Lab Activity 12 Histology of Nervous Tissue Martini Chapter 12 Portland Community College BI 231.

Lab Activity 12

Histology of Nervous Tissue

Martini Chapter 12

Portland Community CollegeBI 231

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Neuron

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Myelin

• 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

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Nodes of Ranvier

• Areas between Schwann Cells that do not contain Myelin

• Involved in saltatory conduction

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Neuron Cell Body Nucleu

sAxon Hillock

Dendrite

Axon

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Myelin Sheath

Axon Node of Ranvier

Schwann Cell

TelodendriaAxon Terminal (Synaptic end

bulbs)

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Dendrite (trigger zone)

Cell Body

Axon

Unipolar Neuron

• All are sensory afferent• Cell bodies are located in the dorsal root

ganglia

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Cell Body

AxonDendrite (trigger zone)

Bipolar Neuron

• Location: special senses (smell, vision, hearing)

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Dendrites (trigger zone)

Cell Body

Axon

Multipolar Neuron

• Most common type of neuron• Interneurons and motor neurons

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Motor (Efferent) NeuronsEfferent = 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

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Sensory (Afferent) NeuronsAfferent = 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

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Association or Interneurons

• Neurons between the afferent and efferent neurons.

• Are only in the CNS

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Perineurium

Epineurium

Fascicle

Axon

Node of RanvierNeuronMyelin Sheath

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Glial Cells

• Associated with neurons• Provide Supportive scaffolding• Segregate and insulate neurons• Outnumber neurons by 10 to 1

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Supporting Cells in the CNS Astrocytes

• Star Shaped• Many functions

• Control the chemical environment around neurons by buffering K+ and NT

• Exchanges between capillaries and neurons (blood-brain barrier)

• Nutrient transfer

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Supporting Cells in the CNS Oligodendrocytes

• Oligodendrocytes produce the myelin sheath which provides the electrical insulation for some neurons in the CNS

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Supporting Cells in the CNSMicroglia

• Small oval cells with long thorny processes

• Monitor the health of neurons

• Specialized immune cells that phagocytize microorganisms and debris• Immune system cells

do not have access to CNS

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Supporting Cells in the PNS Schwann Cells

• Form the myelin sheath around axons in the PNS

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Schwann Cell

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The End