The heart and kidney

The heart dominates fire, is located in the upper part of the body and belongs to yang. The kidney dominates water, is situated in the lower part of the body and belongs to yin. The relationship between the heart and kidney, therefore, concerns the balance between yin and yang, ascending and descending. Under normal physiological conditions, heart yang descends, together with the kidney yang, to warm kidney yin and kidney water. In contrast, kidney yin ascends, together with heart yin, to moisten heart yang and prevent it from becoming hyperactive. This relationship of mutual communication and restriction is called " harmony of heart and kidney. " When water and fire are in harmony, a relative balance between above and below, yin and yang, is maintained, ensuring the normal physiological function of the heart and kidney.

Once the yin - yang balance between the heart and kidney is disrupted, pathological changes will occur. For instance, when deficiency of kidney yin fails to ascend to nourish the heart, it usually leads to hyperactivity of heart yang, giving rise to such manifestations as aching back and seminal emission, with mental restlessness, palpitations, insomnia and dream - disturbed sleep, indicating " disharmony between heart and kidney. " When deficiency of kidney yang fails to evaporate fluid which then floods and ascends to depress the Function of heart yang, there may be clinical manifestations such as edema, chills, and cold limbs, accompanied by palpitations, shortness of breath and stuffiness in the chest, indicating " retained water afflicting the heart. "

The heart dominates blood and the kidney stores essence. Since essence and blood promote each other, there is a mutual causality between consumption of kidney essence and deficiency of heart blood. The heart houses the mind and the kidney essence produces marrow, which communicates with the seat of intelligence. Either deficiency of kidney essence or of heart blood, therefore, may lead to symptoms of disturbance of consciousness such as insomnia, poor memory and dream - disturbed sleep