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Nervous Tissue. Graduate Microanatomy Spring 1999 Sandra H. Bolanos. Central Nervous System. Brain Spinal Cord. Brain. Cranium (brain case) Cortex Gray matter Nerve cell bodies Interior Portion White matter Axons Ventricles CSF. Spinal Cord.

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nervous tissue

Nervous Tissue

Graduate Microanatomy Spring 1999

Sandra H. Bolanos

central nervous system
Central Nervous System
  • Brain
  • Spinal Cord
brain
Brain
  • Cranium (brain case)
  • Cortex

Gray matter

Nerve cell bodies

  • Interior Portion

White matter

Axons

Ventricles

CSF

spinal cord
Spinal Cord
  • Occupies two-thirds of the vertebral canal
  • Enveloped by meninges
  • Cervical and lumbar enlargements
  • Gray matter centrally located
meninges
Meninges
  • 3 layers of connective tissue membranes
  • Surround and protect brain and spinal cord

Pia Mater

Arachnoid

Dura Mater

peripheral nervous system
Peripheral Nervous System

31 pairs of spinal nerves

12 pairs of cranial nerves

  • Nerves that emerge from central nervous system:
cellular composition of cns
Cellular Composition of CNS
  • Neurons and their processes
  • Support cells:

Astrocytes

Oligodendrocytes

Ependymal cells

Microglia

astrocytes
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
blood brain barrier
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
oligodendrocytes
Oligodendrocytes
  • Produce myelin within CNS
  • Each cell sends out several processes and myelinates several nearby axons
ependymal cells
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
microglia
Microglia
  • Specialized macrophages
  • In areas of injury, proliferate and become actively phagocytic in clearing cellular debris and ingesting damaged myelin
composition of pns
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
ganglia
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
nerves
Nerves
  • Motor

Innervate skeletal muscle (CNS)

Innervate smooth muscle (PNS)

  • Sensory
  • Myelinated or Non-myelinated
  • Axons, Schwann cells, fibroblast cells, blood vessels
3 types of support tissue in a nerve trunk
- 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

slide19
Endoneurium

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

schwann cells
Schwann Cells
  • PNS
  • Myelinate only one axon
neurons
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
cell body
Cell Body
  • Pale-staining
  • Conspicuous nucleolus
  • Little heterochromatin
  • Nissl bodies
  • Golgi complex
  • Mitochondria
  • Lysosomes
  • Neurofilaments
  • Microfilaments
  • Microtubules
dendrites
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
axons
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
slide25
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
myelin
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

synapses
Synapses
  • Specialized region of contact where NT released from axon to stimulate another cell
axonal transport
Axonal Transport
  • Anterograde or retrograde
  • Fast or slow
  • Microtubules
  • Motor proteins
  • Ca2+
  • ATP

Minus end

Plus end

Kinesin

Dynein