KP222 Lecture 8: KP222 Lecture 8
31 Jan 2019
School
Department
Course
Professor
Document Summary
Graded depolarization of axon hillock large enough to change resting potential (10-15mv) (-70mv) to threshold level of voltage-gated sodium channels (-55mv) Wave o electrical current moves down axon. Ap occurs from ion movement across neutron membrane. But not many ions actually move across the membrane during each ap. Therefore, the relative concentrations of na+ and k+ inside and outside remain relatively unchanged. 1 in every 100,000 k+ leaves cell to shift the membrane potential from +30 to -70 mv. Given that na+ channels opened in response to depolarization, why do they close when cell is still depolarized. Inactivation gates respond to depolarization but with a 0. 5 sec delay. No matter how large the stimulus from graded potential. Strength of graded potential initiation ap has no in uence on amplitude of the. Ap is either triggered or not this is the key! Membrane cannot produce another ap because na+ channels are inactivated. Limits the rate of spike frequency (rate coding)
