Nodding, smiling, and saying, "uh, huh" are all forms of response known as

They are all forms of supportive responses.

Supportive responses are a type of listening responses that are intended to express reassurance, understanding and/or reduce anxiety.
After the speaker has finished talking you indicate with this time of expressions how you evaluated the message.

Ongoing civil wars western roman empire finally collapsed476 c.e. romulus, the last of theroman  emperors in  the west, was overthrown by the germanic leader odoacer, who became the first barbarian to rule in rome. the order that the  roman empire  had brought towestern  europe for 1000 years was no more.