Any substance that produces harmful effects on the human body is called a(n):

Which of the following is NOT a function of the blood–brain barrier?

A) Protects the brain from "foreign invaders." B) Protects the brain from hormones and neurotransmitters in the rest of the body C) Maintains a constant environment, or homeostasis, for the brain. D) Allows water-soluble molecules to pass while defending against fat-soluble molecules.

Upper motor neurons in the corticobulbar tracts control muscles innervated by:

a. Cranial nerves b. Spinal nerves