The director of the neuroscience program at my undergraduate was a psychiatrist. He was part of the psych department and taught intro to psych. He taught behavioral neuroscience through the neuro department and he may have taught abnormal psych.
In regards to what whopper said, regardless of who's teaching the course they're an expert in one aspect of the course (the priest, if you will), but know very little about other aspects outside of that. For instance, look at any undergrad course you took; for those that you felt the teacher had expertise on all the subject in the course it's likely because you, as a student, didn't know much about the subject. The more we learn about subjects the more we realize people don't know too much about subjects, which is probably why, as a psychiatrist, he realizes that there would be holes in knowledge when teaching a psych class. The same thing would happen, I beleive, if he were (insert any academic subject) and observed someone teaching that course. Long story short the people who teach courses (any course) have a particular area of expertise one one aspect of that field, like a biochemist, but don't spend their whole career focusing strictly on the direct principles and application of everything within that particular course.
I rambled, but I hope it made sense.