Should be a chemical reaction
The solid food is breaking down and turning into a different type of substance, so it should be a chemical reaction. Please tell me if I am right.
answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.