Histology slides Nervous Tissue Neuron & Glial Cells Disease-related

1. Nervous Tissue-
Neuron & Glial cells
Amy Alfy
Histology

2. Nervous System
The nervous system is organized into two (2) basic components:
● Central nervous system (CNS) – Brain and Spinal Cord
● Peripheral Nervous System (PNS) – 12 pairs Cranial Nerves, 31 pairs of
spinal nerves, ganglia
THE NERVE CELL
● The nerve cell is the basic unit of the nervous system.
● Nerve cells are called neurons.
● Nervous tissue is composed of two types of cells, neurons and glial cells.

3. 2 Types of Nerve Tissue
Neurons- Important in neural communication. Functional unit in both the CNS and PNS that transmit
electrical signals
Example: sensing, thinking, remembering, controlling muscle activity
Neuroglia- support, nourish and protect the neurons and maintain homeostasis
❖ Glial cells are supporting cells that surround and wrap the more delicate neurons
● Astrocytes
● Oligodendrocytes
● Ependymal cells
● Microglia
● Schwann cells
● Satellite cells

4. Neurons
● Neurons are the cells considered to be the basis
of nervous tissue.
● Responsible for the electrical signals that
communicate information about sensations,
and that produce movements in response to
those stimuli, along with inducing thought
processes within the brain.
● An important part of the function of neurons is
in their structure, or shape. The three-
dimensional shape of these cells makes the
immense numbers of connections within the
nervous system possible.

5. 3 Parts of Neuron
1) Dendrites- help to increase the surface area available for connections with the adjacent neurons and thus in receiving
incoming signals from them.
● Acquiring chemical impulse from other cells and neurons
● Converting the chemical signals into electrical impulses
● Carrying electrical impulses towards the next part of the neuron, the cell body
2) Cell body or soma- is the core and the largest portion of a neuron, and it is surrounded by a cell membrane that shields it
from its immediate surroundings while allowing it to communicate with the outside environment. They bind to all dendrites,
allowing all signals to be integrated. The cell body also contains the DNA, and allows for all of the cell's metabolic functions to
take place.
● Supporting and organizing the functions of the whole neuron
● Joining the signals received by the dendrites and passing them to the axons, the next part of the neuron
3) Axons- fine, elongated fiber-like extensions of the nerve cell membrane. Axons run from the cell body of one neuron until
the terminal of the next neuron.

6. Parts of the Axon
a) Axon hillock – The part of the axon which remains attached to the cell body or soma.
b) Myelin sheath – The layer of fatty acid produced from specialized cells called Schwann cells that
are wrapped around the axon.
c) Nodes of Ranvier – The gaps between the discontinuous myelin sheath that is running along the
axon.
● Axons help to receive signals from other neurons and transmit the outflow of the message to the
adjacent connected neurons and also to other muscles and glands by changing the electrical
potential of the cell membrane called the action potential.
● Myelin sheath insulates the axon and thus prevents shock similar to an insulated electric wire
● Myelin sheath also increases the speed of the flow of signals through the axon

9. Astrocytes
Astrocytes have many cytoplasmic processes that
terminate on blood vessels, neuronal cell bodies, axons
and synaptic terminals.
● Physical and metabolic support for neurons
● Detoxification
● Guidance during migration
● Regulation of energy metabolism
● Electrical insulation (for unmyelinated axons)
● Transport of blood-borne material to the neuron
● Reaction to injury.

10. Ependymal cells
• Ependymal cells are columnar or cuboidal ciliated
cells that line the ventricles of the brain and central
canal of the spinal cord
• The ependymal cells line the walls of the ventricles
and form the specialized choroid plexus epithelium
which secretes the cerebrospinal fluid (CSF).

11. Microglia
● Microglia are resident cells of the brain that regulate brain development,
maintenance of neuronal networks, and injury repair.
● Microglia serve as brain macrophages but are distinct from other tissue
macrophages owing to their unique homeostatic phenotype and tight
regulation by the central nervous system (CNS) microenvironment.
● Responsible for the elimination of microbes, dead cells, redundant
synapses, protein aggregates, and other particulate and soluble antigens
that may endanger the CNS.

12. Satellite cells
• Satellite cells exert a trophic or supportive
effect on neurons, insulating, nourishing, and
regulating their microenvironments.
• Satellite cells are restricted to ganglia where
they cover and support the large neuronal cell
bodies

13. Oligodendrocytes
• Oligodendrocytes small round in shape that
produce the myelin sheaths around axons that
provide the electrical insulation for neurons in
the CNS.
• Oligodendrocytes are primarily responsible for
maintenance and generation of the myelin
sheath that surrounds axons.
• They also participate in axonal regulation and
the sculpting of higher order neuronal circuits.
Myelinated/ Unmyelinated axon of
oligo

14. Schwann cells
• Schwann cells are the major glial cell type in the
peripheral nervous system (PNS) . They play
essential roles in the development, maintenance,
& function.
• One Schwann cell forms myelin around a
segment of one axon

15. Diseases
● Alzheimer’s disease affects these cells and chemicals, disturbing memory,
impairing thinking and causing behaviour changes over time.
● Multiple sclerosis (MS) is a chronic disease that affects the central nervous
system. MS means there is damage to the protective sheath (known as myelin)
that surrounds the nerve fibres in the brain and spinal cord. This damage causes
scars, or lesions, in the nervous system, meaning that the nerves can’t send
signals around the body properly.
● ALS : motor nerves, or motor neurons generate and die and slowly the muscles
become weaker and eventually leads to paralysis.
● Neurofibromatosis is a genetic condition characterised by the growth of
neurofibromas. These are a type of tumour that is usually benign, or non-
cancerous and can occur in any nerve cell in the body

16. Summary
CNS Glia PNS Glia Basic Function
Astrocyte Satellite cell Support
Oligodendrocyte Schwann cell Insulation, myelination
Microglia Immune surveillance
and phagocytosis
Ependymal cell Creating CSF

18. Resources
● https://www.sciencefacts.net/parts-of-a-neuron.html
● https://www.sciencedirect.com/topics/neuroscience/oligodendrocyte#:~:text=Oligodendrocytes%20are%20specialized%20glial%20cell
s,order%20neuronal%20circuits%20%5B51%5D.
● http://medcell.med.yale.edu/systems_cell_biology/nervous_system_lab.php
● https://opentextbc.ca/anatomyandphysiologyopenstax/chapter/nervous-
tissue/#:~:text=Nervous%20tissue%20is%20composed%20of,that%20the%20nervous%20system%20provides.
● sciencefacts.net/parts-of-a-neuron.html
● https://diffzi.com/neurons-vs-neuroglia/
● https://www.healthdirect.gov.au/neurofibromatosis
● http://blogs.berkshirecc.edu/bccoer/mammalian-histology-nervous-tissue/
● https://www.annualreviews.org/doi/abs/10.1146/annurev-immunol-051116-
052358#:~:text=Microglia%20are%20resident%20cells%20of,neuronal%20networks%2C%20and%20injury%20repair.
● https://www.healthdirect.gov.au/motor-neurone-disease-mnd
● https://www.healthdirect.gov.au/nervous-system-diseases
● https://neuropathology-web.org/chapter1/chapter1cOligodendroglia.html
● https://learn.chm.msu.edu/neuropath/content/cytopathology/CP_10.html
● Dr. Dr. Nikhila Chelikam histology slides- Development of Nerve Tissue & Neurons
Thank you for listening!