Irritability is the excitatory ability that living organisms have to respond to changes in their environment.The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli. It is usually used to refer to anger or frustration. In individuals with autism disorder for example, they tend to be marked by aggression patterns.Irritability can be a growing response to the objective stimuli of hunger or thirst in animals or humans which then reaches some level of awareness of that need. Irritability may be demonstrated in behavioral responses to both physiological and behavioral stimuli including environmental, situational, sociological, and emotional stimuli.The emotion, anger, also known as wrath or rage, is an intense emotional state. It involves a strong uncomfortable and hostile response to a perceived provocation, hurt or threat.A person experiencing anger will often experience physical conditions, such as increased heart rate, elevated blood pressure, and increased levels of adrenaline and noradrenaline.Some view anger as an emotion which triggers part of the fight or flight brain response. Anger becomes the predominant feeling behaviorally, cognitively, and physiologically when a person makes the conscious choice to take action to immediately stop the threatening behavior of another outside force.The English term originally comes from the term anger of Old Norse language.Anger can have many physical and mental consequences. The external expression of anger can be found in facial expressions, body language, physiological responses, and at times public acts of aggression. Facial expressions can range from inward angling of the eyebrows to a full frown. While most of those who experience anger explain its arousal as a result of 'what has happened to them,' psychologists point out that an angry person can very well be mistaken because anger causes a loss in self-monitoring capacity and objective observability.Modern psychologists view anger as a primary, natural, and mature emotion experienced by virtually all humans at times, and as something that has functional value for survival. Uncontrolled anger can, however, negatively affect personal or social well-being and impact negatively on those around them. While many philosophers and writers have warned against the spontaneous and uncontrolled fits of anger, there has been disagreement over the intrinsic value of anger. The issue of dealing with anger has been written about since the times of the earliest philosophers, but modern psychologists, in contrast to earlier writers, have also pointed out the possible harmful effects of suppressing anger.Mind