{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Tissue ependymal cells cube shaped cells that produce

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: re brain surface & nonsynaptic Branched areas of gray matter areas • Extensions help form tight junctions btw neurons & Extensions endothelial cells of capillaries (bld-brain barrier) endothelial • Convert bld-glucose to lactate for nourishment, secrete Convert growth factors, regulate chemical composition, form scar tissue, etc. tissue, Ependymal cells= cube-shaped cells that produce CSF & help cube-shaped circulate it (via cilia) circulate Microglia= macrophages that wander CNS to phagocytize macrophages dead n.tissue, microorganisms, foreign matter dead • Help id sites of damage/infection since cluster in those areas Myelin Sheath Myelin Schwann cells= envelop fibers of PNS, winds around to form envelop myelin sheath; also helps in regeneration of damaged fibers myelin Satellite cells= surround cell bodies in ganglia (func unknown) Myelin= plasma membranes of glial cells (20% protein, 80% plasma lipids) form insulating sheath • Myelination of nervous system begins ~14th wk fetal Myelination system development, but not in brain @ birth development, • Process continues until late adolescence, but dietary fat Process needed most during early development needed • Oligodendrocytes (CNS) repeatedly wrap its p.membrane around adjacent fibers to form compact layers of myelin sheath sheath • Many oligodendrocytes are responsible for covering 1 axon • Schwann cells (PNS) spiral around a single fiber • Neurilemma= outer layer of sheath containing nucleus, cytoplasm outer Conduction Speed Conduction Basal lamina= surrounds myelin sheath; thin fibrous layer surrounds forms outermost layer (endoneurium) forms Nodes of Ranvier= gaps btw myelin segments • Internodes= myelinated seg’s Trigger zone= axon hillock + initial segment (btw a.h. & 1st glial cell); region important in initiating nerve impulse in Unmyelinated fibers occur in CNS & PNS; in PNS, schwann cells house 1-12 fibers & p.membrane folds over each once cells Conduction speed of nerve signal depends on 2 factors: • • • • Diameter of fiber & presence of myelin sheath Conduction occurs @ surface of fiber…more surface area .5-2 m/sec (unmyelinated) –vs- 3-15 m/sec...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online