Neurons are enclosed in semipermeable membranes. Protein pumps and channels direct electrochemical forces which move sodium, potassium, and chloride ions (with charges of +1, +1, and -1 respectively) through this membrane.
At rest, sodium-potassium pumps use energy to move sodium ions out and potassium ions in (at a ratio of 3 to 2) each against their concentration gradient creating a resting galvanic potential effected by ionic intracellular and extracellular concentrations.
When a neuron is triggered, sodium and potassium channels allow ion movement driven by electrical and concentration driving forces. Sodium channels open first, allowing sodium ions to flow in, then potassium channels open allowing potassium ions to flow out. Within a few milliseconds, the process ends and the neuron returns to its resting state.
This neural activation causes a minute spike in ion flux which contributes to triggering (or inhibiting) associated neurons and can be measured locally with sensitive electromagnetic field sensing instrumentation.
You can learn more about neurons in this teacher’s guide by the National Institute of Health. This video is good too 2-Minute Neuroscience: The Neuron.