Qi, Jing, and Shen in Chinese Medicine
Qi (pronounced “chee”) is generally thought of as the vital force within our bodies. Qi in its yang form is responsible for animation of the human form. Qi travels through the 12+ meridians (channels) very much like blood through vessels. Chinese medicine works to insure that Qi is able to move freely, that it is moving in the correct direction, and that there is an abundant availability of Qi. It is acquired through food, air and herbs. Qi corresponds broadly to energy and matter, and every phenomenon in the Universe is a manifestation of Qi. When Qi is condensed it can manifest matter (Yin form) and when it disperses it manifests energy (Yang). Consider Sea of Qi formula with Qi Deficiency
A quote from Chang Cai explains this concept: “Every birth is a condensation and every death is a dispersion. Birth is not a gain, death is not a loss. When condensed, the energy becomes a living being and when dispersed it is the substratum of mutations.” Qi could be likened to the String theory of quantum physics as it manifests differently depending on its vibrational quality; to simply say that "Qi is Energy" is a gross over-simplification.
Chapter twenty five in the Simple Questions contains the following quote: “A human being results from the Qi of heaven and earth. The union of the Qi of heaven and earth is called a human being”.
Essence (a Yin characteristic) is that aspect of the body that is the basis for all growth, development, and sexuality. Congenital Essence is that part of the body’s Essence that is inherited from ones parents. After birth this Essence, which is akin to an inborn constitution (DNA), determines each of our growth patterns. Congenital Essence can never be replaced if lost, but can be supplemented by acquired Essence, which is derived from food and herbs. Many of the best tonic herbs for healthy aging support the essence. It is important to maintain abundant qi through proper diet, breathing exercises and meditation, and tonic herbs so that you do not consume essence. Proper lifestyle habits, such as proper, sound sleep at night also help to preserve essence.
Essence is Yin in nature, and is the primary substance responsible for growth and development, metabolism, and plays a role in daily activity especially when Qi is depleted. Essence can be regarded as substantial Yin, and spirit, or Shen, as the counterpart Yang.
Kidney Essence produces marrow, which then produces bone marrow and then fills the spine, bone marrow and spinal cord. This is why Kidney tonics are so important in the full recovery of back injuries.
Kidney Essence rules over growth, reproduction, and development, and Kidney deficiencies can manifest as improper growth and maturation, sexual dysfunction, ED impotence, infertility, premature aging and birth defects.
The Shen represents the forces that shape our personality including mental and spiritual aspects. The Heart houses Shen and it can be observed by trained practitioners through a certain brightness of the eyes. Shen disturbances generally refer to mental disorders. While the Shen is often referred to as the spirit, it should not be confused with the Christian idea of the spirit; it is more about a person's inner light. Our Shen allows us to think and discriminate, and shapes our personality. Shen is the most immaterial of the Three Treasures in Chinese medicine.
Reference: The "Yellow Emperor's Classic of Internal Medicine-Simple Questions" (Huang Ti Nei Jing Su Wen)