is an excessive response to stimuli
. Irritability takes many forms, from the contraction
of a unicellular organism
when touched, to complex reactions involving all the senses of higher animals
. In plants
, response is usually different from that seen in animals, but is nonetheless present. The term irritability is used for both the physiological
reaction to stimuli and for the pathological
, abnormal or excessive sensitivity to stimuli.
Irritability may manifest in behavioral responses to both physiological as well as behavioral stimuli, including environmental, situational, sociological, and emotional stimuli.
when not of the usual physiological response is a symptom in a variety of conditions, including: