Lab Activity 12Histology of Nervous Tissue Martini Chapter 12Portland Community CollegeBI 2312Neuron3Myelin• 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 axon4Nodes of Ranvier• Areas between Schwann Cells that do not contain Myelin• Involved in saltatory conduction5Neuron Cell Body NucleusAxon HillockDendriteAxon6Myelin SheathAxonNode of RanvierSchwann CellTelodendriaAxon Terminal (Synaptic end bulbs)7Dendrite (trigger zone)Cell BodyAxonUnipolar Neuron• All are sensory afferent• Cell bodies are located in the dorsal root ganglia8Cell BodyAxonDendrite (trigger zone)Bipolar Neuron• Location: special senses (smell, vision, hearing)9Dendrites (trigger zone)Cell BodyAxonMultipolar Neuron• Most common type of neuron• Interneurons and motor neurons10Motor (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 side11Sensory (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 side12Association or Interneurons• Neurons between the afferent and efferent neurons.• Are only in the CNS13PerineuriumEpineuriumFascicleAxonNode of RanvierNeuronMyelin Sheath14Glial Cells• Associated with neurons• Provide Supportive scaffolding• Segregate and insulate neurons• Outnumber neurons by 10 to 115Supporting 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 transfer16Supporting Cells in the CNS Oligodendrocytes• Oligodendrocytes produce the myelin sheath which provides the electrical insulation for some neurons in the CNS17Supporting 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 CNS18Supporting Cells in the PNS Schwann Cells• Form the myelin sheath around axons in the PNS19Schwann Cell20The