1. Psychology 304: Brain and Behaviour Lecture 10

2. The Cells of the Nervous System
1. What is the structure of the neuron?
2. What are glial cells?

3. By the end of today’s class, you should be able to:
1. describe the external structural features of the neuron.
2. describe the internal structural features of the neuron.
3. distinguish between unipolar, bipolar, and multipolar neurons.
4. identify the types and functions of glial cells.

4. What is the structure of the neuron?
The external structure of the neuron is characterized by eight features:

5. Cell body: The metabolic center of the neuron. Also called the soma.
Cell membrane: A semipermeable membrane that encloses the neuron.
Axon: A long, narrow extension that projects from the cell body.
Axon hillock: The cone-shaped region at the junction between the axon and cell body.

6. Myelin sheath: Fatty insulation surrounding the axon.
Nodes of Ranvier: Gaps between sections of myelin.
Dendrite: A short extension emanating from the cell body that receives contacts from other neurons.
Terminal buttons (axon terminals): Button-like endings on axon branches that contain chemicals for communication between cells (i.e., neurotransmitters).

7. External Features of a Typical Neuron
Dendrite
Terminal button
Cell body
Nodes of Ranvier
Axon
Cell membrane
Myelin sheath
Axon hillock
External Features of a Typical Neuron

8. Image of a Neuron Produced by Light Microscopy

9. The internal structure of the neuron is characterized by
The internal structure of the neuron is characterized by nine features:

10. Nucleus: The spherical DNA-containing structure of the cell body.
Cytoplasm: The clear internal fluid of a cell.
Mitochondria: Sites of energy production and release.
Endoplasmic reticulum: A system of folded membranes; Rough portions are involved in protein synthesis. Smooth portions are involved in fat synthesis.

11. Ribosomes: Located on rough endoplasmic reticulum
Ribosomes: Located on rough endoplasmic reticulum. Cellular structures on which proteins are synthesized.
Golgi complex: A system of membranes that packages molecules in vesicles.
Microtubules: Tubules that allow for the rapid transport of material throughout neurons.

12. Endoplasmic reticulum
Golgi complex
Endoplasmic reticulum
Ribosomes
Internal Features of the Cell Body

13. Photomicrograph of a Neuron Cell Body

14. Synaptic vesicles: Spherical membrane packages that store neurotransmitter molecules ready for release from the terminal button.
Neurotransmitters: Molecules that are released from the terminal buttons of active neurons and influence the activity of other cells.

15. Internal Features of the Terminal Button
Microtubule
Terminal button
Mitochondrion
Synaptic vesicles
Neurotransmitters
Internal Features of the Terminal Button

16. Images of Synaptic Vesicles Produced by Electron Micrography
Synaptic contact
Mitochondria
Synaptic vesicles
Images of Synaptic Vesicles Produced by Electron Micrography

17. There are three primary classes of neurons:
1. Unipolar (monopolar) neurons: Have one projection extending from the cell body.
2. Bipolar neurons: Have two projections extending from the cell body.
3. Mutlipolar neurons: Have more than two projections extending from the cell body (e.g., one axon and many dendrites). The most common type of neuron found in the CNS.

18. Bipolar neuron 1. 2. Multipolar neuron 3. Unipolar neuron
Dendrites
Axon
Bipolar neuron 1. 2.
Multipolar neuron 3.
Unipolar neuron
Classes of Neurons

19. Neurons vary substantially in size and complexity.
In contrast to small neurons, large neurons detect and transmit more information and cover greater distances.

20. Variability in the Size and Complexity of Neurons

21. What are glial cells?
Found throughout the nervous system; more common than neurons.
Surround and support neurons, control the supply of nutrients to neurons, assisting in the exchange of chemicals between neurons, destroy and remove neurons damaged by disease or injury.
Four types of glial cells have been identified:

22. 1. Oligodendrocytes: Produce the myelin sheaths that
1. Oligodendrocytes: Produce the myelin sheaths that surround the axons of neurons of the CNS.
Extensions from a single oligodendrocyte wrap around the axons of multiple neurons.

23. Myelination of Axons in the CNS by Oligodendrocytes

24. 2. Schwann cells: Produce the myelin sheaths that
2. Schwann cells: Produce the myelin sheaths that surround the axons of neurons of the PNS.
Multiple Schwann cells wrap around the axon of a single neuron. .

25. Myelination of Axons in the CNS by Oligodendrocytes vs
Myelination of Axons in the CNS by Oligodendrocytes vs. Myelination of Axons in the PNS by Schwann Cells

26. 3. Microglia: The smallest glial cells. Trigger
3. Microglia: The smallest glial cells. Trigger inflammatory responses to brain damage and remove injured or dead neurons.
4. Astrocytes: The largest glial cells. Hold neurons in place, provide nutrients (e.g., lactate) to neurons, limit the “dispersion” of neurotransmitters released by terminal buttons, and remove injured or dead neurons.

27. Microglia

28. Microglia

29. Structure of Astrocytes

30. Microglia
Astrocytes

31. The Cells of the Nervous System
1. What is the structure of the neuron?
2. What are glial cells?