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Psychology 304:
Brain and Behaviour
Lecture 10
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The Cells of the Nervous System
1. What is the structure of the neuron?
2. What are glial cells?
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By the end of today’s class, you should be able to:
1. describe the external structural features of the neuron.
2. describe the internal structural features of the neuron.
3. distinguish between unipolar, bipolar, and multipolar
neurons.
4. identify the types and functions of glial cells.
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What is the structure of the neuron?
• The external structure of the neuron is characterized by
eight features:
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Cell body: The metabolic center of the neuron. Also
called the soma.
Cell membrane: A semipermeable membrane that encloses
the neuron.
Axon: A long, narrow extension that projects from the cell
body.
Axon hillock: The cone-shaped region at the junction
between the axon and cell body.
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Myelin sheath: Fatty insulation surrounding the axon.
Nodes of Ranvier: Gaps between sections of myelin.
Dendrite: A short extension emanating from the cell body
that receives contacts from other neurons.
Terminal buttons (axon terminals): Button-like endings
on axon branches that contain chemicals for
communication between cells (i.e., neurotransmitters).
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Dendrite
Terminal button
Cell body
Axon
Cell membrane
Nodes of
Ranvier
Myelin sheath
Axon hillock
External Features of a Typical Neuron
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Image of a Neuron Produced by
Light Microscopy
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• The internal structure of the neuron is characterized by
nine features:
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Nucleus: The spherical DNA-containing structure of the
cell body.
Cytoplasm: The clear internal fluid of a cell.
Mitochondria: Sites of energy production and release.
Endoplasmic reticulum: A system of folded membranes;
Rough portions are involved in protein synthesis. Smooth
portions are involved in fat synthesis.
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Ribosomes: Located on rough endoplasmic reticulum.
Cellular structures on which proteins are synthesized.
Golgi complex: A system of membranes that packages
molecules in vesicles.
Microtubules: Tubules that allow for the rapid transport
of material throughout neurons.
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Golgi complex
Endoplasmic
reticulum
Ribosomes
Internal Features of the Cell Body
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Photomicrograph of a Neuron Cell Body
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Synaptic vesicles: Spherical membrane packages that
store neurotransmitter molecules ready for release from
the terminal button.
Neurotransmitters: Molecules that are released from
the terminal buttons of active neurons and influence the
activity of other cells.
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Terminal button
Microtubule
Mitochondrion
Synaptic vesicles
Neurotransmitters
Internal Features of the Terminal Button
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Synaptic contact
Mitochondria
Synaptic vesicles
Images of Synaptic Vesicles
Produced by Electron Micrography
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• There are three primary classes of neurons:
1. Unipolar (monopolar) neurons: Have one projection
extending from the cell body.
2. Bipolar neurons: Have two projections extending from
the cell body.
3. Mutlipolar neurons: Have more than two projections
extending from the cell body (e.g., one axon and
many dendrites). The most common type of neuron
found in the CNS.
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Dendrites
Axon
1. Bipolar neuron
2. Multipolar neuron
3. Unipolar neuron
Classes of Neurons
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• Neurons vary substantially in size and complexity.
In contrast to small neurons, large neurons detect and
transmit more information and cover greater distances.
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Variability in the Size and Complexity of Neurons
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What are glial cells?
• Found throughout the nervous system; more common
than neurons.
• Surround and support neurons, control the supply of
nutrients to neurons, assisting in the exchange of
chemicals between neurons, destroy and remove
neurons damaged by disease or injury.
• Four types of glial cells have been identified:
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1. Oligodendrocytes: Produce the myelin sheaths that
surround the axons of neurons of the CNS.
Extensions from a single oligodendrocyte wrap
around the axons of multiple neurons.
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Myelination of Axons in the CNS by
Oligodendrocytes
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2. Schwann cells: Produce the myelin sheaths that
surround the axons of neurons of the PNS.
Multiple
Schwann cells wrap around the axon of a
.
single neuron.
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Myelination of Axons in the CNS by
Oligodendrocytes vs. Myelination of Axons in the
PNS by Schwann Cells
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3. Microglia: The smallest glial cells. Trigger
inflammatory responses to brain damage and remove
injured or dead neurons.
4. Astrocytes: The largest glial cells. Hold neurons in
place, provide nutrients (e.g., lactate) to neurons,
limit the “dispersion” of neurotransmitters released
by terminal buttons, and remove injured or dead
neurons.
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Microglia
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Microglia
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Structure of Astrocytes
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Microglia
Astrocytes
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The Cells of the Nervous System
1. What is the structure of the neuron?
2. What are glial cells?
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