Download Nerve Cross Section

LABORATORY
9
Nervous System Histology
Objectives
1.
Identify the following portions of a multipolar neuron using a diagram, a model or a
prepared slide:
cell body (soma, perikaryon)
nucleus
Schwann cell
myelin sheath
axon collateral
axon
dendrite
Nissl bodies
axon hillock
node of Ranvier
neurofibril
neurilemma
telodendria (terminal branches)
axonal terminals (synaptic knobs, boutons)
2.
Differentiate between pseudounipolar neurons, bipolar neurons and multipolar neurons
using diagrams, models and prepared slides.
3.
Identify the following components of a cross sectioned nerve using diagrams and
prepared slides: myelin sheath, nerve fibers, fascicles, endoneurium, perineurium and
epineurium
Introduction
The functional unit of the nervous system is the neuron, a cell that is capable of
generating and propagating electrical signals in the form of action potentials. Neurons
can be found in the central nervous system (brain and spinal cord) and in the nerves of
the peripheral nervous system.
All neurons have three essential components: a cell body (soma), one or more
dendrites and a single axon. Neurons can be structurally classified as unipolar (having
a single projection from the cell body), bipolar (having two projections from the cell
body) of multipolar (having many projections from the cell body).
Neurons are supported structurally and functionally by cells called neuroglia (glial cells).
An example of a glial cell is a Schwann cell which produces an insulating myelin sheath
for the neurons of the peripheral nervous system.
A nerve is a bundle of axons that is found in the peripheral nervous system. These
axons are bundled into fascicles and are supported by a number of connective tissue
wrappings. The endoneurium is a delicate layer of loose connective tissue that
surrounds individual axons within a fascicle and electrically insulates each axon. The
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perineurium, a coarser connective tissue wrapping, surrounds the fascicles within the
nerve. The entire nerve is surrounded by an epineurium, which is a strong, dense layer
of fibrous connective tissue.
Materials
1. Each student should have a compound microscope.
2. Each pair of students should have:
Lens paper
Immersion oil
Lens cleaner
Box of prepared slides
Colored pencils
3. Class materials to be shared by students:
Three dimensional models of neurons
Charts of nervous system histology
Activity 1:
Resources:
The Structure of Multipolar Neurons
Textbook:
Photographic Atlas:
pages 140, 390 – 393
page 27 (Figures 3.41)
page 28 (Figures 3.44, 3.45)
page 102 (Figures 9.2, 9.3)
1. Identify the following components of a multipolar neuron on a three dimensional model and
on diagrams:
cell body (soma, perikaryon)
nucleus
Schwann cell
myelin sheath
axon collateral
axon
dendrite
Nissl bodies
axon hillock
node of Ranvier
neurofibril
neurilemma
telodendria (terminal branches)
axonal terminals (synaptic knobs, boutons)
1. Observe a prepared slide of an ox spinal cord smear. Select one neuron to study and
identify the cell body, nucleus, nucleolus and Nissl bodies. Try to differentiate between the
axon and dendrites. Sketch the neuron on the laboratory worksheet.
Note that the cytoplasm is coarsely textured with dark staining Nissl bodies (rough
endoplasmic reticulum). A large nucleus contains a prominent “Owl’s eye” nucleolus. A thin
axon emerges from the cell body at a conical shaped axon hillock. Both the axon and axon
hillock lack ribosomes and may be recognizable because of their pale staining cytoplasm. It
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is also possible that the axon is attached to the top or the bottom of the cell body and is
therefore not in your field of view.
2. Observe a prepared slide of myelinated nerve fibers. Identify the nodes of Ranvier, axon
(axis cylinder), Schwann cell nuclei and myelin sheath. Sketch the nerve fiber on the
laboratory worksheet.
Activity 2:
Resources:
Structural Classification of Neurons
Textbook:
Photographic Atlas:
pages 393-395; 550
page 117 (Figure 11.4)
page 118 (Figure 11.6)
1. Observe prepared slides of pyramidal cells (cerebral cortex) and purkinje cells (cerebellum),
and make sketches on your lab worksheet. Both are examples of multipolar neurons of the
central nervous system.
Pyramidal cells were named because of the shape of their cell body in specimens’ sectioned
perpendicular to the brain surface. The apex of the pyramid points to the brain surface.
Multiple dendrites emerge from the apex and the corners of the pyramid. A single axon
emerges from the base and travels deep into brain tissue.
Purkinje cells are located in the cortex of the cerebellum between its granular and molecular
layers. Purkinje cells have large cell bodies, a massive array of finely branching dendrites
that extend towards the surface, and a single small axon that extends into deeper portions
of the cerebellum.
