A scan shows that a particular substance has spread throughout the body via the bloodstream but has not entered the brain. This finding demonstrates the existence of
A) the blood-brain barrier.
B) blood efficacy.
C) medicine effects.
D) the lipid bilayer.
E) the doctrine of specific nerve energies.

Question

Quizplus · Accepted Answer

The fact that the substance has spread throughout the body via the bloodstream but has not entered the brain indicates that there is a barrier that prevents substances from crossing from the blood into the brain. This barrier is known as the blood-brain barrier and is composed of specialized cells that tightly regulate what substances can enter the brain.

A Scan Shows That a Particular Substance Has Spread Throughout