Where does excitation collide?

In physics, excitation is the raising of a system such as an atom, electron, molecule, or field from a lower energy state to a higher one, which happens when it absorbs a discrete quantum of energy. Bohr's 1913 On the constitution of atoms and molecules set out how an electron moves to a higher orbit only by absorbing a fixed amount of energy, leaving the atom in an excited state until it falls back and emits that energy again. The referent is a measurable change of energy level in matter or a field, counted in electron volts or by the frequency of the light absorbed, and it is not a nerve pushed toward firing, a leftover feeling carried into a later moment, or an input fed to a filter.[1]

Unit

One transition of a system to a higher energy level, scaled by the energy absorbed in electron volts

Recovery means

The excited state decays back to a lower level, emitting the absorbed energy as radiation

Measured by

Detected from absorption or emission spectra, with the energy read from the frequency of the light involved

In neuroscience, excitation is depolarising input that pushes a neuron toward firing an action potential, the opposite of the inhibition that holds it back. Brock, Coombs, and Eccles's 1952 The recording of potentials from motoneurones with an intracellular electrode made the first intracellular records of the excitatory postsynaptic potential, the small depolarisation a synapse produces, and whether a cell fires depends on the running balance of excitation against inhibition. The referent is an electrical drive toward firing in living nervous tissue, measured in millivolts at the membrane, and it has nothing to do with an atom absorbing a quantum, a feeling held over from an earlier event, or a driving signal in a channel.[2]

Unit

One depolarising drive toward firing, scaled by the change in membrane voltage in millivolts

Recovery means

The membrane repolarises after the input passes, and the excitatory potential decays unless firing is reached

Measured by

Recorded intracellularly as the excitatory postsynaptic potential, or inferred from firing rate and the excitation to inhibition ratio

In social psychology, excitation is the bodily arousal left over from one event that carries into and intensifies an emotional reaction to a later, unrelated one. Zillmann's 1971 Excitation transfer in communication-mediated aggressive behavior showed that arousal from an earlier source, once the person no longer attributes it to its true cause, adds to and strengthens a later feeling such as anger. The referent is residual physiological arousal misread as belonging to a new situation, measured through heart rate, skin response, and rated feeling, and it is a different thing from an atom's energy jump, a neuron's drive to fire, or an engineered input to a system.[3]

Unit

Residual arousal carried from one event into a later reaction, scaled by its lingering physiological level

Recovery means

The leftover arousal fades over time, so the transfer effect weakens as the body returns to baseline

Measured by

Indexed by physiological arousal such as heart rate and skin conductance alongside self-reported feeling and behaviour