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Lecture

Chapter_2a.docx

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Department
Psychology
Course Code
PSYC 371
Professor
Sidney Eve Matrix

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Chapter 2: Neuron and Glia
Neurons and Glia are cells in the nervous system and are broad categories, within which are
many types of cells that differ based on their structure, chemistry and function
Glia outnumber neurons by tenfold
Neurons are the most important cells for the unique functions of the brain.
o They sense the changes in the environment, communicate these changes to other
neurons, and command the body’s responses to these sensations.
Glia (glial cells) are thought to contribute to brain function mainly by insulating, supporting, and
nourishing neighboring neurons
The Neuron Doctrine
The Golgi Stain
o The Golgi Stain shows that neurons have at least two distinguishable parts: a central
region that contains the cell nucleus and numerous this tubes that radiate away from
the central region
o The swollen region containing the nucleus has several names that are used
interchangeably; most notably the cell body and soma
o The thing tubes that radiate away from the soma are called neuritis and are of two
types: axons and dendrites
o The cell body usually gives rise to a single axon.
The axon is of uniform diameter throughout its length, and if it branches, the
branches generally extend at right angles
Axons can travel long distances (a meter or more); dendrites, however, rarely
extend more than 2 mm in length.
Cajal’s Contribution
o Argued that the neuritis of different neurons are not continuous with one another and
must communicate by contact, not continuity
o This became known as the neuron doctrine and the brother won a Nobel Prize
The Prototypical Neuron
The Soma
o Roughly spherical central part of the neuron
o Is about 20 µm in diameter
o Watery fluid inside the cell (cytosol) is salty, potassium rich and separated from the
outside
o The cell body of the neuron contains the same organelles that are found in all animal
cells
The most important:
Nucleus
The rough ER
The smooth ER
The Golgi apparatus
Mitochondria
o Everything within the cell membrane, excluding the nucleus is collectively known as the
cytoplasm
o The Nucleus
Spherical, centrally located and is contained within a double membrane called
nuclear envelope
Contains chromosomes and DNA
o The Rough Endoplasmic Reticulum
Not far from the nucleus
Enclosed stacks of membrane dotted with ribosomes
Contains an abudance of neurons
Major site of protein synthesis in neurons
Some are produced on free ribosomes
So what’s the difference?
If the protein is destined to reside within the cytosol of the
neuron, then the protein’s mRNA moves towards the free
ribosome
If the protein is destined to be inserted in a membrane or an
organelle, then it is synthesized in the rough ER.
o Smooth ER and the Golgi Apparatus
Is actually quite heterogeneous and performs different functions in different
locations
Some types of smooth ER play no direct role in the processing of protein
molecules but instead regulate the internal concentrations of
substances
The Golgi apparatus is believed to be the sorting of certain proteins that are
destined for delivery to different parts of the neuron (e.g. axon and dendrites)
o The Mitochondrion
Very abundant in the soma
Site of cellular respiration and uses ATP as energy currency
o The Neuronal Membrane
Serves as a barrier to enclose the cytoplasm inside the neuron and to exclude
certain substances between both sides of the barrier
o The Cytoskeleton
Gives the neuron its characteristic shape
The bones that make up the cytoskeleton are the microtubules, microfilaments,
and neurofilaments
Microtubules
Big and run longitudinally down neuritis
Appears as a straight, thick-walled hollow pipe
Microfilaments
About the same thickness as a cell membrane
Found throughout the neuron and are particularly numerous in
the cell membrane
Neurofilaments
Are intermediate in size
Only neurons they are called neurofilaments but exist in all cells

