Nervous System

Question 1

Ependymal Cells

Answer 1

• Support cell in CNS
• Arises from neuroepithelium
• Line ventricles of brain and spinal cord
• Simple cuboidal/columnar cells held together by adhering junctions; some have cilia to circulate CSF
• Only see tight junctions when ependymal cells form choroid plexus, a structure close to capillary that produces CSF

Question 2

Microglia

Answer 2

• Support cell of CNS
• Arise from macrophages, not CNS
• Smallest glia
• Phagocytic: eliminate non-viable neurons and glial cells during development; eliminate damaged/dying neurons and inactive synapses in adults
• Produce molecules to recruit leukocytes across blood-brain barrier for brain immune response

Question 3

Astrocytes

Answer 3

• Support cells of CNS
• Arise from neuroepithelium
• Structural support, lying between neurons and capillaries, sending processes to basement membrane of capillaries
• Made of glial fibrillary acidic protein (GFAP), the monomers of glial filaments (intermediate filaments)
• K+ sinks; found at nodes of Ranvier
• Linked by gap junctions to allow passage of small materials
• Can accumulate leftover NT to stop synaptic transmission because have NT receptors
• NT affect astrocyte function by changing permeability of ion channels, ability to uptake NT, morphology, and neurotrophic factors released
• Release factors that affect tight junctions of endothelial cells of capillaries to control permeability of blood brain barrier; these factors regulate blood flow in brain capillaries
• Phagocytic

Question 4

Oligodendrocyte

Answer 4

• Support cell of CNS
• Arise from neuroepithelium
• Myelinate cells of CNS from initial segment to axon terminal
• One oligodendrocyte sends out 40-50 processes; therefore, if lose one oligodendrocyte, lose a lot of myelinating potential

Question 5

Schwann Cells

Answer 5

• Support cells of PNS
• Surround all PNS neurons
• Produce growth factors at lesions to encourage sprouting along CT coats
• Phagocytic at lesion sites
• Myelinate
• One Schwann cell makes one internode (so losing one Schwann cell is not devastating)
• Surrounded by connective tissue coats (endo-, peri-, and epineurium

Question 6

Satellite Cells

Answer 6

• Support cells of PNS

- Surround cell bodies