Concen np solute in cell > concen np solute in solution solution hypotonic & cell swellsconcen np solute in cell < concen np solute in solution solution hypertonic & cell shrhinksconcen np solute in cell = concen np solute in solution solution isotonic & no net movement Pg. 159 chart Law of conservation of electrical charge ? net amount of electrical charge produced in any process is zero; human body is electrically neutral Separating pos charges from neg charges requires energy If separated pos and neg charges can move freely toward each other, material through which they are moving is a conductor (i.e. water). If separated charges unable to move through material that separates them, material is an insulator Input of energy to transport ions across membrane creates electrical gradient Electrochemical gradient ? combination of electrical and concentration gradients Resting membrane potential difference (membrane potential) ? electrical gradient between ECF and ICFvoltmeter ? measures diff in electrical charge btwn inside of cell & surrounding solution; uses two electrodes, the ground/reference electrode in solution & a recording electrode inside cell Equilibrium potential ? memb potential that exactly opposes the concentration gradient of the ion; measured by Nernst e q (1 ion) or Goldman eq (1+ ions) Na+-K+-ATPase called an electrogenic pump b/c it helps maintain electrical gradient Factors influencing memb potential Concentration gradients of diff ions across membrane Permeability of memb to those ions Depolarized ? describes when memb potential becomes more pos (less neg) Repolarized ? describes a return to resting memb potential [after depolarization] Hyperpolarized ? descries when memb potential becomes more neg Beta cell of pancreases, releases insulin(a) at rest low glucose levels in blood metabolism slows ATP decr ATP-gated K+ channel opens cell at resting memb pot; no insulin released(b) secreting insult high glucose levels in blood metabolism incr ATP incr K+ channel closes depolarization & voltage-gated Ca2+ channels open Ca2+ entry triggers exocytosis, insulin released
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