Action Potentials (A/P)

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Action potentials (A/P) are specific electrical signals or impulses — mechanisms for communication generated by neurons — essential to sensory processing throughout the nervous system. When a stimulated neuron triggers an A/P in the A/P trigger zone, the A/P signal travels along the axon to the axon terminal. There it transmits information across the synapse (gap between neurons) to the receiving neuron and up the chain to the brain. More specifically, the triggered A/P reaches the presynaptic (before the synapse) neuron and causes the electric signal to convert (a process called transduction) to a chemical signal (neurotransmitter). The neurotransmitter crosses the synapse to reach the postsynaptic (after the synapse) neuron. Also see Potentials, Excitatory or Inhibitory Synapses, Generator Potentials, and Nerves. How an A/P works in the auditory system:

• A sensory stimulus (loud noise) reaches sensory (auditory) receptors, which transmit their own A/Ps (auditory signals) to the central nervous system (CNS). The brain interprets the electrical activity as (auditory) stimuli.
• The rate of A/Ps produced by auditory receptors can contain (encode) the stimulus intensity of the sensory stimuli (very loud noise), making it more likely the brain will respond.