2. Observe a prepared slide of the retina (eye) and locate the bipolar cells. Make a sketch on
your lab worksheet.
Note: It is fairly easy to identify the bipolar cell nuclei but more difficult to distinctly see the
axons and dendrites attached to the cell bodies.
3. Observe a prepared slide of a spinal cord section and locate the dorsal root ganglion.
Located within the dorsal root ganglion are the cell bodies of pseudounipolar neurons.
Make a labeled sketch on your laboratory worksheet.
Note: The cell bodies of these neurons are large, rounded with pale cytoplasm and
prominent nuclei and nucleoli. The cell bodies are surrounded by a layer of satellite cells.
Activity 3:
Resources:
Nerve Histology
Textbook:
Photographic Atlas:
pages 490-491
page 27 (Figures 3.40, 3.41,3.43)
Observe a prepared slide of a nerve in cross section and identify the following:
axon, myelin sheath (if visible), endoneurium, fascicle, perineurium and epineurium.
Make a labeled sketch on your lab worksheet.
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Checklist:
Neuron Structures
Cell body (soma, perikaryon)
Model/Diagram
____________
Prepared Slide
____________
Nissl bodies
____________
____________
Nucleus
____________
____________
Nucleolus
____________
____________
Dendrites
____________
____________
Axon Hillock
____________
____________
Axon
____________
____________
Schwann cell
____________
____________
Myelin sheath
____________
____________
Node of Ranvier
____________
____________
Axon collateral
____________
NA
Neurofibril
____________
NA
Neurilemma
____________
NA
Telodendria (Terminal branches)
____________
NA
Axon terminals (synaptic knobs,
boutons)
____________
NA
A.
Structural Classes of Neurons
____
Multipolar neuron (Pyramidal cell)
____
Multipolar neuron (Purkinje cell)
____
Bipolar neuron (retina)
____
Pseudounipolar neuron (dorsal root ganglia)
B.
Peripheral Nerve Anatomy
____
axon
____
endoneurium
____
fascicle
____
perineurium
____
epineurium
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Lab 9 Worksheet
Name:
Score:
Neuron
Total Magnification:
___________________
___________________
Nerve Fiber
____________
Total Magnification:
Label the nucleus, soma, nucleolus,
and, if possible, axon and dendrites
________
Label the nodes of Ranvier, axon,
and neurilemma
Pyramidal Cell (mulitpolar neuron)
Purkinje Cell (mulitpolar neuron)
Total magnification: ___________
Label the soma, nucleus, processes
Total magnification: _________
Label the soma, nucleus, processes
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Retina (Bipolar neuron)
Dorsal Root Ganglion (Unipolar neuron)
Total magnification: _________
Label the bipolar cell layer
Total magnification: __________
Label the soma and nucleus
Nerve Cross Section
Total magnification:
____________
Label the nerve fiber, endoneurium,
fascicle, perineurium, and epineurium
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Post lab worksheet lab 9
1. Label the structures of the neuron
2. Match the term with the description:
a.
b.
c.
d.
e.
neurofibril
Schwann cell
axon hillock
dendrite
Nissl bodies
f. axon
g. telodendria
h. node of Ranvier
i. axon terminal
j. soma
____
rough endoplasmic reticulum found in the cell body; also called
chromatophilic substance because of its affinity for basic dyes
____
distal knoblike endings of terminal branches that store neurotransmitter
____
neuronal process that acts as a receptive area for incoming stimuli
____
neuroglial cell that surrounds and forms myelin around larger nerve fibers in
the peripheral nervous system
____
biosynthetic center of a neuron; contains the nucleus, nucleolus and ribosomes
____
terminal branches of an axon
____
gaps in a myelin sheath
____
bundles of intermediate filaments that, along with microtubules, help to maintain the
shape of a neuron
____
the cone shaped area of the cell body that gives rise to an axon
____
neuronal process that generates action potentials and propagates them,
typically away from the cell body
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3. What is a nerve?
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
4. Match the term with its description. Each term can be used more than once.
a. mulitpolar neuron
b. bipolar neuron
c. unipolar neuron (pseudounipolar neuron)
____
sensory neurons of the peripheral nervous system in which a single process is
attached to the cell body; the process divides to form a peripheral process
and a central process
____
major type of neuron in the central nervous system
____
has two processes attached to the cell body, a single axon and a single dendrite
____
has a single axon and two or more dendrites attached to the cell body
____
act as receptor cells for special sense organs, such as the eye and nose
____
act as motor (efferent) neurons, transmitting impulses away from the central
nervous system to effectors
5. What is the location of each nerve connective tissue layer listed below?
Endoneurium:
_________________________________________________
Epineurium:
_________________________________________________
Perineurium:
_________________________________________________
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