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  • In the late 1860s, scientists believed they were on the verge

  • of uncovering the brain's biggest secret.

  • They already knew the brain controlled the body through electrical impulses.

  • The question was, how did these signals travel through the body

  • without changing or degrading?

  • It seemed that perfectly transmitting these impulses

  • would require them to travel uninterrupted along some kind of tissue.

  • This idea, called reticular theory,

  • imagined the nervous system as a massive web of tissue

  • that physically connected every nerve cell in the body.

  • Reticular theory captivated the field with its elegant simplicity.

  • But soon, a young artist would cut through this conjecture,

  • and sketch a bold new vision of how our brains work.

  • 60 years before reticular theory was born,

  • developments in microscope technology

  • revealed cells to be the building blocks of organic tissue.

  • This finding was revolutionary,

  • but early microscopes struggled to provide additional details.

  • The technology was especially challenging for researchers studying the brain.

  • Soft nervous tissue was delicate and difficult to work with.

  • And even when researchers were able to get it under the microscope,

  • the tissue was so densely packed it was impossible to see much.

  • To improve their view,

  • scientists began experimenting with special staining techniques

  • designed to provide clarity through contrast.

  • The most effective came courtesy of Camillo Golgi in 1873.

  • First, Golgi hardened the brain tissue with potassium bichromate

  • to prevent cells from deforming during handling.

  • Then he doused the tissue in silver nitrate,

  • which visibly accumulated in nerve cells.

  • Known as theblack reaction,”

  • Golgi's Method finally allowed researchers to see the entire cell body

  • of what would later be named the neuron.

  • The stain even highlighted the fibrous branches

  • that shot off from the cell in different directions.

  • Images of these branches became hazy at the ends,

  • making it difficult to determine exactly how they fit into the larger network.

  • But Golgi concluded that these branches connected,

  • forming a web of tissue comprising the entire nervous system.

  • 14 years later, a young scientist and aspiring artist

  • named Santiago Ramón y Cajal began to build on Golgi's work.

  • While writing a book about microscopic imaging,

  • he came across a picture of a cell treated with Golgi's stain.

  • Cajal was in awe of its exquisite detailboth as a scientist and an artist.

  • He soon set out to improve Golgi's stain even further

  • and create more detailed references for his artwork.

  • By staining the tissue twice in a specific time frame,

  • Cajal found he could stain a greater number of neurons with better resolution.

  • And what these new slides revealed would upend reticular theory

  • the branches reaching out from each nerve cell

  • were not physically connected to any other tissue.

  • So how were these individual cells transmitting electrical signals?

  • By studying and sketching them countless times,

  • Cajal developed a bold, new hypothesis.

  • Instead of electrical signals traveling uninterrupted across a network of fibers,

  • he proposed that signals were somehow jumping from cell to cell

  • in a linear chain of activation.

  • The idea that electrical signals could travel this way was completely unheard of

  • when Cajal proposed it in 1889.

  • However his massive collection of drawings supported his hypothesis from every angle.

  • And in the mid-1900s, electron microscopy further supported this idea

  • by revealing a membrane around each nerve cell

  • keeping it separate from its neighbors.

  • This formed the basis of theneuron doctrine,”

  • which proposed the brain's tissue was made up of many discrete cells,

  • instead of one connected tissue.

  • The neuron doctrine laid the foundation for modern neuroscience,

  • and allowed later researchers to discover that electrical impulses

  • are constantly converted between chemical and electrical signals

  • as they travel from neuron to neuron.

  • Both Golgi and Cajal received the Nobel Prize

  • for their separate, but shared discoveries,

  • and researchers still apply their theories and methods today.

  • In this way, their legacies remain connected as discrete elements

  • in a vast network of knowledge.

In the late 1860s, scientists believed they were on the verge

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B1 TED-Ed tissue electrical neuron stain connected

The artist who won a Nobel Prize... in medicine - Melanie E. Peffer

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    林宜悉 posted on 2021/02/08
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