Notes for "The Marriage Tree"
Even the words used to describe the human brain are botanical: limbus referring to the limbic system, where all emotion occurs is a word whose ancient meaning was "limb of a tree." Cortex, that deep part of the brain where language and abstract thought happen, means "bark."
I am told of the delicate nature of the tree's parts: of cambium, the inner layer of cells between phloem and xylem, and how remarkably sensitive it is to any strain on the tree. And the way bark acts as a waterproof covering to the thin layer of living tissue within. A tree's breathing is slow and slight. The respiratory pores in the bark, called lenticels, must have ample space. As the tree ages, the central heartwood thickens and the girth of the trunk widens to accommodate decay.
3. the physiology of memory Thoughts arise as electrical impulses; bits of thought and sensation are neural plasma shuttling from cell to cell, spreading like a net. There's a rhythmical pattern of firing activity, and wild chemical reactions occur: calcium is released and in turn activates an enzyme called calpain, which scrubs connective tissue between neurons "the rootlike dendrites" cutting into the cytoskeleton and, in this way, exposing receptors. Through these, information is absorbed; memory is etched in, and the dendritic brainscape, a place that looks like the cracks in ice on my lake, changes its shape forever.
From "Island, The Universe, Home," by Gretel Ehrlich
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