PSYB64H3 Lecture Notes - Lecture 3: Bipolar Neuron, Multipolar Neuron, Sensory System
Chapter 3: Neurophysiology: The Structure and Functions of the Cells of the Nervous System
Glia and Neurons!
1. Structure of NS has been shaped through the course of evolution to to carry out functions
for survival and reproduction !
2. 2 Cells make up NS!
I) Glia: Cells in the nervous system that
support the activities of neurons; glue!
II) Neurons: A cell of the nervous system
that is specialized for information
processing and communication!
!
A. Glia!
1. Categorized by size !
I) Macroglia: Largest variety (astrocytes,
oligodendrocytes, and Schwann cells)!
II) Microglia: Smaller variety; mobile glial
cells that migrate to areas of damage and
digest debris!
2. Macroglia!
B. Astrocytes: Support functions to the
neurone !
1. Star like shape & most common!
2. Roles: Provides structural matrix for neurons
+ Transfer nutrients to neurons and block
circulating toxins from blood supply !
3. Neurovascular units: Astrocytes has close connections w/ brain capillaries to transfer
glucose and other nutrients to neurone !
4. Blood brain barrier: Astrocytes help form the BBB by covering outer surface of capillaries w/
end feet !
5. Astrocytes keep neurochemicals from moving outside in synapses OR can clear molecules
in synaptic gap !
6. When CNS neurone are damaged—> astrocytes
form scar tissues which help with overall healing
process but interferes with repairing of damaged
connections !
7. Astroctyes signal neurons to build synapses—>
developed brain and helps with learning and
memory !
8. Releases glutamate and ATP to influence
adjacent neurone and other astrocytes by
exciting or suppressing activity of neurons/
astrocytes !
9. Too much glutamate can kill neurons!
C. Oligodendrocytes & Schwann cells: Supply
myelin covering axon fibres!
1. Oligodendrocytes: Single myelin segment on 15
different neurons—> Structural stability of the
brain and spinal cord (CNS)!
2. Schwann cells: Single myelin segment on one
peripheral axon (PNS) !
Chapter 3: Neurophysiology: The Structure and Functions of the Cells of the Nervous System
3. Injury (schwann)—> Guides regrowth of damaged axons (reattaching limb) vs. oligo which
lacks capacity to do so (brain and spinal cord)!
4. Multiple Sclerosis (MS): Progressive demyelination of the NS (range in symptoms)!
5. Microglia!
I) At rest—> branches reach out and sample environments to clean up any cell debris (ex.
after head injury, stroke) !
II) Uncontrolled activation—> Damage the brain through release of substances—>
inflammation OR digesting healthy cells next to damaged cells !
III) Neurodegenerative disease (alzhemiers, parkinson, MS): Caused by microglia activation !
Connecting to research: Astrocytes, HIV, and BBB!
1. Infected by HIV—> virus goes to CNS—>Leads to HIV-associated neurocognitive disorder!
I) Main target of virus is microglia and astrocytes !
2. Infected astrocytes—> disruption in endfeet and terminals of branches severing the brain
and spinal cord—> Compromised BBB—> More vulnerable to toxins in the brain !
!
D. The structure of neurons !
1. Contain membranes, nuclei, and organelles that are found in cell body or soma !
I) Organelles: A small structure within a cell that carries out a specific function!
II) Cell body/ soma:The main mass of a neuron, containing the nucleus and many
organelles!
2. Neurons differ from other cells in that they have branches extending from the cell bodies,
axons and dendrites !
I) Axons: The branch of a neuron usually responsible for carrying signals to other neurons!
II) Dendrites: The branch of a neuron that generally receives information from other
neurons!
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Chapter 3: Neurophysiology: The Structure and Functions of the Cells of the Nervous System
3. Neural membrane!
I) Role: Separate intraceullar/ cytoplasm
from the extracellular fluid surrounding
the neuron !
II) Chemical composition of fluids are
different and generate neural messages !
III) Composition: double layer of
phospholipids, fatty mol (containing
phosphate), ion channels/ion pumps!
IV) Channels & pumps provide pores for ions
to move in or out of the neuron!
V) Voltage-dependent channels: open and
close in response to the electrical status
of adjacent areas of membrane!
VI) Na-K pumps: Sends 3 Na out while 2 K
go in—> high energy cost (20-40% of
brain) !
VII)Ca pumps: Pumps Ca out of the cell
(important to maintain low levels in
the cell) !
4. Neural cytoskeleton !
I) Cytoskeleton: network of filaments
that provides the internal structure of
a neuron!
II) 3 types of filament that make up the
cytoskeleton !
III) Microtubules: Largest fiber in the cell
cytoskeleton, responsible for the
transport of neurotransmitters and
other products to and from the cell
body!
IV) Anterograde: Away from cell body vs.
retrograde transport: toward cell body !
V) Pathogens (rabies, polio, herpes
simplex, tetanus travel retrograde
(terminal—> cell body) !
VI) Alzheimers: Neurofibrillary tangles
consisting of large amounts of tau
protein—> dissconnections from
microtubules —> tangles hindering cells
ability to signal and maintain structure !
VII)Neurofilaments: neural fiber found in the cell
cytoskeleton that is responsible for structural
support.!
VIII) Microfilament: smallest fiber found in the cell
cytoskeleton that may participate in the
changing of the length and shape of axons
and dendrites (such as in learning/
development) !
Document Summary
Ii) neurons: a cell of the nervous system that is specialized for information processing and communication: glia, categorized by size , macroglia: largest variety (astrocytes, oligodendrocytes, and schwann cells)! Ii) microglia: smaller variety; mobile glial cells that migrate to areas of damage and digest debris: macroglia, astrocytes: support functions to the neurone , star like shape & most common, roles: provides structural matrix for neurons. Ii) uncontrolled activation > damage the brain through release of substances > in ammation or digesting healthy cells next to damaged cells ! Iii) neurodegenerative disease (alzhemiers, parkinson, ms): caused by microglia activation ! Infected by hiv > virus goes to cns >leads to hiv-associated neurocognitive disorder: main target of virus is microglia and astrocytes ! Infected astrocytes > disruption in endfeet and terminals of branches severing the brain and spinal cord > compromised bbb > more vulnerable to toxins in the brain !
