Demoted from Silver 5 to Bronze 1?

You can, but you would need to lose so many games, that your MMR dropped to B5 levels.

This seems almost not doable.

You can get demoted tiers by having an mmr comparable to that of division 5 of the tier below.

So if you lose enough games at S5 such that you find yourself getting matchmade with bronze 4's, theres a pretty good chance that further losses could potentially demote you to bronze 1.

LOL sadly this happened to me I went from s2 to s4 to b2 to b1 to b3 to s4 and climbing again. So my elo dropped so much I was b4 at 1 point???:((((

lost a lot.