1. Chapter 2: Neurons and Glia
Neuroscience: Exploring the Brain, 4e
Chapter 2: Neurons and Glia

2. Introduction “Neurophilosophy” No separation of mind and brain
Glia and neurons
Glia insulate, support, and nourish neurons.
Neurons
Process information
Sense environmental changes
Communicate changes to other neurons
Command body response

3. The Neuron Doctrine Histology Microscopic study of tissue structure
Nissl stain
Facilitates the study of cytoarchitecture in the CNS

4. The Neuron Doctrine—(cont.)
Golgi stain (developed by Camillo Golgi) revealed two parts of neurons:
Soma and perikaryon
Neurites: axons and dendrites

5. Basic Parts of a Neuron

6. The Neuron Doctrine—(cont.)
Cajal’s contribution
Neural circuitry
Neurons communicate by contact, not continuity.
Neuron doctrine
Neurons adhere to cell theory.
Use of Golgi stain

7. Neurites in Contact, Not Continuity

8. The Prototypical Neuron
The soma
Cytosol: watery fluid inside the cell
Organelles: membrane-enclosed structures within the soma
Cytoplasm: contents within a cell membrane (e.g., organelles, excluding the nucleus)

9. The Prototypical Neuron—(cont.)
The nucleus
Gene expression
Transcription
RNA processing

10. Internal Structure of a Typical Neuron

11. The Prototypical Neuron—(cont.)
Neuronal genes, genetic variation, and genetic engineering
Neurons differ from other cells because of specific genes.
Sequencing of human genome
Genetic basis of many diseases of the nervous system
Role of genetic engineering and gene targeting

12. The Prototypical Neuron—(cont.)
The soma—(cont.)
Ribosomes the major site for protein synthesis
Rough endoplasmic reticulum

13. The Prototypical Neuron—(cont.)
The soma—(cont.)
Protein synthesis also on free ribosomes; polyribosomes

14. The Prototypical Neuron—(cont.)
The soma—(cont.)
Smooth ER and Golgi apparatus
Sites for preparing/sorting proteins for delivery to different cell regions (trafficking) and regulating substances

15. The Prototypical Neuron—(cont.)
The soma—(cont.)
Mitochondria
Site of cellular respiration (inhale and exhale)
Krebs cycle
ATP is cell’s energy source.

16. The Prototypical Neuron—(cont.)
The neuronal membrane
Barrier that encloses cytoplasm
~5 nm thick
Protein concentration in membrane varies.
Structure of discrete membrane regions influences neuronal function.

17. The Prototypical Neuron—(cont.)
The cytoskeleton
Not static
Internal scaffolding of neuronal membrane
Three structures
Microtubules
Microfilaments
Neurofilaments

18. The Prototypical Neuron—(cont.)
The axon
Axon hillock (beginning)
Axon proper (middle)
Axon terminal (end)
Differences between axon and soma
ER does not extend into axon.
Protein composition: unique

19. The Prototypical Neuron—(cont.)
The axon terminal
Differences between the cytoplasm of axon terminal and axon
No microtubules in terminal
Presence of synaptic vesicles
Abundance of membrane proteins
Large number of mitochondria

20. The Prototypical Neuron—(cont.)
The synapse
Synaptic transmission
Electrical-to-chemical-to- electrical transformation
Synaptic transmission dysfunction leads to mental disorders.

21. The Prototypical Neuron—(cont.)
Axoplasmic transport
Anterograde (soma to terminal) vs. retrograde (terminal to soma) transport

22. The Prototypical Neuron—(cont.)
Dendrites
“Antennae” of neurons
Dendritic tree
Synapse—receptors
Dendritic spines
Postsynaptic (receives signals from axon terminal)

23. Classifying Neurons Classification based on number of neurites
Single neurite
Unipolar
Two or more neurites
Bipolar: two
Multipolar: more than two

24. Classifying Neurons—(cont.)
Classification based on dendritic and somatic morphology
Stellate cells (star-shaped) and pyramidal cells (pyramid-shaped)
Spiny or aspinous

25. Classifying Neurons—(cont.)
Classification by connections within the CNS
Primary sensory neurons, motor neurons, interneurons
Classification based on axonal length
Golgi type I
Golgi type II

26. Classifying Neurons—(cont.)
Classification based on gene expression
Creation of transgenic mice
Example of “ChAT-Cre mice”
Green fluorescent protein
Classification based on neurotransmitter type

27. Glia Function of glia Support neuronal functions Astrocytes
Most numerous glia in the brain
Fill spaces between neurons
Influence neurite growth
Regulate chemical content of extracellular space
Astrocyte

28. Glia—(cont.) Myelinating glia Oligodendroglia (in CNS)
Schwann cells (in PNS)
Insulate axons
Cross section of
myelinated nerve fibers

29. Glia—(cont.) Myelinating glia—(cont.) Oligodendroglial cells
Node of Ranvier
Region where axonal membrane is exposed

30. Other Non-Neuronal Cells
Ependymal cells
Microglia as phagocytes (immune function)
Vasculature

31. Concluding Remarks
Structural characteristics of the neuron provide insight into how neurons and their different parts work.
Structure correlates with function.