Aside from the actual logs (eastern red cedar) I seriously doubt that the rest of the building is authentic to 1840. For incidence, I doubt that a slave cabin in Tennessee would have had a wood floor. Most of the cabins I've seen around here that still exist have dirt floors.
The huts the Irish were driven out of during the potato famine, when they couldn't pay the rent, were probably inferior to the average slave cabin...but at least the residents were free.