1. Cytology
Nikon ©

2. Types of cell Neurons - nerve cells Glial cells 50:50 volume
100 billion
Glial cells
≈ 10 X neurons
50:50 volume
CNS vs PNS

3. Neuronal overview Basic function of a neuron Requirements:
Transmit information from one place to another
Requirements:
Structural
Functional

4. Neurons are polarized

5. Parts of a neuron Dendrites Soma Axon Axon terminal
receive information
Soma
synthesize stuff
electrical integration
Axon
information conduction
Axon terminal
transmit information

6. En masse
Segregation:
white
gray

7. Same but different Multipolar (typical) Bipolar Pseudo-unipolar
single axon
multiple dendrites
Bipolar
Pseudo-unipolar

8. Pseudounipolar neurons….
….are really bipolar

9. Classes of neurons Sensory Motor Interneurons Projection
Week 6 - somatosensation
Week 7 - motor

10. Synapses Dendritic shafts / spines inhibitory / excitatory (Week 4)
MAP2
synaptotagmin

11. Axons are long ≈ 5ft motor neuron (Sciatic nerve) ≈99% cytoplasm
How to accomplish fast signaling (week 4)?
How to maintain structure?
How to communicate between distant parts?

12. Axon growth cone
Cytoskeleton
(Ken Balazovich)

13. Cross section of dendrite
Neurofilaments
filamentous actin
Microtubules
Tubulin (10% brain protein)
substrate for axonal transport
MAPs

14. Active transport molecular motors Slow: Fast Retro Antero kinesin
few mm / day
Fast
< 400 mm /day
Retro
Antero
kinesin
dynein

15. Ribosomes: Nissl substance
In dendrites (not largely in axons)
Local protein synthesis at the base of spines - plasticity
(week 9)

16. High energy use 30-40 % total energy consumption at rest Mitochondria
Maintain ionic gradients
Protein synthesis
Axonal transport
Mitochondria
Site of oxidative metabolism - ATP
Brain exclusively dependent on glucose
Found throughout the perikaryon, dendrites, axons and in synaptic terminals

17. Other organelles Similar to other cells Nucleus: Golgi:
Only a few 1000 CNS specific genes - encode CNS proteins
Extensive RNA splicing
Golgi:
post-translational modification

18. Relationship to other cells

19. Brain Glue

20. Glial cells
Types
Roles
Phalloidin
Tubulin
DAPI

21. Special properties (Astrocytes) star-shaped & largely lack polarity?
No synapses but cells communicate through gap-junctions
Relatively low energy requirement; function well under anaerobic conditions
Remove glutamate and other amino-acids from extracellular space - de-toxify the brain
Form myelin to insulate axons
Serve numerous homeostatic functions
Can and do proliferate postnatally; tumors

22. Are astrocytes really star-shaped?
(Bushong et al., 2002)

23. Macroglia <=> Microglia
Classification
Macroglia <=> Microglia
Astrocyte
protoplasmic astrocyte (Type 1)
fibrous astrocyte (Type 2)
Radial glia - development (week 4)
Oligodendrocyte
Schwann cell

24. Microglia engulfing a dying oligodendrocyte:
phagocytotic cells in the nervous system
blood derived cells comparable to macrophages
remove debris from the brain following injury and constitute an important defense system against pathogens.

25. Radial glia
Development
neuronal guidance

26. Schwann cell
Myelination in the PNS

27. Myelin sheet
One-to-one

28. Gap junctions and disease
Charcot-Marie-Tooth disease
progressive loss of PNS axons - weakness, atrophy

29. Nodes of Ranvier

30. Saltatory conduction (week 4)

31. Oligodendrocytes

32. 1:10 to 1:50

33. Unmyelinated CNS fibers

34. End feet……
contacting blood vessels

35. Induce the blood-brain-barrier
Active transport
Astrocytic endfoot

36. Nervous system regeneration
The CNS does not regenerate while the PNS does
This is NOT due to differences in central and peripheral neurons but due to differences in their glia
CNS oligodendrocytes actively suppress regeneration
PNS Schwann cells promote it

37. Injury to the CNS
Reactive gliosis
Degenerating Neuron
Microglia

38. Buffering of extracellular ions
Extracellular space is very narrow
=> small ionic fluxes cause large concentration changes

39. From here to there…..

40. Territorial coverage
non-overlapping
(Bushong et al., 2002)

41. Astrocytic Glutamate transport
Around synapses

42. Transmitter “shuttle”

43. Glia versus neuron - difference?
excitability
(Bergles et al., 1997)