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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).
Approximately 70% of expectant mothers report experiencing some symptoms of morning sickness during the first trimester of pregnancy.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
![Position of the lungs within the thoracic cavity; anterior view illustrating regions of the lungs an](https://biology-forums.com/gallery/47/medium_14755_10_09_12_7_13_31_84901393.jpeg)
![The medical assistant holds the position of the thermometer while the temperature is being obtained.](https://biology-forums.com/gallery/47/medium_665046_06_03_17_1_45_26_262972351.jpeg)