Anodea Judith (1996: p.5) provides a modern interpretation of the chakras:

A chakra is a center of activity that receives, assimilates, and expresses life force energy. The word chakra literally translates as wheel or disc and refers to a spinning sphere of bioenergetic activity emanating from the major nerve ganglia branching forward from the spinal column. There are six of these wheels stacked in a column of energy that spans from the base of the spine to the middle of the forehead. And the seventh which is beyond the physical region. It is the six major chakras that correlate with basic states of consciousness...

Susan Shumsky (2003, p. 24) supports this idea:

Each chakra in your spinal column is believed to influence or even govern bodily functions near its region of the spine. Because autopsies do not reveal chakras, most people think they are a fancy of fertile imagination. Yet their existence is well documented in the traditions of the far east...

Chakras, as described above, are energy centers along the spine located at major branchings of the human nervous system, beginning at the base of the spinal column and moving upward to the top of the skull. Chakras are considered to be a point or nexus of biophysical energy or prana of the human body. Shumsky states that "prana is the basic component of your subtle body, your energy field, and the entire chakra system - the key to life and source of energy in the universe"

source - Wikipedia