 Stress , to a physiologist , means any situation that threatens the continued stability of the body and its functions . Stress affects a wide variety of body systems : the two most consistently activated are the hypothalamic @-@ pituitary @-@ adrenal axis and the norepinephrine system , including both the sympathetic nervous system and the locus coeruleus @-@ centered system in the brain . <unk> of many types evoke increases in noradrenergic activity , which mobilizes the brain and body to meet the threat . Chronic stress , if continued for a long time , can damage many parts of the body . A significant part of the damage is due to the effects of sustained norepinephrine release , because of norepinephrine 's general function of directing resources away from maintenance , regeneration , and reproduction , and toward systems that are required for active movement . The consequences can include slowing of growth ( in children ) , sleeplessness , loss of libido , gastrointestinal problems , impaired disease resistance , slower rates of injury healing , depression , and increased vulnerability to addiction . 
