PSY 242 Study Guide - Midterm Guide: Axon Hillock, Resting Potential, Saltatory Conduction
Document Summary
Inside the cell: more k+ and negatively charged proteins. Outside the cell: more na+ and cl- The (cid:272)ha(cid:396)ge a(cid:272)(cid:396)oss a (cid:374)eu(cid:396)o(cid:374)(cid:859)s (cid:272)ell (cid:373)e(cid:373)(cid:271)(cid:396)a(cid:374)e (cid:449)he(cid:374) the (cid:374)eu(cid:396)o(cid:374) is at (cid:396)est (usually about -70mv) Measured by placing one electrode inside the neuron (microelectrode) and one outside the neuron in extracellular fluid. Cell membrane is polarized (differently charged in two locations, outside vs. inside) Forces acting upon ions: random movement and diffusion: evenly distribute in a medium; movement down concentration gradient (high to low concentration, electrostatic pressure (electrical attraction): opposite forces attract. Potassium: diffusion pushes k+ out, negatively charged interior keeps k+ inside; potassium channels are open during resting state but few exit. Chloride: diffusion pushes cl- inside, negatively charged interior keeps cl- out. Sodium: both diffusion and negatively charged interior push na+ inside; sodium channels are closed during resting state. Continually exchanges three sodium ions inside the neuron for two potassium ions outside. Maintains balance of ions needed for proper firing.
