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These Toxins Are Threatening Our Brains

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How toxins destroy brain cells:

About a quarter of your body’s metabolism goes toward operating and maintaining your brain. In order to process even basic information, billions of chemical signals are constantly being carried between neurons. The undertaking is so onerous that even though your brain is not moving (like, say, the powerful muscles in your legs), it uses around 10 times more calories per pound than the rest of you.

Most of that industrious brain and its 86 billion neurons were created in a matter of months. During the first few weeks of gestation, when your mother knew you only as morning sickness and you were a layer of cells huddled in one corner of her uterus, those cells lined up, formed a groove, and then closed to form a tube. One end of that tube eventually became your tiny spinal cord. The rest expanded to form the beginnings of your brain.

For a brain to develop properly, neurons must move to precise places in a precise sequence. They do so under the direction of hormones and chemical neurotransmitters like acetylcholine. The process is an intricate, fast-paced dance on a very tiny scale. Each nerve cell is about one hundredth of a millimeter wide, so it has to travel its own width 25,000 times just to move an inch—which some neurons in the cortex must. At any point, that cell can be knocked off course. Some of the neurotoxins Grandjean and Landrigan discuss have the potential to disrupt this journey, in a slight or serious fashion.

By the third trimester, the surface of the brain begins folding itself into wrinkled peaks and valleys, the gyri and sulci that make a brain look like a brain. Specific areas of that cortex learn to process specific aspects of sensation, movement, and thought, and that starts in the uterus. As Grandjean explains this process in his 2013 book Only One Chance, “Usage promotes function and structure, as the connectivity of the brain cells is shaped by responses to environmental stimuli.” That is, the fetal brain starts having experiences that form the basis for learning and memory. The nature-nurture duality begins at conception.

By age two, almost all of the billions of brain cells that you will ever have are in their places. Except in the hippocampus and one or two other tiny regions, the brain does not grow new brain cells throughout your life. When brain cells die, they are gone. So its initial months of formation, when the brain is most vulnerable, are critical. “During these sensitive life stages,” Grandjean and Landrigan write, exposure “can cause permanent brain injury at low levels that would have little or no adverse effect in an adult.”

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