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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).
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
There are more nerve cells in one human brain than there are stars in the Milky Way.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.