Excitable means easily roused into strong feeling. It does not take much, and everybody knows it.
It describes people, dogs and crowds, and it is faintly patronising when used about adults, since calling somebody excitable suggests their reactions are out of proportion. Applied to a puppy it is simply accurate. Medicine and physiology use it precisely for tissue that responds to stimulation, so excitable cells is a technical term. The noun is excitability, and the verb excite covers both the everyday and the technical.
1adjectiveexcitableEasily made excited or upset.
“He is an excitable child and needs a calm routine.”
Proto-Indo-European
*keyh₂-
Latin
excitō — to call out, call forth, arouse, wake up, stimulate
Old French
exciter
Middle English
exciten
English
excite
English, today
excitable
Built from
From excite + -able. excite comes from Middle English exciten, from Old French exciter, from Latin excitō (“to call out, call forth, arouse, wake up, stimulate”), frequentative of excieō (“to call out, arouse, excite”), from ex (“out”) + cieō (“to call, summon”). See cite and compare to accite, concite, incite.
Etymology from Wiktionary, CC BY-SA