Nervous Tissue - Neuroglial Cells Flashcards
What are the functions of neuroglia?
-Monitoring synapses
-Regulating the flow of CSF
-Scavenging neurotransmitters
-Releasing gliotransmitter e.g glutamate
What are the neuroglia of the CNS vs PNS
CNS
-Astrocytes
-Oligodendrocytes
-Microglia
-Ependymal cells
PNS
-Schwann cells
What are astrocytes, what do they do and what are the 2 types?
-Provide structural and metabolic support to neurons
-Largest neuroglial cell
-i) Protoplasmic astrocytes (grey matter of CNS)
-ii) Fibrous astrocytes (white matter of CNS) - assist in maintaining the blood-brain-barrier
Has intermediate filaments formed by protein glialfibrillary acidic protein (GFAP)
What are Oligodendrocytes, what is their function and what are the 2 types?
-Function in electrical insulation and in myelin production in the CNS
-Smaller and fewer processes than astrocytes
-Located in grey and white matter of CNS
-Small nucleus, ER, free ribosomes, mitochondria, golgi
-Types: Intrafascicular oligodendrocytes, Satellite oligodendrocytes
What are Intrafascicular Oligodendrocytes?
-Located in rows beside bundles of axons
-Manufacture and mainatin myelin on axons of CNS
-Single oligodendrocyte forms a number of processes
-Wraps around small region - internode
What are satellite oligodendrocytes?
-Closely applied to cell bodies of large neurons
-Present only in grey matter
-Function not clearly understood
What are Microglial cells?
-Members of the mononuclear phagocyte system - func as phagocytes - clear debris and damaged structures within CNS and protect NS
-Small, dark staining cells
-Little cytoplasm, oval to triangular nucleus and irregular short processes
-Activated microglia secrete interferon gamma- this activates more microglia and attracts T-lymphocytes
What is the best stain to use to see microglial cellsß
Immunohistochemical staining
What are Ependymal cells?
-Low columnar epithelial cells
-Line the ventricles of the brain and spinal cord
-Lots of mitochondria and bundles of intermediate filaments
-Can be ciliated
-Facilitates movement of CSF
-Dont rest on basement membrane
What are Schwann cells
-PNS neuroglial cells
-myelinated and unmyelinated coverings over axons in PNS
-Myelin is the plasmalemma of the schwann cells organised in concentric rings around the axon
-Nodes of Ranvier - interruptions in myelin sheath
-Permit salutatory conduction - impulse transmission
What are bundles of nerve fibres called?
Fascicles
What are the 3 layers of connective tissues found in peripheral nerves?
- Epineurium - outermost layer - dense irregular collagenous connective tissue - thick elastic fibres
- Perineurium - middle layer
- Endoneurium - innermost layer - loose connective tissue - thinner - surrounds individual nerve fibres - in contact w basal lamina of schwann cells
