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. the doctrine of specific nerve energies.
c. blood efficacy.
d. medicine effects.
Question 2
Experiencing hunger or seeing color in the environment are possible via the:
a. sensory neurons.
b. interneurons.
c. motor neurons.
d. glial cells.