Neurotransmitter binding to synapse receptors reduces membrane voltage, which spreads to axon hillock. When membrane voltage reaches threshold at axon hillock, cell membrane has large and rapid voltage change {spike, axon}| [Koch, 1999] [Salinas and Sejnowski, 2001] [Softky, 1995].
level
Spike voltage rises from -70 mV to +5 mV in 0.5 millisecond and then falls back to -70 mV in 0.5 millisecond.
time
Depolarizations have short duration, allowing precise time and time-interval coordination and comparison.
strength
Depolarizations have same strengths and time intervals. Depolarization prevents nerve-signal deterioration with distance and time, allowing axons to be long and act over long time intervals. Neurons can thus be anywhere and have any pattern.
threshold
Threshold can vary, between -50 mV and -30 mV.
Depolarization makes neurons act like switches. Threshold keeps neurons off until they switch on. Rapid recovery makes them switch off.
Computers are switching networks and can change switch thresholds.
Switches can contain messages in binary code [Adrian, 1980].
travel
Depolarization brings adjacent cell membrane to threshold, causing adjacent spike. That spike, in turn, causes adjacent cell membrane to reach threshold, causing adjacent spike. Spikes travel along axon from axon hillock to synapse.
direction
Spikes cannot go backward because cell membrane takes time to recover from spike. Ions at previous-spike cell membrane have low concentration and do not flow across membrane.
rate
Axons can sustain up to 800 spikes per second. Spikes cannot repeat faster at a cell-membrane location, because cell membrane takes 0.5-millisecond refractory period to recover from a spike.
factors
Axon hillocks do not distinguish neurotransmitters, receptors, or input patterns. All things that effect membrane voltage merely add.
Biological Sciences>Zoology>Organ>Nerve>Neuron>Physiology
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Date Modified: 2022.0224