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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).
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.
There are 20 feet of blood vessels in each square inch of human skin.
The top 10 most important tips that will help you grow old gracefully include (1) quit smoking, (2) keep your weight down, (3) take supplements, (4) skip a meal each day or fast 1 day per week, (5) get a pet, (6) get medical help for chronic pain, (7) walk regularly, (8) reduce arguments, (9) put live plants in your living space, and (10) do some weight training.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.