1. Nervous System Histology

2. In Lab Today:
Draw & identify the portions of a multipolar neuron from slides
Draw & differentiate between pseudounipolar, bipolar & multipolar neurons from slides
Identify the components of the nerve cross section using diagrams & slides
Identify the portions of a multipolar neuron from the models

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

4. Objective 1: Neuron Structure

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

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

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

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

9. 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
Schwann cell nucleus
myelin sheath
axon
neurilemma
Node of Ranvier

10. Gaps between successive Schwann cells along the length of the axon
Nodes of Ranvier -
Gaps between successive Schwann cells along the length of the axon
Microscopic Views

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

12. Spinal Cord Smear – Motor Neuron
What you need to draw and label
Cell Body
Spinal Cord Smear – Motor Neuron

13. Objective 2: Neuron Classification

14. A short process (axon) emerges from the cell body and divides into proximal and distal branches
>
Receptive Endings
Distal process
(toward periphery)
Proximal process
(toward CNS)
Has a single axon and a single dendrite attached to opposite sides of the cell body
<
dendrite
axon (branched)
>
Has multiple dendrites and a single axon
dendrites
axon

15. (Pseudo)unipolar neuron
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

16. Bipolar neurons Found in Example: Retina special sense organs
(eye, ear, nose, tongue)
Example: Retina

17. (Pseudo)uipolar neurons
HISTOLOGY
(Pseudo)uipolar neurons
Bipolar neurons
Multipolar neurons

18. Pseudounipolar cell bodies
in the dorsal root ganglion of a spinal nerve

19. Pseudounipolar cell bodies
Centrally located nuclei
Dorsal Root Ganglion
Spinal Cord
Pseudounipolar cell bodies

20. Bipolar neurons in the human retina

21. Bipolar neuron nuclei
axons

22. Note: Multipolar neurons have diverse morphologies
You do not need to memorize all these

23. Some Examples of Motor Neurons
Neurons from the spinal cord (smear)
Neuron from the cerebral cortex

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

25. Pyramidal cell
(Low Power – Cerebrum)

26. (Low Power - Cerebellum)
Purkinje cell
(Low Power - Cerebellum)

27. Recap: Neuron Classifications
Be able to identify each type of neuron by classification

28. Objective 3: Nerve Structures
Nerves are structures of the PNS that consist of axons and dendrites bundled together by connective tissues

29. NERVE
Epineurium: tough, fibrous connective tissue sheath surrounding a nerve
Perineurium: loose, areolar connective tissue sheath surrounding fascicles
Fascicle: a bundle of axons or dendrites
Endoneurium: delicate connective tissue wrapping around each nerve fiber; the endoneurium electrically insulates each nerve fiber

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

32. LAB ACTIVITY:
Draw and label the components of the nerve cross section