During the Flexion Phase, what happens to the sacral base?

During the Flexion Phase, what happens to the sacral base?

• A. Moves anterior
• B. Moves posterior
• C. No movement
• D. Rotates

Answer: (B)

During the flexion phase of the cranial rhythmic impulse, the occiput flexes while the sacrum moves in the opposite direction. The sacral base moves posteriorly (sacral counternutation), and the apex moves anteriorly. This posterior shift of the base fits the flexion phase, whereas moving the base forward would indicate nutation, which is the opposite, associated with the extension phase.

During the flexion phase of the cranial rhythmic impulse, the occiput flexes while the sacrum moves in the opposite direction. The sacral base moves posteriorly (sacral counternutation), and the apex moves anteriorly. This posterior shift of the base fits the flexion phase, whereas moving the base forward would indicate nutation, which is the opposite, associated with the extension phase.