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Usually the onset of the startle response is a startle reflex reaction. The startle reflex is a brainstem reflectory reaction (reflex) that serves to protect vulnerable parts, such as the back of the neck (whole-body startle) and the eyes (eyeblink) and facilitates escape from sudden stimuli. It is found across many different species ...
Hyperekplexia (/ ˌ h aɪ. p ər. ɛ k ˈ p l ɛ k. s i. ə /; "exaggerated surprise") is a neurological disorder characterized by a pronounced startle response to tactile or acoustic stimuli and an ensuing period of hypertonia. The hypertonia may be predominantly truncal, attenuated during sleep, or less prominent after one year of age.
People suffering from hypervigilance may become preoccupied with scanning their environment for possible threats. They might overreact to loud and unexpected noises, exhibit an overactive startle response or become agitated in highly crowded or noisy environments. They will often have a difficult time getting to sleep or staying asleep. [7]
Fear-potentiated startle (FPS) is a reflexive physiological reaction to a presented stimulus, and is an indicator of the fear reaction in an organism. The FPS response can be elicited in the face of any threatening stimulus (e.g., any object, person or situation that would cause someone to experience feelings of fear), but it can also be elicited by a neutral stimulus as a result of fear ...
In many people with hyperacusis, an increased activity develops in the tensor tympani muscle in the middle ear as part of the startle response to some sounds. This lowered reflex threshold for tensor tympani contraction is activated by the perception/anticipation of loud sound, and is called tonic tensor tympani syndrome (TTTS).
Sudden stimuli like noise or touch to areas around the head or chest cause the startle response which will go up the brain stem and down the spinal cord causing jerk-like movements. Hyperekplexia is a heightened brainstem response where an affected person will continue to elicit the same response to a repeated stimuli. In contrast, reticular ...
Prepulse inhibition: preceding stimulus attenuates the startle response.. Prepulse inhibition (PPI) is a neurological phenomenon in which a weaker prestimulus (prepulse) inhibits the reaction of an organism to a subsequent strong reflex-eliciting stimulus (pulse), often using the startle reflex.
The majority of people with vasovagal syncope have a mixed response somewhere between these two ends of the spectrum. One account for these physiological responses is the Bezold-Jarisch reflex. Vasovagal syncope may be part of an evolved response, specifically, the fight-or-flight response. [16] [17]