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Unformatted text preview: Neural Communication CELLS IN THE BRAIN It wasn't until Ramon y Cajal (Spanish anatomist) at the end of the 19th century that it was proposed that the brain is composed of separate cells, with separate functions, metabolism, structure). Not until around 1950 -- when the electron microscope was invented -- that this was actually confirmed. (Talk about being ahead of your time!) The pictures below are from the lecture and show the intricate structure of the neurons and their network. The picture on the left shows neurons that have been stained with a fluorescent marker. The picture on the right shows a neuron stained using the Golgi stain, which was developed by Camillo Golgi (who shared the Nobel prize with Cajal) over a 100 years ago. It is still in use today! Drawings of neurons made by Cajal based on a microscopic view of human cortical tissue stained using the Golgi stain . Pyramidal Cells in the Hippocampus So, you might askwhy should a psychologist like me learn about the details of electrical and chemical communication within and between neurons? Here are examples of the reasons why this is necessary. Ever heard of EEG's ? Read pp 87-88! Electroencepholograms are measurements of the electrical conductance in neurons that can be measured on the surface of the skull, that is the EEG sums up lots of resting potentials and action potentials and in this fashion gives a sense of how much activity is going on within regions of the cerebral cortex.. Read Epilepsy is sometimes described as an uncontrolled electrical storm in the brain. Epilepsy occurs when neurons fire action potentials uncontrollably, presumably their threshold for firing is lowered. Read BOX 3.2! Here are the basic steps in how information is conducted in the central and peripheral nervous system 1. Resting Potential At rest the axon has an electrical charge of approximately 70 millivolts (it varies in different axons from 60 to 80 mV) 2. Action Potential If depolarized (made more positive) then the axon may reach threshold (about 10-20 mV more positive). If threshold is reached (about 50mV) an action potential is fired. It travels in an all or none fashion, never losing strength, down the entire length of the axon. 3. Graded Potential The dendrites conduct information by decremental conductance (cable properties)....
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- Spring '08