The Startle Reflex and Glycine

The startle reflex is a natural response that protects us from sudden threats. However, an exaggerated or easily triggered startle reflex may indicate an underlying issue. Startling too easily could be a sign of a problem. The neurobiology of the startle reflex involves visual, auditory, and tactile inputs, with most research focusing on the auditory aspect. The reflex is enhanced by fear and anxiety, while pleasure inhibits it. Loud noise, bright light, and female sex hormones can also enhance the startle reflex. Sensory inputs are integrated in the brainstem, and the motor response is coordinated in the spinal cord. Glutamate activates the startle reflex, but it is inhibited by GABA in the brainstem and glycine in the spinal cord.