It can mean my conscious self, or it can mean my brain and body as a unit, or it can mean me as an individual among other individuals, and perhaps that's not all.
I developed from a zygote, was carried to term, and born in the usual way.
The evolved human capacity for speech, which has many aspects. One of them is the instinctive use in adults of particular sounds and ways of speaking and sounding in the presence of even newborns, which as 'motherese' is found in all cultures. Another is the receptivity of children even when small to such human sounds, and to look at the carer's face, and also to look where the carer points, and to have the capacity to associate the carer's sound with the thing pointed at ─ 'car', 'dada', 'cup' &c ─ and more interestingly still, to comprehend these sounds as not just identities but as categories, so that a car never seen before is still recognized as a car. And so on.
Brain mapping began as far back as the 18th century, when it was noted that certain kinds of head injury might have different consequences depending which part of the brain was injured. However, it really took off with the coming of better tools in the 1990s. So our comprehension of the brain, its functions, and the interaction of those function, though still very much a work in progress, has made great advances. We know from real-time brain scans eg that proper nouns are 'stored' in a different part of the brain to other nouns; that one of the functions of the frontal lobes is monitoring / editing speech and conduct, and injury there can cause disinhibition; and so on through a long and growing list.
You only get one life, you get it from your body, and when your body is dead, so are you.
A complex variety of systems, that do a great many things automatically, like control of the water content of the blood and of other cells, response to oxygenation needs, blood sugar balance, and so on. Also automated are your instinctive responses, such as removing your hand instantly from the hot stove, driving your car while you're talking to your passenger, making up these words I'm typing without reference to my conscious brain, and much more. The heart and the gut have their own all but autonomous nervous systems, too.
No, as my previous answer implies, they're a unit. You won't think very well when you're in pain, or ill, or need to breathe, or are intoxicated, or starving, or freezing, or very thirsty, and so on. When the body's happy, the brain is free to do its thing.