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Lecture 3

PSY290H5 Lecture Notes - Lecture 3: Pyramidal Cell, Multipolar Neuron, Grey Matter

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Alison Fleming

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Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Neurons are Classified into Three Principle Types
- They all have some kind of input zone (receive information
from surrounding cells), an integration zone (a number of
inputs that are connecting up and combining information up
together to one point), a conduction zone that transfers
information from one neuron to another, and then another
input zone to connect the pathway down
- About 70-75% of all neurons are characterized by the
pyramidal neuron style
a multipolar neuron because it only has one axon
(output zone) and many dendrites (input zone)
- bipolar neurons have one axon and one dendrite (you have
the cell body in the middle with fewer branches off of a
dendrite extending from the cell body)
- unipolar neurons are characterized by a single extension
from a cell body, branching off into one axon and dendrite that stem from the single extension
- there are about 100 different types of neurons in the central nervous system that can be characterized by what
they do
- motor neurons carry information, usually across large distances to muscles and glands (efferent)
- sensory neurons bring information from stimuli to the brain (afferent)
- interneurons connect afferent and efferent circuits together
Golgi-Stained Pyramidal and Stellate Neurons
- pyramidal neurons are usually excitatory neurons
- stellate neurons are the main type of inhibitory neurons (suppressing signals) shape and sculpt connections (the
“brakes” on neuronal activity)
Size of Some Neural Structures and the Units of Measures
- all cells are encapsulated in a section ½ thick; everything below this
section are all of the connection pathways to the brain (white
because it contains myelin) where the communication highway is
- it’s in the gray matter that all of the cell bodies exist
Sizes of Some Neurons
- some neurons in invertebrate organisms are so large that you can
see it with the human eye (they’re so myelinated)
- synapse is about 50 nm wide
- because these things are much smaller than light, they can’t be
visualized with light microscopes (you need electron microscopes
which can resolve images to about 1 nm in size)
Layers of the Cerebral Cortex
- there are 6 main layers described with cellular and functional
distinctions between them
1. closest to the surface of the cortex (outermost layer)

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2. serves for lateral communication within an area, often inhibitory in nature
3. serves for lateral communication within an area, often inhibitory in nature
4. main input layer, excitatory input (connections that are coming from sensory receptors and other pathways
of the brain)
5. main output layer, excitatory input
6. main output layer, excitatory input; closer to the inside of the brain
The Neural Cell Body
- every neuron has to have a cell body
- an area that can integrate neural information and
maintain the functional properties of neurons
- contains a number of different structures:
DNA (genetic information)
nucleus (manufacturing of proteins)
rough and smooth endoplasmic reticulum
(production and manufacturing of proteins)
Golgi apparatus (proteins)
mitochondria (energy production)
Axons and Dendrites
- Dendrites
are the main input area (do the main bulk of information receiving)
multiple branches (spines)
dendrites are doing the structural changes associated
with learning (the number of spines changes with
learning not necessarily changing the number of
- Axons
Main output zone
Carry signals from one neuron to another via action
Conduction of action potentials
Can be very short in nature (only a few nanometers),
but can also be as long as something connecting from your brain to the bottom of your foot (a couple of
Transport of information needs to be supported by something: myelination
Gaps in axons are known as nodes of Ranvier (usually spaces about 20 to 200 microns apart from each
Glial Cells Support Axon Functions
- Glial cells assist neuronal activity by providing raw materials, chemical signals, and structure
- Glial cells serve a variety of functions within the brain
Don’t carry action potentials
Provide nutrients
Remove unwanted neurons (waste)
Form some measure of myelination
- Myelination via oligodendrocytes (CNS) and Schwan cells (PNS)
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