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Nervous tissue Nervous system Nervous tissue • Cellularity : – neurons – supporting cells – different in CNS and PNS • Extracellular matrix – GAGs and PG – No fibrils (e.g. collagen) • Neurons – soma – processes • Dendrites • Axon – Axon hillock – Terminal arborization – Sinaptic buttons The neuron • Nucleus: centrally , euchromatic with visible nucleolus • Basophilic granules = Nissl bodies – RER and ribosomes – Only in perykarion • Neurofilaments and microtubule visible in silver staining – In both perykarion and processes • Lipophuscin Methods of study in OM • H&E staining – Form of perykarion – Little information about axon • Silver staining – good observation of processes • Toluidine blue – highlights the Nissl bodies What can we see on a nervous tissue slide? Neurons Glial cells Embedded in extracellular matrix www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame6.html Cerebral cortex HE 60x Spinal cord Nissl stain 250X cytochemistry.net Cerebral cortex Silver stain Types of neurons • Shape of cell body: pyramidal, star- shaped, granular • Size – large > 100μm, – small 10 μm • No. of processes – unipolar – bipolar – multipolar Neurons classification Unipolar neuron Bipolar neuron Anterior horn spinal cord Nissl stain Purkinje cells, cerebellum, silver stain Multipolar neuron www.sciencephoto.com Supporting Cells: Neuroglia • Provide a supportive scaffold for neurons • Segregate and insulate neurons • Produce chemicals that guide young neurons to the proper connections • Promote health and growth Supporting Cells: Neuroglia Neuroglia in the CNS Neuroglia in the PNS Astrocytes Satellite Cells Microglia Schwann Cells Ependymal Cells Oligodendrocytes Oligodendrocytes • Found in both white and gray matter • Form myelin sheath of axons in CNS • Small round, nuclei, with processes surrounding several axons • Majority of CNS cellularity GLIAL CELLS IN CORTEX http://www.encorbio.com Cerebral cortex HE 60x academics.eckerd.edu Astrocytes in culture- in red: fluorescently marked glial fibrillary protein Astrocytes • Star-shaped with many processes • Link between neurons and capillaries • Two types: – protoplasmatic: mostly in gray matter, numerous processes, short and ramified – fibrous: mostly in white matter, fewer processes and longer Silver stainig astrocytes Various glia in human cortex, H&E Microglia • In both white and gray matter • Small, elongated cells • Short, irregular processes Schwann cells • Form myelin sheath in PNS • Several Schwann cells/ 1 axon Myelinated axons and Schwann cells cal.vet.upenn.edu 1 –axon 2 – endoneurium 3- myelin sheeth 4- Schwann cells HE 250x Satellite cells • In PNS • Small cells surrounding neuronal bodies in ganglia Neuropil Neuropil • It refers mainly to the gray matter between cell bodies. • With conventional stains, this area is not stained • Other preparations demonstrate the numerous neuronal and glial cell processes that compose the neuropil. Neuropil http://courseweb.edteched.uottawa.ca/medicine-histology/English/SS_BasicTissues/ Nervous_Tissue.html
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