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Description
Chapter 2: Neuron and Glia  Neurons and Glia are cells in the nervous system and are broad categories, within which are many types of cells that differ based on their structure, chemistry and function  Glia outnumber neurons by tenfold  Neurons are the most important cells for the unique functions of the brain. o They sense the changes in the environment, communicate these changes to other neurons, and command the body’s responses to these sensations.  Glia (glial cells) are thought to contribute to brain function mainly by insulating, supporting, and nourishing neighboring neurons The Neuron Doctrine  The Golgi Stain o The Golgi Stain shows that neurons have at least two distinguishable parts: a central region that contains the cell nucleus and numerous this tubes that radiate away from the central region o The swollen region containing the nucleus has several names that are used interchangeably; most notably the cell body and soma o The thing tubes that radiate away from the soma are called neuritis and are of two types: axons and dendrites o The cell body usually gives rise to a single axon.  The axon is of uniform diameter throughout its length, and if it branches, the branches generally extend at right angles  Axons can travel long distances (a meter or more); dendrites, however, rarely extend more than 2 mm in length.  Cajal’s Contribution o Argued that the neuritis of different neurons are not continuous with one another and must communicate by contact, not continuity o This became known as the neuron doctrine and the brother won a Nobel Prize The Prototypical Neuron  The Soma o Roughly spherical central part of the neuron o Is about 20 µm in diameter o Watery fluid inside the cell (cytosol) is salty, potassium rich and separated from the outside o The cell body of the neuron contains the same organelles that are found in all animal cells  The most important:  Nucleus  The rough ER  The smooth ER  The Golgi apparatus  Mitochondria o Everything within the cell membrane, excluding the nucleus is collectively known as the cytoplasm o The Nucleus  Spherical, centrally located and is contained within a double membrane called nuclear envelope  Contains chromosomes and DNA o The Rough Endoplasmic Reticulum  Not far from the nucleus  Enclosed stacks of membrane dotted with ribosomes  Contains an abudance of neurons  Major site of protein synthesis in neurons  Some are produced on free ribosomes  So what’s the difference?  If the protein is destined to reside within the cytosol of the neuron, then the protein’s mRNA moves towards the free ribosome  If the protein is destined to be inserted in a membrane or an organelle, then it is synthesized in the rough ER. o Smooth ER and the Golgi Apparatus  Is actually quite heterogeneous and performs different functions in different locations  Some types of smooth ER play no direct role in the processing of protein molecules but instead regulate the internal concentrations of substances  The Golgi apparatus is believed to be the sorting of certain proteins that are destined for delivery to different parts of the neuron (e.g. axon and dendrites) o The Mitochondrion  Very abundant in the soma  Site of cellular respiration and uses ATP as energy currency o The Neuronal Membrane  Serves as a barrier to enclose the cytoplasm inside the neuron and to exclude certain substances between both sides of the barrier o The Cytoskeleton  Gives the neuron its characteristic shape  The bones that make up the cytoskeleton are the microtubules, microfilaments, and neurofilaments  Microtubules  Big and run longitudinally down neuritis  Appears as a straight, thick-walled hollow pipe  Microfilaments  About the same thickness as a cell membrane  Found throughout the neuron and are particularly numerous in the cell membrane  Neurofilaments  Are intermediate in size  Only neurons they are called neurofilaments but exist in all cells  The Axon o Found only in neurons and is highly specialized for the transfer of information over distances in the nervous system o It begins with a region called the axon hillock o Two features distinguish the axon from the soma:  No rough ER extends into the axon, and there are few, if any, free ribosomes  The protein composition of the axon membrane is fundamentally different from that of the soma membrane o Since there are no ribosomes, no protein synthesis can occur in the axon and thus, all proteins present must originate in the soma.  The different proteins in the axonal membrane allow it to serve as a telegraph wire and send information over great distances o Axons often branch and these branches are called axon collaterals  Those branches that return to communicate with the same cell that gave rise to the axon or with the neighbouring cells are called recurrent collaterals. o The diameter of an axon is variable and this variation is important  The thicker the axon, the faster the information is sent and the thinner the axon, the slower the information is sent  The Axon Terminal o All axons have a beginning (the axon hillock), a middle (axon proper) and an end called the axon terminal or terminal bouton o It is the site where the axon comes in contact with other neurons and passes info onto them o This point of contact is referred to as the synapse o Sometimes axons have many branches at their ends and e
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