1. Nervous System Histology
Week 9 SB

2. What is a neuron?
Neuron = Nerve cell
Reflex Arc

3. Objective 1: Neuron Structure

4. Multipolar Neuron model
Main parts of a neuron
Dendrites (receive)  Cell Body (process)  Axon (send)  Axon Terminals (transfer)
Cell Body
Axon Terminals
Multipolar Neuron model

5. Dendrites and Cell Body
(receptive
regions)
Cell body (Soma)
(biosynthetic center
and receptive region)
Neuron cell body
Nissl bodies
(rough ER)
Dendrite
Neurofibrils
Impulse
direction
Nucleus
Nucleolus
Axon
(impulse generating
and conducting region)

6. Axon Axon hillock Impulse direction Node of Ranvier Axon Schwann cell
(one internode)
Neurilemma
(sheath of Schwann)

7. Schwann cells - supporting cells of the PNS that myelinate axons
Myelin sheath – whitish lipoprotein that surrounds and insulates the axon (nerve fiber)
Neurilemma - external layer containing bulk of cytoplasm with nucleus and organelles (cell membrane)
Schwann cell nucleus
myelin sheath
axon
neurilemma
Node of Ranvier

8. Schwann cells myelinate axons
Gaps between successive Schwann cells along the length of the axon are nodes of Ranvier

9. What you need to draw and label
Axon
Node of Ranvier
Neurilemma

10. Neuron Pathology: Multiple Sclerosis
MS is thought to be an autoimmune disease in which the myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas are also known as plaques or lesions. Sometimes the nerve fiber itself is damaged or broken.
Myelin not only protects nerve fibers, but makes their job possible. When myelin or the nerve fiber is destroyed or damaged, the ability of the nerves to conduct electrical impulses to and from the brain is disrupted, and this produces the various symptoms of MS.

11. (secretory component)
Axon Terminals
Impulse
direction
Axon terminals
(secretory component)
Terminal branches
(Telodendria)

12. Remember this?
Axon (branches)
Muscle fibers
Axon terminals

13. Axon Collateral
Axon Collateral

14. Spinal Cord Smear – Motor Neuron
What you need to draw and label
(Nuclei)
Cell Body
Spinal Cord Smear – Motor Neuron

15. Objective 2: Neuron Classification

16. Pseudounipolar (unipolar) neurons
include most sensory neurons
have a short process which emerges from the cell body and divides into proximal and distal branches
soma
Distal process (toward periphery)
Proximal process (toward CNS)

17. Pseudounipolar Cell Bodies in the Dorsal Root Ganglion of a Spinal Nerve

18. Red arrows - Central Nuclei of Sensory Neurons
“This is a low power slide of the Dorsal Root Ganglion. The key to knowing that you are looking at Neurons in the DRG is by looking for the CENTRALLY LOCATED NUCLEI, indicated by the Red arrows. These large neurons are Pseudounipolar, Sensory (Afferent) Neurons. They are responsible for conveying information to the Central Nervous System. You can tell that these Neurons have huge cell bodies. These are some of the largest cells in the body. The larger the cell body, the further away the information is coming from.”
Red arrows - Central Nuclei of Sensory Neurons
UMDNJ histsweb

19. Bipolar neurons are found in special sense organs (eye, ear)
Human retina
are found in special sense organs (eye, ear)
have a single axon & a single dendrite which are attached to opposite sides of the cell body
bipolar neurons
dendrite
axon (branched)

20. Multipolar neurons:
include most neurons including all motor neurons and most CNS neurons
have multiple dendrites and a single axon
Purkinje cell of the cerebellum
Pyramidal cell of the hippocampus
Neuron from the cerebral cortex

21. Silver Stained Neuron In Gray Matter

22. Spinal Cord - Anterior Horn
Glial cell nuclei Multipolar neuron

23. Multipolar neurons you will be drawing
Pyramidal cell
Hippocampus & Cerebral cortex
Purkinje cell Cerebellum

24. (Pseudo)unipolar neuron Multipolar neurons
Most sensory neurons
Cell body located in
Dorsal Root Ganglion
(spinal nerves)
Multipolar neurons
Most neurons
Most CNS neurons (interneurons)
All motor neurons
Cell bodies located in
Spinal cord & Brain

25. Objective 3: Nerves
Nerves are structures of the peripheral nervous system (PNS) that consist of axons and dendrites bundled together by connective tissue

26. Epineurium:. tough, fibrous connective. tissue sheath surrounding
Epineurium: tough, fibrous connective tissue sheath surrounding a nerve
Perineurium: loose areolar connective tissue sheath surrounding a fascicle (a bundle of axons or dendrites)
Endoneurium: delicate connective tissue wrapping around each nerve fiber which electrically insulates each nerve fiber

27. Electron micrograph image
Endoneurium
Perineurium
Nerve fiber (axon)
Fascicle
Epineurium
Electron micrograph image

28. a = epineurium b= perineurium
                                                                           

29. perineurium
endoneurium
axon

30. EN = endoneurium Ax = axon
NR = node of Ranvier My = myelin sheath