The Root of Thought Read Online Free PDF Page B

cortex—an area dominated by glia?
    The assumption from electrical and cellular studies presented until the twentienth century was that the neural cell body was responsible for everything. Its axon was shown to extend from the brain to the body. And now that it was known to be electrical, all the thoughts in our brain were believed to stem from this electrical pulse in the peripheral nerves demonstrated by Galvani.
    In the twentieth century, by placing neurons in a vacuum tube with sensitive electrodes with such small points they could stab into a small bundle of axons, scientists were able to accurately judge the electrical conductance in an axon. Britain’s Charles Scott Sherrington (1857–1952) developed ways to scientifically study reflexes. He coined the understanding of the synapse as the interstitial space between neurons the year Golgi and Cajal received the Nobel Prize and would win the Nobel Prize himself in 1932. The incremental notion of separate cellular structure by Sherrington and Cajal eliminated Golgi’s concept of the syncytium.
    At the end of an axon, the synapse is the breach between communicating to the next neuron. The first molecule discovered to transmit across the synapse was acetylcholine at the muscles (the chemical compound that activates muscles and is a major neurotransmitter in the autonomic nervous system). Subsequently, nicotine was known to mimic acetylcholine. Scientists looking at the action of drugs discovered many of the other currently known transmitters. Cocaine led to the discovery of dopamine, morphine/heroin led to the discovery of serotonin, marijuana led to the discovery of cannabinoids, and nitrous oxide led to the discovery of nitrous oxide. These molecules are important transmitters between cells.
    The eventual accurate “in-depth” reporting inside an axon was accomplished with a giant squid axon. British scientists Alan Hodgkin (1914–1998) and Andrew Huxley (1917–) and half brother of famous writer Aldous Huxley) inserted an electrode through a single axon and determined the resting potential as –60 or –70 millivolts in 1939. In 1908, Walther Nernst (1864–1941) published an equation that predicted electrical potential based on electrolyte distribution. When measuringextracellular and intracellular space, nerves would have –85 to –90 based on the equation. This was eventually reported by Australian scientist John Eccles (1903–1997) in the 1960s. All of these men would win the Nobel Prize.
    How a Neuron Transmits
     
    When the nerve is stimulated, sodium ions enter inside the cell through exclusive channels that are opened only when firing is primed by an active cell upstream. The resting electrical potential of the neuron is –70 millivolts. When enough sodium enters the cell and the electrical potential changes enough that it crosses a threshold, it shoots to +50 millivolts as the floodgates open and sodium rushes in causing potassium to rush out. Afterwards, a resulting undershoot below resting potential occurs. During this “refractory period,” the neuron is unable to fire until it returns back to the normal resting potential of –70 again.
     
    But all of this groundwork was been done in long peripheral axons extending to the body. It has been done on simplistic relexes. Not at the cellular level in the brain. The studies have revealed a lot about the neuron, but have only been able to infer how we think on a cellular level.
    It is commonly believed that neurons transmit to each other constantly and that our senses solidify some connections while reducing the influence of others. They either fire or don’t. This “all-or-nothing” firing is believed by some to control thought through a binary code. This constant firing is how our thoughts happen. However, the seat of imagination and the provocateurs of neural action would be best served in a different type of cell, a cell that controls the reflexive action of axonal conductance. This cell is not