Dysautonomia (or autonomic dysfunction) is any disease or malfunction of the autonomic nervous system (ANS). The autonomic nervous system controls a number of functions in the body, such as heart rate, blood pressure, digestive tract peristalsis, and sweating, amongst others. Dysfunction of the ANS can involve any of these functions. A number of conditions are forms of dysautonomia: postural orthostatic tachycardia syndrome (POTS), inappropriate sinus tachycardia (IST), vasovagal syncope, pure autonomic failure, neurocardiogenic syncope (NCS), neurally mediated hypotension (NMH), orthostatic hypotension, orthostatic hypertension, autonomic instability, and a number of lesser-known disorders such as cerebral salt-wasting syndrome.