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Author Question: Before the nation's first transcontinental railroad was completed, travelers to the Pacific Coast ... (Read 76 times) |
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
There are major differences in the metabolism of morphine and the illegal drug heroin. Morphine mostly produces its CNS effects through m-receptors, and at k- and d-receptors. Heroin has a slight affinity for opiate receptors. Most of its actions are due to metabolism to active metabolites (6-acetylmorphine, morphine, and morphine-6-glucuronide).
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Every 10 seconds, a person in the United States goes to the emergency room complaining of head pain. About 1.2 million visits are for acute migraine attacks.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.