HMB200H1 Chapter Notes - Chapter 4.2: Sodium Channel, Threshold Potential, Resting Potential
Document Summary
Action potential: brief but larger reversal in membrane polarity, lasting about 1 millisecond. Large concentration of n= ions in (depolarize) Large concentrations of k+ ions out (hyperpolarize) The combined flow of na and k creates the action potential. Threshold potential: membrane voltage undergoes drastic change w/ no further stimulation. Once neuron passes this potential, no further stimulation from other neurons are needed to complete the action potential. Hyperpolarization (k+ ions rush out lowers the voltage) Voltage-sensitive channels: closed when axon membrane is at resting potential. There"s a limit to how frequently action potentials can occur: due to na+ and k+ channels. Absolute refractory: during depolarization & repolarization another action potential cannot occur. Relative refractory: during hyperpolarization, another action potential can occur: stimulation must be more intense than what induced the first action potential. Result from ion channel structure: na+ has 2 gates, k+ has 1 gate. Resting potential gate 1 is closed, gate 2 is open.
