excitation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or process of exciting or an instance of it.
• noun The state or condition of being excited.
• noun Physiology The activity produced in an organ, tissue, or part, such as a nerve cell, as a result of stimulation.

from The Century Dictionary.

• noun The act of exciting or rousing to action; a stirring up or awakening.
• noun The state of being excited; excitement.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of exciting or putting in motion; the act of rousing up or awakening.
• noun (Physiol.) The act of producing excitement (stimulation); also, the excitement produced.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of exciting or putting in motion; the act of rousing up or awakening.
• noun The act of producing excitement (stimulation); also, the excitement produced.
• noun physiology The activity produced in an organ, tissue, or part, such as a nerve cell, as a result of stimulation
• noun physics The change in state as an excited state is formed by the absorption of a quantum of energy

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the state of being emotionally aroused and worked up
• noun the neural or electrical arousal of an organ or muscle or gland
• noun something that agitates and arouses