startle reaction


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startle reaction

 [stahr´t'l]
the various psychophysiological phenomena, including involuntary motor and autonomic reactions, evidenced by an individual in reaction to a sudden, unexpected stimulus, as a loud noise.

star·tle re·flex

a primitive reflex response observed in the normal newborn but typically suppressed by 3-4 months of age. Any sudden stimulus (for example, a loud noise, a blow to the supporting surface, or being dropped 5-10 cm through space) causes flexion of the hip and knee joints with fanning of the fingers followed by fist clenching and extension of the upper limbs followed by flexion. Synonym(s): Moro reflex, parachute reflex, startle reaction
See also: cochleopalpebral reflex.
References in periodicals archive ?
Valls-Sole, "Excitability of the pathways mediating the startle reaction before execution of a voluntary movement," Experimental Brain Research, vol.
Nobbe, "Habituation of the auditory startle reaction is reduced during preparation for execution of a motor task in normal human subjects," Brain Research, vol.
Subjects had little success in squelching their responses to the gunshot and also had problems simulating a startle reaction.
With emotions such as surprise, happiness and disgust, note the researchers, facial expressions can be inhibited and simulated fairly successfully and are far more difficult to elicit experimentally than is the startle reaction.
This familiarity and comfort carries over into your ability to control your startle reactions.