3. Cellular Anatomy

• Golgi stain


  Adding silver to a brain to stain some of the cells to see them better. No one knows why or how the cells take up the stain
• Reticular theory


  Theory supported by Golgi that all parts of the nervous system are all part of one, large, interconnected network
• Neuron doctrine


  Idea that the nervous system was a series of interconnected but seperated parts proposed by Santiago Ramon y Cajal
• Neurogenesis


  The creation of new neurons
• Neuron dendrites

  
• Dendrites


  Like the branches of trees, where signals are first detected by the neuron
• Spines


  Tiny protrusions of cell membranes along the dendrites
• Soma (cell body)


  The cell body with all of the organelles in it which eventually processes the signals received through the dendrites, and decides whether or not it should pass them down to the next cell
• Axon


  Primary output extension of the neuron that can branch out
• Nerves


  Bundles of axons
• Axon terminal (axon bouton)


  Small swelling at the end of the axon that is specialized for the release of neurotransmitters used for communication between neurons
• Vesicles


  Packages made out of membrane that bring molecules the neurons use for communication to the terminals
• Myelin sheath


  Tightly wrapped segments of cell membrane around an axon that makes the signals travel much faster and much more reliably
• Synapse


  The physical distance between two neurons
• Cells connected by electrical synapses share cytoplasm but are separated by two different cell membranes
• Adjacent neurons connected by chemical synapses do not share cytoplasm
• Chemical synapses are 15-20 nm across, electrical synapses are 5 nm across
• Multiple sclerosis


  Disease that results in the destruction of myelin. It is not really lethal but causes pain and numbness on the afferent side and muscle spasms on the efferent side. There is no cure, but we know that it's an autoimmune disease where the immune system sees target myelin as an intruder
• Sensory neurons


  Afferent neurons responsible for detecting stimuli. Each one is made for a specific stimuli, so they are a very varied neuron type
• Motor neurons


  Carry signals from the CNS to the rest of the body. The somatic type communicates with skeletal muscles to create voluntary movement. The automatic type release neurotransmitters onto the automatic ganglion outside of the CNS which communicates to smooth muscles to do their thing
• People needed to use the Electron microscope to see synapses because the space they were looking for was smaller than a wavelength of visible light