The fundamental unit of the nervous system is the neuron. The resting membrane potential is determined by intracellular and extracellular ion concentrations, modeled mathematically by the Nernst equation for a single ion: $$E_{eq} = \frac{RT}{zF} \ln\left(\frac{[X]_{out}}{[X]_{in}}\right)$$ where $R$ is the gas constant, $T$ is temperature, $z$ is valence, and $F$ is Faraday's constant.

Synaptic transmission relies on chemical messengers. Glutamate is the primary excitatory neurotransmitter in the CNS, whereas GABA (Gamma-aminobutyric acid) is the primary inhibitory neurotransmitter. Modulatory transmitters like dopamine and serotonin regulate complex behaviors including reward, mood, and arousal.