You ask a good question; "Is 'mind' something apart from the brain or a function of the brain?"
I'd say, straight off, that the mind is a function of the brain. But I would add that how the brain works is just as easily influenced by how the mind works as the other way around. It's possible to alter the chemical balance of the brain by using chemical substances. This will also alter the experience of the mind. But I know for a fact, based on personal experience along with scientific data, that a conscious effort to alter the experience of the mind can change the chemical balance of the brain. The two are linked; they are two sides of the same coin.
But more to the point, I am a very spiritually inclined person. The people who know me come to me when they need guidance in issues concerning non tangible forces that influence us. When they do not have the foundation or the conceptual basis to navigate by themselves. I am able to provide support, and by asking the ocasional question, to highlight certain aspects that are worthy of further contemplation.
We each create our own metaphysical reality in which we live, an image of the world in which we function. This is a spiritual thing. Every human being does this, wether he knows it or not. Among my friends there are those who pay this process no attention at all. They see it as not worthy of their time. But they have also seen me maintaining my strength in the face of things that would bring them to their knees. So when they face difficulties they cannot handle they turn to me for guidance. Not because I possess skills they don't have. Simply because I have chosen to explore the realm of the unseen, the functions that enable us to act as human beings.
In a way, as I see it, a person does what humans do by virtue of being what they are. You can do this without paying attention to the process itself.
To pay attention to the process is to be aware of the spiritual aspect of existence.
To put it a bit more bluntly; I never bring this imagery up unless I want to provoke someone for any given reason:
If you simpy exist within the bounds set for you, if you just react to what happens to you without questioning how things affect you, how can you set yourself apart from sheep, or monkeys or ants or any other living organism? To be aware of the functions behind your own existence is the very ability that sets us apart from all other living creatures on this planet. These functions are our spirituality. If you pay them no heed you are a puppet to your wants and needs. To live in such a way is to live like an animal. Do it if you wish, I know that I have the potential to extract a lot more from existence that that, simply by embracing my spirituality.