What does knee jerk response mean

An immediate unthinking emotional reaction produced by an event or statement to which the reacting person is highly sensitive;When he does that the leg shoots up automatically.From the tendency of the knee to jerk involuntarily when hit sharply, properly called the patellar reflex.What's the origin of the phrase 'a knee jerk reaction'?A reflex is built into the nervous system and does not need the intervention of conscious thought to take effect.

First seen in print in 1877, it became common in the early 20th century.< back to phrase of the day.Knee jerk reaction synonyms, knee jerk reaction pronunciation, knee jerk reaction translation, english dictionary definition of knee jerk reaction.A quick and automatic response.The sum total of any particular automatic response mediated by the nervous system.