Heart stores the spirit

Also heart governs the bright spirit; heart governs the spirit. This phrase comes from Plain Questions (素问 sù wèn). The heart is the seat of consciousness and mental function. If the heart fulfills its functions normally and blood and qì are abundant, the mind is lucid, alert, and responsive to the environment. If, however, the heart is diseased, the heart spirit may be disquieted, causing signs such as heart vexation, susceptibility to fright palpitation (heart palpitation due to emotional stimulus), diminished sleep, or profuse dreaming. In severe cases, there may be signs either of loss of sensibility, such as clouding sleep (hypersomnia) or coma, or of mental diseases, delirious speech, or manic agitation.