1. Histology of Nervous Tissue
Lab Exercise 13
Histology of Nervous Tissue
Portland Community College
BI 231

2. Major divisions of the nervous system
Central nervous system (CNS)- brain and spinal cord
Peripheral nervous system (PNS)- comprises all nerves that connect the brain and spinal cord to muscles, glands and receptors.

3. Nerves Cranial nerves are those that are connected to the brain
Spinal nerves are connected to the spinal cord.
Both contain sensory information from receptors and send motor signals.

4. Motor (Efferent) Neurons Efferent = Away from CNS
These are neurons that carry information from CNS to the body
Groups of axons running together are the Nerves when they are outside the CNS and Tracts inside the brain and spinal cord
The cell bodies are clustered in groups in the CNS and are called nuclei
Brain gray matter is made up of millions of nuclei.
It is gray because there is no myelin around the cell bodies
These axons exit the spinal cord on the ventral side

5. Motor (efferent) division of PNS
Somatic nervous system- contains efferent neurons extending from the CNS to skeletal muscle.
Autonomic nervous system- contains efferent neurons from CNS to smooth muscle, cardiac muscle and glands

6. Sensory (Afferent) Neurons Afferent = Toward the CNS
These carry sensory information from the body to the CNS (brain and spinal cord)
Their axons run in the same group as the motor neurons (nerves=groups of axons)
Their cell bodies are clustered outside of the spinal cord and are called ganglia
These axons enter the spinal cord on the dorsal side

7. Sensory (afferent) division
Afferent neurons that receive stimuli from somatic sensory receptors that detect general sensations
Receive stimuli from visceral sensory receptors
Special sensory receptors that detect special sensations (smell, taste, vision, hearing, equilibrium)

8. Organization of nervous system

9. Neuron

10. Myelin Some axons are surrounded by a myelin sheath
Multilayered lipid and protein covering formed by Schwann cells around axons
Oligodendrocytes in the CNS
The covering is the plasma membrane of the Schwann Cell
The Schwann Cell can cover more than one axon
Insulates axon

11. Nodes of Ranvier
Areas between Schwann Cells that do not contain Myelin
Involved in saltatory conduction

12. Dendrite
Neuron Cell Body
Nucleus
Axon Hillock
Axon

13. Axon Terminal (Synaptic end bulbs)
Schwann Cell
Axon
Node of Ranvier
Myelin Sheath
Telodendria
Axon Terminal (Synaptic end bulbs)

14. Classification
Sensory (afferent) neurons conduct nerve impulses from sensory receptors
Motor ( efferent) neurons conduct nerve impulses from the CNS
Interneurons form links between sensory and motor

15. Multipolar Neuron Most common type of neuron
Cell Body
Axon
Dendrites (trigger zone)
Most common type of neuron
Interneurons and motor neurons

16. Anaxonic Neurons
A small number of multipolar neurons contain only dendrites or
Cannot distinguish dendrites from axons
Functions are poorly understood.

17. Bipolar Neuron Location: special senses (smell, vision, hearing)
Dendrite (trigger zone)
Axon
Cell Body
Location: special senses (smell, vision, hearing)

18. Unipolar Neuron All are sensory afferent
Dendrite (trigger zone)
Axon
Cell Body
All are sensory afferent
Cell bodies are located in the dorsal root ganglia

19. Association or Interneurons
Neurons between the afferent and efferent neurons.
Are only in the CNS

20. Neuron Perineurium Fascicle Epineurium Axon Myelin Sheath
Node of Ranvier
Perineurium
Fascicle
Epineurium

21. Glial Cells Associated with neurons Provide Supportive scaffolding
Segregate and insulate neurons
Outnumber neurons by 10 to 1

22. Supporting Cells in the CNS Astrocytes
Star Shaped
Many functions
Regulates levels of O2 ,
& CO2
Exchanges between capillaries and neurons (blood-brain barrier)
Nutrient transfer

23. Supporting Cells in the CNS Microglia
Protect CNS from disease-causing organisms
Monitor the health of neurons
Act as phagocytes eating microorganisms and debris

24. Ependymal cells
These cells are modified epithelial cells that line the ventricles of the brain and central canal of spinal cord.
Facilitate circulation of CSF

25. Supporting Cells in the CNS Oligodendrocytes
Produce the myelin sheath which provides the electrical insulation for some neurons in the CNS

26. Supporting Cells in the PNS Schwann Cells
Form the myelin sheath around axons in the PNS

27. Satellite cells
Surround neuron cell bodies in peripheral ganglia and regulate levels of oxygen, carbon dioxide and nutrients.

28. The synapse
Axons generate action potentials which are transmitted across synapses
Formed by presynaptic membrane and postsynaptic membrane on an effector cell
The synaptic cleft is a narrow space that separates these

29. The End
The End