As the creator of the “performance“ that is your lecture, you have the copyright on the content. It does not become a copyright issue until the lecture is fixed in some tangible form, is communicated or broadcasted. The copyright in a recording of your lecture would belong to you. The interpretive class notes of a student would not, assuming they were not a verbatim record. The ideas in your lecture are not protected by copyright, but the fixation of the performance of the lecture would be.
A faculty member owns the copyright in course notes, PowerPoints and other unpublished material that are created and used for their courses. Permission would be required for another instructor to use the materials or for students to post such materials on public websites.