Neurons are the electrically excitable cells of the nervous system. Each one collects incoming signals through branching dendrites, integrates them at the cell body (soma), and if the combined input crosses a threshold, fires an action potential that races down the axon in an all-or-nothing spike. At the far end, the signal reaches a synapse, where it triggers release of neurotransmitter molecules that diffuse across a microscopic gap to the next neuron, converting the electrical signal back into a chemical one and then back into electricity. This scene approximates that cascade: glowing spheres are neuron cell bodies, lines are dendrite/axon connections, and traveling points are propagating action potentials.

• Resting membrane potential: about −70 mV
• Action potential peak: roughly +30 to +40 mV before repolarizing
• Conduction speed: ~1 m/s (unmyelinated) up to ~120 m/s (heavily myelinated)
• Synaptic cleft width: about 20 nanometers
• Signal type: all-or-nothing spike, not graded like a dimmer switch
• Refractory period: a few milliseconds where the neuron cannot re-fire
• Human brain: ~86 billion neurons and ~100 trillion synapses
• A single neuron can connect to thousands of others via its synapses