According to Yoga, spine is the place for mental concentration where shat chakras exist within the Sushumna Nadi (nerve). It has been named Hridaya in the Yogic scriptures. Literal meaning of Hridaya is the central part. The Sushumana Nadi in spine is the central part of body. Therefore, it is defined as Hridaya.
In the Yogic scriptures wherever the word Hridaya is mentioned or sadhakas are told to concentrate in Hridaya it refers to the concentration of consciousness / mind only in the Sushumna. In a book, Yoga Swarodya, it is mentioned that Sushumna Nadi where all the chakras are situated is the only Hridaya and it is unanimously accepted in all the scriptures. A physical thing (heart) is not the Hridaya as understood by many.
Therefore, sadhaka of Yoga should consider the Sushumna Nadi only as the Hridaya instead of heart. We can say that the creation of the shat-chakras, is the science of body based on the intuitive knowledge of experienced Yogis. With the constant practice of meditation on these chakras one can attain the higher planes of Yoga and Spiritualism.