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Lecture 2

NEUROSC 10 Lecture Notes - Lecture 2: Camillo Golgi, Wilhelm His Sr., Gap Junction


Department
Neuroscience
Course Code
NEUROSC 10
Professor
Babiec
Lecture
2

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10/4/17
NEUROSCIENCE 10 LECTURE NOTES
Cellular Organization of the Nervous System
The Neuron
Contains organelles that other cells do
o Cell membranes, nucleus, DNA, etc.
Many specializations for information transfer
o Those specializations are built around its role of information processing and
transmission
o The neuron is highly polarized (has orientation) with dendrites and axon
Very distinctly directional
The cell has distinct geometry, and it doesn’t look all the same
o Dendrites are associated with the reception of information
o Ability to generate axon
o Vesicle release sites for neurotransmitter release
Neurons are postmitotic
o No adult generation of new neurons
Except olfactory bulb and dentate gyrus of hippocampus
o You are born with the set of neurons you’re going to live with the rest of your life
o Early on, you are building and pruning connections
o Many of your axons are unmyelinated when you’re young
Regional stratification of neurons
Many ways to classify neurons
Reticularists (nerve nets) vs. Neuronists
o Neuronists: individual discrete units
o Reticularists: everything is a single continuous network
The neuron:
Has a similar structure to any general cell type in the body within the cell body. Uniquely
features dendrite and axon members; axon is generated as a dendritic growth - one of many
neurites - which develops a growth cone complete with filopodia and lamellopodia, as studied by
Ramon y Cajal, and grows faster and longer than other, similar growths, ultimately becoming the
cells axon, while the other neurites become dendrites instead. Growth and development of axons
may be related to memory enforcement. Most cells have only one axon. The cleft between the
axon of one cell and the dendrite of another is the synaptic cleft. Neurotransmitters kept in
reserve on one side of the cleft may be released as part of an electrochemical reaction during
neuronal activity; they are carried in vesicles across the cleft to the other cell. The polarization of
the cells interior relative to extracellular fluid is key in determining cell behavior during
neuronal firing. Neurons are typically not generated after birth and undergo a massive culling
period during adolescence - this may be related to the solidification of personality and loss of
learning flexibility experienced by individuals in this age range. Myelination similarly continues
throughout roughly the first quarter century of ones life, after which it halts; this too may be a
contributing factor to the above phenomenon.
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