. Electroosmosis. If you squeeze a piece of cartilage, water will be forced out of it, and will carry positive counter-ions out along with the water. This will create a temporary electrical voltage. (Think of voltages as electrical pressures, what matters is difference in voltage from one location to another) which will be positive wherever the water flows, and negative at those locations away from which the water moved. This voltage will leak away in a few seconds: It is always only very temporary. Squeezing wet clay will also produce an electroosmotic voltage, to the extent that the solid component has negative voltages, so that the counter-ions dissolved in the water will be predominantly positive. If you had some material with positively charged solids, then its counter-ions would be predominantly negative (like chlorides instead of sodium ions) when squeezing that material would produce a net negative charge where the water flowed. Many scientists have reported that they have detected piezoelectric voltages produced by bone, collagen, DNA and by other biological substances. When I asked several of them "How can you be sure that the voltages that you measured were piezoelectric, instead of electroosmotic" their answers were "What is electroosmosis?" If they detect a voltage being produced as a result of squeezing or stretching any material, they assume that the cause must have been piezoelectric, which they don't realize results specifically from crystal structure.