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NPB 12, Lecture 2 - LECTURE 2: The broad view of the...

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LECTURE 2:The broad view of the nervous systemWhat, exactly, is the nervous system made out of?From the times of the earliestmicroscopes it was recognized that all organs in the human body, including the brain, arecomposed of individual units, called cells.In the brain there are two types of cells:neurons and glia.The neurons are the ones that actually communicate with each other,by electrical and chemical means, and are responsible for movement, perception, thought,personality, etc.The original view was that the glia are support cells that regulate theenvironment and give the neurons a substrate, or scaffolding, in which to live in.Turnsout that the more we learn about these cells the more we are beginning to understand thatit is not at all that simple.But since this is an introductory neuroscience course, we’ll justsay that is the case as far as exams and stuff goes, but don’t be surprised if you heardifferently in the not too distant future.Now, if you are an 1800s neuroanatomist, these cells look different than what you areused to seeing if you look at muscle cells, or heart cells, or liver cells, etc.All of themseem to have a kind of balloon somewhere, with many little branches going in alldirections around it.Another thing that you will notice is that most of these branchesstart out pretty big near the balloon, and get narrower as you go out.But one startsskinny and stays skinny, and always seems to go a long distance.When a scientist is confronted with something that at first glance appears to be novel,there are two courses of action that can be taken: Either figure out what it is like, or findout how it is different.First we'll go through the similarities between neurons and othercells, which is at the balloon part, and then the specializations.All neurons have a cell body, which is also called a soma, or a perikaryon.This is thepart that shares the most similarities with other cells of the body.The cell body is wherethe proteins and other important parts are made.It is only here that the genes are madeinto proteins, and this is the most important part of the neuron, because if it dies, theentire cell dies.Cell Membrane (Plasma membrane): This surrounds the cell and maintains the integrityof the cell.It is a lipid bilayer, with a hydrophilic region at one end, and twin tails ofhydrophobic regions as the other.The hydrophobic regions align themselves together,making a sort of sandwich.Floating along in the sea of membrane are proteins, such aschannels and receptors, and ion pumps, all of which we will go into more detail later.Nucleus:This is where the DNA / genes resides, and where the RNA is made.These are things that all mammalian cells share.There are several things about neuronsthat make them quite different from most other cells of the body:1) Neurons do not reproduce throughout life.Many types of cells, for example skin andhair, will continue to divide and multiply throughout life.

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Term
Fall
Professor
PAPPONE
Tags
cells

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