Database schema of a like system

I've been thinking about a liking system for my website, and I can't determine the best way to approach it. I'm using MySQL, and right now, I have an activities table, for posts of text, pictures, videos, etc, and a comments table, for comments. You can like both comments and activity posts, so how should I go about with the columns of the like table? I am open to suggestions of changing the whole schema all together for a more coherent design.