Lab Activity 12 Histology of Nervous Tissue Martini

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

Neuron 2

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 3

Nodes of Ranvier • • Areas between Schwann Cells that do not contain Myelin Involved in saltatory conduction 4

Dendrit e Nucleus Neuron Cell Body Axon Hillock Axon 5

Schwann Cell Axon Myelin Sheath Node of Ranvier Telodendria Axon Terminal (Synaptic end bulbs) 6

Unipolar Neuron Dendrite (trigger zone) Cell Body • • Axon All are sensory afferent Cell bodies are located in the dorsal root ganglia 7

Bipolar Neuron Dendrite (trigger zone) • Cell Body Axon Location: special senses (smell, vision, hearing) 8

Multipolar Neuron Cell Body Axon Dendrites (trigger zone) • • Most common type of neuron Interneurons and motor neurons 9

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 10

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 11

Association or Interneurons • • Neurons between the afferent and efferent neurons. Are only in the CNS 12

Neuron Fascicle Axon Myelin Sheath Node of Ranvier Perineurium Epineurium 13

Glial Cells • • Associated with neurons Provide Supportive scaffolding Segregate and insulate neurons Outnumber neurons by 10 to 1 14

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 15

Supporting Cells in the CNS Oligodendrocytes • Oligodendrocytes produce the myelin sheath which provides the electrical insulation for some neurons in the CNS 16

Supporting Cells in the CNS Microglia • • • 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 17

Supporting Cells in the PNS Schwann Cells • Form the myelin sheath around axons in the PNS 18

Schwann Cell 19

The End 20