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Drug abusers experience the following scenario: The pleasure given by their drug (or drugs) of choice is so strong that it is difficult to eradicate even after years of staying away from the substances involved. Certain triggers may cause a drug abuser to relapse. Research shows that long-term drug abuse results in significant changes in brain function that persist long after an individual stops using drugs. It is most important to realize that the same is true of not just illegal substances but alcohol and tobacco as well.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
Looking at the sun may not only cause headache and distort your vision temporarily, but it can also cause permanent eye damage. Any exposure to sunlight adds to the cumulative effects of ultraviolet (UV) radiation on your eyes. UV exposure has been linked to eye disorders such as macular degeneration, solar retinitis, and corneal dystrophies.
Cytomegalovirus affects nearly the same amount of newborns every year as Down syndrome.
![(A) The structure of a neuron, showing the dendrites, nerve cell body, and axon. (B) Photomicrograph](https://biology-forums.com/gallery/47/medium_14755_27_08_12_4_56_11_821215.jpeg)
![(A) The levels of the spinal cord and spinal nerves. (B) Photograph of the spinal cord as it descend](https://biology-forums.com/gallery/47/medium_14755_27_08_12_4_56_12_82161984.jpeg)