NROC61H3 Lecture Notes - Channelopathy, Oligodendrocyte, Axon Hillock
The frequency and pattern of action potentials constitute the code used by neurons to transfer information from one location to another. The ups and downs of an action potential: see fig. 4. 1: the first part, called the rising phase, is characterized by a rapid depolarization of the membrane. Na+ ions enter the fiber through these channels: the entry of na+ depolarizes the membrane (i. e. the cytosolic surface of the membrane becomes negative) If this depolarization (generator potential) achieves a critical level, the membrane will generate an action potential. The critical level of depolarization that must be crossed in order to trigger an action potential is called threshold: the depolarization that causes action potentials arises in different ways in different neurons. The generation of multiple action potentials: the rate of action potential generation depends on the magnitude of the continuous depolarizing current, the firing frequency of action potentials reflects the magnitude of the depolarizing current.