At the 28th Annual Distance Learning and Teaching Conference, the keynoter James Zull reported that there are "emotional chemicals" in the brain that impact our learning.
First, when we learn something there is a positive chemical reaction that both makes us feel good for having learned something, but also the chemical (dopamine) enhances our ability to learn even more.
Second, we as teachers can and do affect the chemical reactions in our students' brains. When we put pressure or stress our students, that increases their adrenalin and it shuts down their learning. When we create a positive "safe' learning environment we stimulate serotonin that allows the rationale/cognitive area of the brain to function and take on the learning tasks we as teachers want them to learn.