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								-nerve cells 
								-brain contains as many as 100 billion of these  | 
							
							
								 
								Neurons									 
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								Tiny fibers that extend out from the cell body									 
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								Dendrites									 
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								Group of axons bundled together like wires in an electrical cable									 
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								Nerve (tract)									 
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								-white, fatty sheet covering the axon 
								-pinched to make intervals (like sausages)  | 
							
							
								 
								Myelin sheath									 
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								Neurons that collect messages from sense organs and carry those messages to the spinal cord or the brain									 
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								Sensory (afferent) neurons									 
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								Neurons that carry messages from the spinal cord or the brain to muscles and glands									 
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								Motor (efferent) neurons									 
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								Neurons that carry messages from one neuron to another									 
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								Interneurons (association nuerons)									 
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								Specialized neuron cell that mimics the behavior of others									 
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								Mirror neuron									 
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								Hold the nuerons in place, provide nourishment, remove waste products, prevent harmful substances from passing from bloodstream to brain, and form myelin sheath									 
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								Glial cells									 
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								Electrically charged particles									 
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								Ions									 
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								Occurs when there are more negative ions inside the neuron than outside, there is electrical charge									 
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								Polarization									 
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								An electrical charge									 
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								Neural impulse (action potential)									 
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								Small, temporary shift in the electrical charge									 
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								Graded potential									 
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								Every firing of a particular neuron produces an impulse of the same strength									 
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								All or none law									 
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								Tiny gap that separates neurons									 
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								Synaptic space (or cleft)									 
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