Assigning public game objects to a script associated with a certain game object in a hierarchy is not updating associated prefab

In a hierarchy, I have assigned pause Button and instructional keywords to public GameObject variables ins_kws and pauseBtn in a script associated with a panel Chp9_Screen1. Now the problem is that whenever I apply changes to prefab, the associated prefab does not update. These gameobjects are not assigned to the prefab on update. However, the UI panel in hierarchy and prefab in project are linked with each other. Please help me resolve this issue. I do not want to create prefabs of pasueBtn and ins_kws and assign them to prefab Chp9_Screen1 please. Why can not the prefab update with these game Objects?