Which of the following is a true statement about the brain barrier system? check all that apply. necessary because brain tissue is irreplaceable, and therefore must be well protected. both brain barriers utilize tight junctions to keep harmful substance from getting to the tissue fluid of the brain. alcohol, caffeine, nicotine, and anesthetics can all cross the brain barrier system. the brain barrier system is susceptible to trauma and damage. the blood-csf barrier blocks csf from leaking into the bloodstream.