This learning model is currently available in English.
Explore the system
From input to output
Trace dendrites → cell body → axon → axon terminal. Myelin wraps the axon; the signal travels along it.
Sources and model limits
Original schematic. Positions show relationships; structures and concentrations are not to scale.
- Julien's Primer of Drug Action · 15 · 2 · From input to output · PDF 22 · 2.1
- Professor deck 2 · Neuron and action potential · PDF 10, 11, 12, 15, 18
Course notes and existing practice
Learning objective
Describe the all-or-none action potential and distinguish its propagation from transmitter release at a terminal.
A threshold-triggered electrical event
The course’s graph shows resting potential, threshold, depolarization, repolarization, hyperpolarization, and a refractory period. All-or-none means an action potential is triggered when the required threshold is reached; a below-threshold change is not a smaller action potential. The graph is an introductory illustration, not a universal numerical template for every neuron.
Propagation and the terminal
The axon diagram shows local sodium entry depolarizing an adjacent region enough to open voltage-gated sodium channels there, recreating the event along the axon. The terminal is where this electrical arrival can lead to calcium entry and transmitter release. Electrical propagation along the axon and chemical transmission across a synapse are distinct parts of the explanation.
- Action potential
- A threshold-triggered, all-or-none electrical event that propagates along an axon in the course model.
- Depolarization
- A change toward a less negative membrane potential in the illustrated action-potential cycle.
- Refractory period
- The recovery interval associated with the action-potential cycle.
Professor deck 2, PDF pages 10, 11, 12. Explanation and terminology are paraphrased course material. Examples and study prompts are original, unscored teaching aids. Source conformance is separate from scientific or clinical review.
Worked examples are original instructional illustrations; they are not professor quotations or exam requirements.