Problem:

I'm reading about various parts of the human body and brain and started to wander if there's a branch of biology that deals with the entire human? I know that there are branches various -biologies, from neurobiology to something like heliobiology or chronobiology. All of them look at different organ systems or parts of an organism, but from different points of view.

Then there are sciences that deal with behavior and cognition of humans.
As I read about these, I notice that there's quite a lot of overlap, particularly when neurotransmitters and hormones are involved. For example Melatonin, a hormone has functions in both the brain and the gut.

I'm wondering if there's some form of biology or science that deals with the entire organism, its behavior, as well as its parts.
Am I thinking about Biology or Medicine or something else? Please suggest me something about it.