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Human Biology
Malcolm Mac Kinnon

Chapter 1 The Origins of Neuroscience  Evidence suggests that even our prehistoric ancestors appreciated that the brain was vital to life o There are archeological records with examples of hominid skulls bearing signs of fatal cranial damage o As early as 7000 years ago, people were boring holes in other’s skulls in attempts to cure headaches and disorders as they assumed it was a method to allow evil spirits to depart from the brain  Recovered writings from physicians of Ancient Egypt indicate that they were well aware of many symptoms of brain damage. o However, it was the heart that was considered to be the seat of the soul and the repository of memories.  Views of the Brain in Ancient Greece o Hippocrates (460 – 379 B.C.), the father of western medicine, stated his belief that the brain only was involved in sensation but also was the seat of intelligence. o Not universally accepted. o Aristotle still believed that the heart was the center of intellect and believed the brain was a radiator for cooling the blood that was overheated by the heart.  Views of the Brain During the Roman Empire o Greek physician and writer Galen embraced the Hippocratic view of the brain function o His views were influenced by the many sheep brains he had dissected o Two major parts are evident in a sheep brain: the cerebrum (front) and the cerebellum (back). o He assumed that the soft cerebrum was responsible for memory, receiving sensation and that the cerebellum is responsible for commanding muscle movement o Also saw many ventricles in the brain and assumed the old the theory of four vital fluids (humors) responsible for movements was correct.  Views of the Brain From the Renaissance to the Nineteenth Century o Galen’s view prevailed for nearly 1500 years o The notion that fluid is used to pump the muscles was still prevalent o A chief advocate of this fluid-mechanical theory was Rene Descartes. o However, he also reasoned that unlike animals, humans possess intellect and a God- given soul.  He proposed that the brain mechanisms for a human are similar to that of a beast only to a certain extent.  He believed that the mind is a spiritual entity that receives sensations and commands movements by communicating with the machinery of the brain via the pineal gland. o Scientists began to break away from Galen’s views o On closer observations, the brain was noticed to have gray and white matter  White matter, because it was continuous with the nerves of the body, was correctly believed to contain the fibers that bring information to and from the gray matter. o By the end of the eighteenth century, the nervous system had been completely dissected and scientists realized that it has a central division, consisting of a brain and spinal cord, and a peripheral division with networks of nerves that course through the body. o An important breakthrough was the observation that the same general pattern of bumps (gyri) and grooves (sulci and fissures) could be identified on the surface of the brain in every individual  This pattern enables the parceling of the cerebrum into lobes; the basis of speculation that different functions might be localized to the different bumps on the brain.  Nineteenth Century Views of the Brain o Summary o Injury to the brain can disrupt sensation, movement, and thought and can cause death o The brain communicates with the body via the nerves o The brain has different identifiable parts, which probably performs different functions o The brain operates like a machine and follows the laws of nature o Nerves as Wires  In 1751, Benjamin Franklin published a pamphlet which heralded a new understanding of electrical phenomena  Italian scientist, Luigi Galvani and German biologist Emil du Bois-Reymond had shown that muscles can be caused to twitch when nerves are stimulated electrically and that the brain itself can generate electricity.  This discovery replaced the idea that nerve communication with the brain was controlled by the movement of fluid.  Scottish physician Charles Bell and French physiologist Francois Magendie discovered that by cutting the ventral roots of the nerve fibers caused muscle paralysis and Magendie showed that the dorsal roots carry sensory information into the spinal cord. o Localization of Specific Functions to Different Parts of the Brain  Bell and Magendie employed to identify the functions of the spinal roots: to destroy these parts of the brain and test for sensory and motor deficits  experimental ablation method  Marie-Jean-Pierre Flourens used this method in many animals and showed that the cerebellum does indeed play a role in the coordination of movements. He also concluded that the cerebrum is involved in sensation and perception.  An Austrian medical student, Franz Joseph Gall, believed that the bumps on the skull reflected the bumps on the brain. Flourens thought this was an idiot and he was right.  A French neurologist, Paul Broca, was known for tilting the scales of scientific opinion firmly toward localization of function in the cerebrum.  He was presented with a patient who could understand language but could not speak.  Following that person’s death, Paul examined his brain and found a lesion in the left frontal lobe.  Based on this case and several others, he deduced that region of the human cerebrum was specifically responsible for the production of
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