1. Biology 211 Anatomy & Physiology I
Cytology and Histology of the Nervous System

2. Brain
Spinal Cord
Central Nervous System (CNS) =
Peripheral Nervous System (PNS)
Nerves =

3. Recall: All organs are composed of, at most, four tissues
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
Nervous tissue: Excitable cells (neurons)
Nonexcitable (supporting) cells
Connective tissue: Meninges in central nervous system
Endoneurium
Perineurium in peripheral nervous system
Epineurium
Epithelium
found only in blood vessels
Muscle (smooth)

4. Cells of Nervous Tissue:
1) Excitable cells = Neurons
Carry electrical signals from one
place to another
Pass these signals to other cells
Nonexcitable cells
Glia in Central Nervous System
Satellite cells
Schwann cells
in Peripheral Nervous System

5. 1) Excitable cells = Neurons
Carry electrical signals from one place to another
Pass these signals to other cells
Found in either central
nervous system, peripheral
nervous system, or may
have parts in both
Do not divide
Long-lived
High metabolic rates

6. 1) Neurons Classified by: Location

7. 2) Neurons Classified by: Shape
Bipolar
Multipolar
Unipolar or
Pseudo-unipolar

8. Axon Terminals
Dendrites
Axon Hillock
Axon
Telodendria
Cell Body

9. Exception to this classification: Unipolar or pseudo-unipolar neurons
Cell body
Single process
Dendrites
Axon branches
Telodendria and axon terminals

11. Excitatory synapses

12. Excitatory synapses
Inhibitory synapses

13. Cells of Nervous Tissue:
1) Excitable cells = Neurons
Carry electrical signals from one place to another
Pass these signals to other cells
2) Nonexcitable cells
Do not carry electrical information
Support, nourish, protect neurons
May divide

14. Non-excitable cells
In PNS:
Satellite cells surround
neuron cell bodies
Schwann cells surround
cell processes
In CNS:
Four types of Glia

15. Glia: 4 types in central nervous system
1) Astrocytes
2) Oligodendrocytes:
3) Microglia:
4) Ependyma:

16. Glia: 1) Astrocytes: Regulate environment around neurons
by controlling the passage of molecules into and
out of capillaries, and by absorbing or secreting
ions from/into extracellular matrix

17. Glia: 2) Oligodendrocytes: Produce myelin sheaths
around axons of neurons in central nervous
system

18. Glia: 3) Microglia: Phagocytic. Remove degenerating
cells and foreign debris from central nervous
system

19. Glia: 4) Ependyma: Line fluid-filled ventricles within
central nervous system

20. Non-excitable cells of Peripheral Nervous System
1) Satellite cells surround and protect neuron cell bodies
in peripheral nervous system
Satellite Cells

21. Non-excitable cells of Peripheral Nervous System
2) Schwann cells produce myelin sheaths which
surround axons in peripheral nervous system
Schwann Cells
Nodes of Ranvier

23. Pathology of the Nonexcitable Cells
Loss of oligodendrocytes causes multiple sclerosis and a group of diseases called leukodystrophies
Injury to astrocytes, usually from toxic substances, leads to cerebral edema and swelling of the brain
Injury to Schwann cells causes degeneration of the neuron processes and prevents their healing and regrowth. It is also responsible for Guillain-Barre syndrome

24. Pathology of the Nonexcitable Cells
Tumors can arise from all four types of glia, and these tend to grow rapidly and destroy nearby regions of the brain or spinal cord
Astrocytoma
Ependymoma
Tumors can also arise from satellite cells or Schwann cells, compressing and destroying the neurons they surround
Schwannoma