1. Neurons & Glia
Lecture 5

2. Nature of the Nervous System
Camillo Golgi
The Synctium
continuous network
no gaps ~

3. Nature of the Nervous System
Santiago Ramon y Cajal
The Neuron Doctrine
discrete cells
communication across gaps
synapses ~

4. Nature of the Nervous System
Golgi won
Proved himself wrong
Golgi Stain - silver chromate
Supported Neuron Doctrine
Golgi & Cajal shared Nobel Prize (1906) ~

5. NEURONS Basic functional unit of N.S. Specialized cell
All cells have same basic properties
information processing
Transmits
Integrates
Stores
Regulation of behavior ~

7. Information Transmission

8. Integrates information~
Receives information
Integrates information~
Stimuli

9. Axon carries information away from soma
Electrical signal
Axon terminal releases chemical message~

10. Neuron Classification
Categories overlap ~

11. Shorthand

12. By function (connections)
Sensory
Motor
Interneuron

13. By morphology (# of neurites)
Multipolar
Bipolar
Unipolar

14. By Morphology By Dendrite Structure Pyramidal Stellate
Dendritic Spines
Spiny or Aspinous ~

15. By Axon Diameter Sensory afferents Size: large ---> small
Aa, Ab, Ad, C
C: small, unmyelinated
pain & temperature
Aa:
not associated with skin receptors
proprioceptors in muscle ~

16. Primary Afferents Speed of conduction larger is faster
myelinated faster
slowest: C fibers ~

17. Other Classification Schemes
Axon length
Golgi Type I - long
Golgi Type II - short (local signaling)
Chemistry
neurotransmitter released ~

18. Neurons vs. Nerves Neurons - cells microscopic
Nerves - bundles of axons
seen with naked eye ~

19. Glia
Neural Support Cells

20. Astrocytes Provide physical support
Regulating chemical content of extracellular fluid
localizes neurotransmitters
K+ concentration
Blood-brain Barrier ~

21. Blood-Brain Barrier
astrocytes
Typical
Capillary
Brain
Capillary

22. BBB: Function Maintains stable brain environment
large fluctuations in periphery
Barrier to poisons
Retains neurotransmtters & other chemicals
Regulates nutrient supplies
glucose levels
active transport ~

23. Myelin Sheath

24. Myelin Wrap around axon Saltatory Conduction faster transmission
CNS: oligodendroglia
or oligodendrocytes
PNS: Schwann cells ~

25. Other non-neuronal cells
Microglia
phagocytosis
immune-like function
Ependymal cells
line walls of ventricles
role in cell migration during development ~

26. Membrane Structure Barrier Compartmentalization Semipermeable
selectively leaky
Fluid Mosaic Model
Phospholipids
Proteins ~

27. <------- Phosphate head
Phospholipids
< Phosphate head
hydrophilic
< Lipid tails
hydrophobic

28. Phospholipid Bilayer Hydrophilic heads ----->
Hydrophobic tails ----->

29. Membrane
H20 out & in
Pores~
H2O
H2O

30. Membrane Proteins Channels Pumps active transport
Receptor protein sites
bind messenger molecules
Transducer proteins:
2d messenger systems
Structural proteins
form junctions with other neurons ~

31. Membrane Proteins: Ionophores
Ions Channels
Nongated
always open
Gated
chemically-gated
electrically-gated
mechanically-gated ~

32. Chemically-Gated Channels
ligand-gated
Ionotropic
receptor protein = channel
direct control ---> fast
Metabotropic
second messenger system
indirect ---> slow ~

33. Membrane Proteins
OUTSIDE
INSIDE

34. Membrane Proteins
OUTSIDE
INSIDE

35. Metabolic pumps Membrane proteins Pump ions require energy Na+ - K+
Ca++ (calcium)
Also various molecules
nutrients
neurotransmitters ~