[2] Lecture 19: Nervous Tissue II Flashcards
(50 cards)
Non-neuronal cells typically derived from embryonic neural crest tissue
Glial cells
Serve in various support functions in the PNS and especially in the CNS
Capable of cell division under appropriate conditions
Glial cells
Types of glial cells:
Astrocytes Oligodendrocytes Schwann cells Microglial cells Ependymal cells
“Glia” =
Glue
Glial cells hold systems together
Derived from neural crest (neuroepithelium)
Found only in CNS
Have numerous processes w/ expanded feet (pediceles) that terminate on capillaries or pia matter
Astrocytes
found predominantly in white matter
Have long processes w/ few branches
Fibrous astrocytes
Found in predominantly GRAY matter
Have shorter processes w/ many short branches
Protoplasmic astrocytes
Functions of astrocytes
- Regulate composition of intercellular environment or entry of substances into
- Structural support
- Blood-brain barrier - mediate exchange of nutrients btw blood and neurons
- development of cerebral cortex
- K+ sink
- secretion of neuron trophic factors
- uptake/metabolism of neurotransmitters
- help form noncollagenous scar tissue after injury to CNS
Glia limitans
End feet of astrocyte
-Derived from neural crest (neuroepithelium)
-Found only in CNS
Function: closely asso. W/ neuron cell bodies in GRAY matter and function as satellite cells;
-Surround axons of unmyelinated fibers in GRAY matter-like schwann cells
*Myelinate schwann cells in CNS
[one cell can myelinated multiple axons]
Oligodendrocytes
Derived from neural crest
Functions:
Myelinated axons in PNS
Each one myelinated a section of a single axon
Schwann cells
Derived from MACROPHAGE precursors (bone marrow)
Function as phagocytic in PNS;
Recruit leukocytes across blood brain barrier;
Modulate development of immune processes along with astrocytes
Microglial cells
- Ciliated cuboidal cells
- derived from neuroepithelium and line ventricular system of CNS [brain]
- function in transport-fluid
- in choroid plexus may be principal cell type that secretes CSF
Expendymal cells
Derived from neural crest
Form moons (crescents) around cell bodies in ganglia
Function as insulators
Satellite cells
Schwann cell plasma membrane wraps around axon
Schwann cell sytoplasm is squeezed out, leaving behind concentric layers of membranes
Myelination in PNS
Outer and innermost points of fusion btw the outer leaflets and inner leaflets [extracellular leaflets]
Internal and external mesaxon
Electron-dense line created by extracellular space btw adjacent outer leaflets
Major protein is a transmembrane protein that forms homodimers
Intraperiod line
Found only in PNS
Homodimers form homotetramers w/ opposing outer leaflets
Functions to hold leaflets together
Intraperiod line
Electron-dense line created by cytoplasmic space remnant btw adjacent inner leaflets
Myelin basic protein [also found in PNS] is an abundant protein asso. W/ inner leaflets
Function: stabilize lipids in the leaflet;
There are a number of forms created by splicing of a single gene
Major dense line
Residual areas of cytoplasm w/ in the major dense lines
Schmidt-lanterman clefts [incisures]
Compare cytoplasmic-axon contacts in PNS and CNS
Note contact by astrocyte end-foot in node of ranvier in CNS
Note role of tight junctions and connexin 32 in PNS nodes
Compare autotypic and heterotypic junctions
Oligodendrocytes / nodes of ranvier
Figure to know:
Fig 8-10 and fig 8-12
Voltage gated Ca+ channels
SNAPs bind synaptic vesicles to presynaptic membrane
Vesicle docking proteins
Synapsins
Presynaptic membrane
Soluble NSF (N-ethylmaleimide-sensitive fusion proteins)- helps w/ binding process
Found in cytosol of terminal
Allow exocytotic vesicle to snap together or combine to membrane
SNAPs
