12. morphine and codeine are the chief mind-affecting chemicals in the pain-relieving drug a. heroin b. opium c. methadone d. all of the above

In multiple sclerosis, the immune system destroys the substance that coats and protects nerve fibers in the brain and spinal cord. this causes inflammation and injury to the nerves, and the axons don't conduct impulses as well.

Which term defines one's age as measured by how well the body is working? chronological age biological age social age mental age

As you sit in the library with your friend studying for your weekly quiz on the integumentary system, you come upon an article about the hazards of prolonged exposure to the sun's rays. your curious nature leads you to research the subject further. you're fascinated to learn that minimal exposure to the sun allows you skin to manufacture vitamin d, which is important to maintain homeostasis. you also read that although sunscreen can protect you from the ultraviolet (uv) rays of the sun, some medications can actually increase a person's sensitivity to the sunlight.