ANSC 3301 Lecture Notes - Lecture 5: Tetraodontidae, Afterhyperpolarization, Myelin
Document Summary
Real neurons receive as many as 200,000 terminals. Size of graded potential is proportional to the intensity of the stimulus. Distance over which change in membrane potential will decrease by 63% (1/e) This constant is largest when membrane resistance is high and internal resistivity is low. The larger the length constant, the farther is propoages with distance. Membrane resistance (the difficulty with which those ions move across the membrane out of the cell) will be high with a myelin sheath which is an insulator. Larger diameter, the greater the length constant. Few k+leak channels, decreased positive charge leak out, high membrane resistance, increased propagation of action potentials, decreased decrement. K+ leak channels always open, some + charge leaks out, decreased propagation of action potentials and increased decrement. When graded potential enter, it reaches a threshold stimuli, activate voltage gated sodium channels which depolarize the cell and when the channels open it will pull the voltage towards the voltage equilibrium potential.
