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22 Topic Pages Found in Health & Medicine and starting with the letter N
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any of a number of substances that have a depressant effect on the nervous system. The chief narcotic drugs are opium , its constituents morphine and

Nasal septum deviation

What Is It? The nasal septum is the wall between the left and right sides of the nose. It is firm, but bendable, and it is covered by skin that has a

Open National Institute on Aging
National Institute on Aging

The National Institute on Aging (NIA), one of the National Institutes of Health (NIH), works to increase understanding of the nature and implications

Open Natural selection
Natural selection

Process by which gene frequencies in a population change through certain individuals producing more descendants than others because they are better


What Is It? Nausea is a general term describing a queasy stomach, with or without the feeling that you are about to vomit. Almost everyone experiences

Open Nervous system
Nervous system

network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the

Neural Tube Defects

Neural tube defects (NTDs) are a collection of congenital disorders related to the failure of neurulation or the process by which the neural tube is


Neurofibromatoses are disorders that affect the skin, nervous system, and bone in children and young adults. The three most common forms are

Open Neurons

Elongated cell that transmits information rapidly between different parts of the body, the basic functional unit of the nervous system . Each nerve


Neuropathy is a neurodegenerative disorder characterized by damage to one or more peripheral nerves. The peripheral nervous system (PNS) transmits