The Pericardium is an membrane surrounding the Heart. It's main function is to project and maintain the Heart. As a protector, it guards against any External Pernicious invasion to the inner part of the Heart. Out of the 6 major Pernicious Elements, the main concerned one here for the Pericardium is Heat. If it is attacked by pathogenic Heat, it can cause high fever, coma and red tongue.
Physiologically speaking, it also assists the Heart to communicate with the rest of body. Together with the Heart, it houses the Mind (Shen -神 ). In case of the Pericardium Blood Deficiency, depression and slight anxiety can appear. Blood Heat in Pericardium can lead to anxiety, insomnia and agitation. Phlegm in the Pericardium can cause mental confusion and, mental illness if it is serious.