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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.
During pregnancy, a woman is more likely to experience bleeding gums and nosebleeds caused by hormonal changes that increase blood flow to the mouth and nose.
Of the estimated 2 million heroin users in the United States, 600,000–800,000 are considered hardcore addicts. Heroin addiction is considered to be one of the hardest addictions to recover from.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.
Medications that are definitely not safe to take when breastfeeding include radioactive drugs, antimetabolites, some cancer (chemotherapy) agents, bromocriptine, ergotamine, methotrexate, and cyclosporine.
![Female individuals of the banded Uromastyx, Uromastyx flavofasciata, are different colours. Most nat](https://biology-forums.com/gallery/47/medium_33_22_09_11_9_37_27_18101556.jpeg)
![Competition can be (a) direct, or (b) indirect interaction among individuals of the same or differen](https://biology-forums.com/gallery/47/medium_33_17_02_12_5_28_58_19442225.jpeg)