[Pain--from the physiological and internal medicine viewpoint].

Physiology of pain is a manifold and very complex phenomenon that is far from being understood. It cannot be explained without reference to psychosocial conditions. Pain has the function of a warning system, but the system is far from perfect, because a number of chronic diseases (e.g., arterial hypertension or malignant neoplasms) begin slowly and nearly painless. The role of pain in internal medicine will be exemplified by thoracic and abdominal pain. With regard to diagnoses both types of pain represent ambiguous symptoms. Their anatomic and physiologic substrates often cannot be ascertained completely by anamnestic means (according to localization, quality, trigger factors, time structure, and concomitant symptoms of pain). Visceral pain is regularly characterized by the phenomenon of the so-called "transferred pain": that means that the perception of pain is not restricted to the place of its origin but is also found in distant regions of the body, primarily in well defined dermatomes ("Head's areas"). This makes the differential diagnosis of internal diseases very difficult because of the parallel connection of nociceptive afferences from the skin and deeper-seated strata on identical spinal segments. Statements according to the pharmacotherapeutic aspects of pain primarily focus on the causal therapy of the prethoracic pain. In this regard differential-therapeutic aspects of angina pectoris, pericarditis, pleurisy, gastro-esophageal reflux, and vertebragenic, myogenic, and neurogenic disturbances are well to the fore.