Emotional stress is often associated with auditory phenomena such as hyperacusis, tinnitus, Ménière's disease and vertigo. Stress develops as a result of a person's attempts to come to terms with the increased or unexpected demands of his or her environment. Stress serves to protect one from physical danger and to temporarily increase one's performance in order to increase the probability of survival. Sleep and appetite are particularly reduced, while anxiety increases. The mental changes induced by stress may contribute to the onset or exacerbation of tinnitus. The following links exist between the auditory and stress systems: the limbic system, which regulates instinctive behavior and emotions, is linked to the auditory system via the medial geniculate body (amygdala). The hypothalamus, which is the integrative center of the endocrine and autonomic systems, is linked to the auditory system via the inferior colliculus. The reticular system, which is focused on the behavior pattern of attention and excitement, projects serotonergic fibers to all pathways of the auditory system, ranging from the cochlea to the auditory cortex.