The cobra is the first of three backward bends, which come after the sitting forward bend in our series.
Swami Vishnudevananda on the cobra:
Raise the head and upper portion of the body slowly, just as the cobra raises its hood. Roll back the spine slowly so that you can actually feel the bending of the vertebrae one by one and the pressure trrvelling downward from the cervical, dorsal and lumbar regions and lastly to the sacral regions.
Gheranda Samhita (one of the three classic texts of hatha yoga, 17th century) on the cobra:
This always increases bodily heat, destroys all diseases, and by the practice of this posture the kundalini awakens.
The cobra is the first of three backward bends. They are followed by the spinal twist.