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special chemical molecules that transmit nerve impulses across a synapse.
highly addictive substance found in tobacco that accelerates the heart rate, and contracts and...
pollutant gases such as nitrogen monoxide and nitrogen dioxide. They are produced during ...
bacteria that convert nitrogen in the air into compounds such as nitrites, nitrates and ammonia...
animal wastes (particularly urine) that contain materials high in nitrogen.
gaps (about 1 micrometre long) that occur between the myelin sheaths generated by consecutive...