Can someone explain to me how normal matchmaking works?

Tl;dr: Beware: of course this is a rant. My main question is "does playing ranked affect your normals MMR?" Along with several other related questions to matchmaking.

So I'm currently on a losing streak. When it first started, I did what I always do and took a break.

Came back, kept losing. Except when I came back, I noticed that my teammates were the definition of troll.

I would say "retarded", but you're not supposed to blame the teammates. However, the Morgana support who steals farm and then feeds and then tells me to kill myself when I politely asked her to stop isn't helping anyone (I will admit I snapped at her that game, but I couldn't tell if she was just unbearably bad or a troll).

Just like the Fizz who calls mid in champion select and then goes top after I called it, so I'm stuck mid against a Xerath while playing Quinn and my team yells at me for bot lane feeding the enemy Jinx. And not running into the unwarded jg to help them in their losing 2v4 (my team was the 2, in case that's not clear). And not saving mid tower(s) when all five members of the enemy team comes to get them. That game was totally 100% my fault, and I totally appreciated the "uninstall" "you suck" "reported" commentary throughout the entire game.

So I curiously looked up my teammates and noticed that they were all on losing streaks just like I was, and for the first time in a long time I noticed that I wasn't playing with all level 30s. Some were level 28 or whatnot. I assume someone duo queued, so that's why I was with the lower leveled players.

Usually when I play (norms) I play with silvers and golds, but now I'm back to playing with Bronze V players, whom I haven't consistently played with since December, maybe. This is a trend I noticed that started after I played ranked and got placed in Bronze I.

So is it because I started ranked that I'm stuck with the lower ranked Bronze players again? And does Rito purposefully match people on losing streaks with other people on losing streaks (because that is just cruel and unnecessary). Also, does this mean I'll have to torture myself through endless losses until I can raise my normal MMR again back to where I can play with silvers and golds? TT~TT

It's very frustrating. If all this is happening because I started ranked, then I regret playing ranked. I was happier playing normal games with people who actually knew how to play. Now it seems like every game I have a troll or an afker and everyone just blames each other when things start going wrong (not always on my team, either. Every other game, if the toxic person isn't on my team, they're on the other team, but they're still in the game).

Sigh.