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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.
Side effects from substance abuse include nausea, dehydration, reduced productivitiy, and dependence. Though these effects usually worsen over time, the constant need for the substance often overcomes rational thinking.
Vaccines prevent between 2.5 and 4 million deaths every year.
The most common childhood diseases include croup, chickenpox, ear infections, flu, pneumonia, ringworm, respiratory syncytial virus, scabies, head lice, and asthma.
Elderly adults are living longer, and causes of death are shifting. At the same time, autopsy rates are at or near their lowest in history.