In the case of new questions, the system doesn't automatically notify the vendors. So you can add questions, edit others, and then we recommend using the messaging feature to communicate en masse to the respondents.
But when you create a new section, that will not appear to the vendors until you approve it. Once approved, you'll be prompted to craft a short message which will be sent to the inboxes of all of your vendor Points of Contact. The vendor Points of Contact will receive an email.