1. Nervous System Histology
Week 9
Human Body Explorer

2. Objective 1: Neuron Structure
Parts of a Neuron - animation
 Link

3. Breakdown 1 Dendrites (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)

4. Breakdown 2 Axon hillock Impulse direction Node of Ranvier Axon
Schwann cell
(one internode)
Neurilemma
(sheath of Schwann)

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

6. (secretory component)
Breakdown 3
Impulse
direction
Axon terminals
(secretory component)
Terminal branches
(Telodendria)

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

8. Breakdown 4
Axon Collateral

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

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. Objective 2: Neuron Classification

13. 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

14. (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

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

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

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

18. Pseudounipolar Cell Bodies
Centrally located nuclei
Dorsal Root Ganglion
Spinal Cord
Pseudounipolar Cell Bodies

19. Bipolar neurons in the human retina

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

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

22. Silver Stained Neuron in Gray Matter of spinal cord
Spinal Cord - Anterior Horn
Multipolar neuron
Glial cell nuclei
(supporting cells)

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

24. Pyramidal cell
(Low Power – Cerebrum)

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

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

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

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

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

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

32. QUICK REVIEW

33. On the Practical:
Identify the portions of the multipolar neuron from the models in lab
Identify the portions of the multipolar neuron from a prepared slide

34. Identify the structural class of these neurons:
pseudounipolar
bipolar
multipolar
multipolar

35. Identify the components of the nerve cross section
Epineurium
Perineurium
Fascicle
Endoneurium
(nerve fibers)