1. Graduate Microanatomy Spring 1999 Sandra H. Bolanos
Nervous Tissue
Graduate Microanatomy Spring 1999
Sandra H. Bolanos

3. Central Nervous System
Brain
Spinal Cord

4. Brain Cranium (brain case) Cortex Gray matter Nerve cell bodies
Interior Portion
White matter
Axons
Ventricles
CSF

5. Spinal Cord Occupies two-thirds of the vertebral canal
Enveloped by meninges
Cervical and lumbar enlargements
Gray matter centrally located

6. Meninges 3 layers of connective tissue membranes
Surround and protect brain and spinal cord
Pia Mater
Arachnoid
Dura Mater

7. Peripheral Nervous System
Nerves that emerge from central nervous system:
31 pairs of spinal nerves
12 pairs of cranial nerves

8. Autonomic Nervous System
Sympathetic
Parasympathetic

9. Cellular Composition of CNS
Neurons and their processes
Support cells:
Astrocytes
Oligodendrocytes
Ependymal cells
Microglia

10. Astrocytes
In developing NS, form structural framework to guide migration of developing neurons
In developed NS, form
structural scaffolding for
more specialized neural
elements
Clear ECM of by-products
of neural activity and
contain glycogen reserves
Extend foot processes around
blood capillaries

11. Blood Brain Barrier
Capillaries of the CNS not fenestrated and have intercellular tight junctions between endothelial cells
Highly resistant to passage of ions or small molecules
Do not exhibit transendothelial transport in small vesicles
Astrocytes may influence capillaries to express these unique properties

12. Oligodendrocytes Produce myelin within CNS
Each cell sends out several processes and myelinates several nearby axons

13. Ependymal Cells Epithelial-like Ciliated
Line cavities of brain ventricles and central canal of spinal cord forming sheets of cuboidal cells in contact with CSF

14. Microglia Specialized macrophages
In areas of injury, proliferate and become actively phagocytic in clearing cellular debris and ingesting damaged myelin

15. Composition of PNS
Ganglia - a peripheral collection of nerve cell bodies together with efferent and afferent axons and support cells
Nerves - a collection of axons linked together by support tissue into an anatomically defined trunk

16. Ganglia Sensory (spinal sensory ganglia)
Non-sensory (sympathetic or parasympathetic)
Dorsal root ganglia, cranial ganglia, autonomic ganglia
Neuron cell bodies, support cells, loose fibrocollagenous tissue

17. Nerves Motor Innervate skeletal muscle (CNS)
Innervate smooth muscle (PNS)
Sensory
Myelinated or Non-myelinated
Axons, Schwann cells, fibroblast cells, blood vessels

18. - 3 types of support tissue in a nerve trunk:
Endoneurium
Surrounds individual axons, their associated Schwann cells, and
capillary blood vessels
Perineurium
Surrounds groups of axons and endoneurium to form fascicles
Epineurium
binds individual nerve fascicles into a
nerve trunk

19. Epi Peri Fascicle Endo Endoneurium Perineurium
Collagen fibers that are longitudinally oriented
ECM rich in GAGs and sparse fibroblasts
Perineurium
7-8 concentric layers of epithelium-like flattened cells separated by
layers of collagen and joined by junctional complexes
Each layer of cells surrounded by an external lamina
Epineurium
Outer sheath of loose fibrocollagenous tissue
May also include adipose tissue and muscular artery that supplies the nerve trunk
Epi
Peri
Fascicle
Endo

20. Schwann Cells
PNS
Myelinate only one axon

21. Neurons Gather information from sensory receptors
Process information and provide a memory
Generate appropriate signals to effector cells
Cell body, dendrites, axon, and synaptic bouton

22. Cell Body Pale-staining Conspicuous nucleolus Little heterochromatin
Nissl bodies
Golgi complex
Mitochondria
Lysosomes
Neurofilaments
Microfilaments
Microtubules

23. Dendrites Radiating processes of the cell body
Receive signals (synapses) from other neurons
Broader than axons
Extensive branching increases cell surface available for receiving signals from other neurons
Organelles similar to those of the perikaryon (no Golgi bodies)
As distance from cell body increases, smooth ER and NFs reduced but MTs and mitochondria still prominent

24. Axons A single long process capable of generating a nerve impulse
More slender and usually longer than dendrites
Branch at right angles
Can be quite long (spinal motor neurons that supply foot muscles 40 inches in length)
Axon Hillock is conical extension of cell body from which axon arises
Axoplasm lacks Nissl bodies

25. Branches as it approaches its end forming small expansions
Terminal boutons contact other cells to form a synapse
At synapse, chemicals or electrical signals pass from one neuron to another cell known as the effector cell
Neurotransmitters act rapidly and locally to activate their target cells and neuromodulators that regulate these events

26. Neuron Shapes

27. Neuron Types

28. Myelin Insulation minimizes leakage of current from membrane
speeds up conduction along axons
Reduction of electrical capacitance
wide axons lower capacitance than narrow ones
increases diameter of axons
increases speed of nerve conduction
Myelin-producing cells
Oligodendrocytes (CNS)
Schwann cells (PNS)
Nodes of Ranvier
space between each unit of myelin
increase efficiency of nerve conduction

29. Myelin

31. Synapses
Specialized region of contact where NT released from axon to stimulate another cell

33. Axonal Transport Anterograde or retrograde Fast or slow Microtubules
Motor proteins
Ca2+
ATP
Minus end
Plus end
Kinesin
Dynein