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66 Cards in this Set

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  • Back
What does Glia mean?
What is the general function of Glial cells?
How do Glia relate to neurons in terms of number and CNS volume?
-Outnumber Neurons 10:1
-But occupy only 50% volume b/c Neurons are so much larger
How do Glia compare to Neurons in terms of cytology?
-Do Have processes
-Do Not Have Synpases or AP
What ability do Glial cells have that Neurons do not have?
Mitotic ability in adult life
What is Gliosis?
A Glial scar made by a glial cell repairing a CNS lesion
What is a bad effect of Glial repair of CNS lesions?
CNS cancer - most is of glial origin.
List 5 different types of Glial cells:
1. Astrocytes
2. Oligodendrocyte
3. Schwann cells
4. Microglia
5. Ependymal cells
What are Astrocytes?
The Largest, Most Numerous Glia
What do Astrocytes look like?
Star-shaped with many long processes.
2 Types of Astrocytes:
Difference between fibrous and protoplasmic astrocytes:
Fibrous = long thin processes found in white matter.
Protoplasmic = Short/thick processes, found in gray matter.
What is the functional part of astrocytes?
Their END FEET - foot processes that contact nerves where they are unprotected by myelin.
-Also contact/surround blood vessels, and line ventricles.
What are 5 functions of Astrocytes?
1. Support and repair
2. K+ spatial buffering
3. NT removal
4. Nutrition of neurons
5. NT receptors
How do astrocytes Support and Repair the CNS?
Support: fill spaces not occupied by neurons/bld vessels
Repair: proliferate after CNS damage to form glial scars.
How specifically do Astrocytes fill the spaces in the CNS?
By GFAP - glial fibrillary acidic protein - which forms the Connective tissue of the CNS.
What is K+ spatial buffering and how do Astrocytes do it?
Removal of K+ from spiking neurons so neuronal membrane potential is maintained - astrocytes have K+ channels.
What does K+ uptake by astrocytes do to the cells?
Causes Vm to change, but they are NOT excitable.
How do Astrocytes achieve NT removal?
By taking up NT from synaptic clefts to terminate the signal.
What is the function of Oligodendrocytes?
Myelination of axons in the CNS
How does myelination by oligodendrocytes differ from schwann cells?
Schwann cells only myelinate one axon; Oligodendrocytes can myelinate multiple axons.
What are MAG and NI-35, and what do they do?
Myelin-associated Glycoprotein
Neurite inhibitor
-Inhibit regeneration of CNS axons.
What are Schwann cells and what is their function?
The PNS counterpart of Oligos
-Function to myelinate axons in PNS.
What is the main feature of Schwann cells compared to Oligo?
Only myelinate ONE axon; one axon typically has up to 500 schwann cells wrapped around it.
Do Schwann cells ALWAYS only associate with one axon?
No; if the axon is unmyelinated, then the Schwann cell can wrap more than one axon.
What are Microglia and what is their function?
Small oval cell bodies with many short processes.
-Function in phagocytosis of CNS debris
What cell do Microglia act like?
What are Ependymal cells?
Cuboidal or Columnar epithelial cells lining the inside of the neural tube.
What feature allows ependymal cells to function?
Presence of cilia or microvilli - beats on CSF causing it to circulate
What joins ependymal cells at their basal edge?
Desmosomal junctions - they allow some CSF to penetrate between them.
What is a mesaxon?
Fusion of the myelin sheath as it wraps around an axon.
What mesaxon is present in the CNS?
Only an inner - because oligodendrocytes do not form an outer mesaxon.
What mesaxon is present in the PNS?
Both inner and outer mesaxons - because Schwann cells wrap around so many times.
What is Myelin basic protein?
A protein in both PNS and CNS myelin - on the major dense line
-high in lipid content
What are Major Dense lines?
Apposed cytoplasmic faces
What are Minor dense lines?
Apposed extracellular faces
What determines the thickness of myelin sheath?
The axon size - larger = thicker
What are nodes of ranvier?
Membrane sites where exposed to ECF - in PNS covered by schwan cytoplasm; in CNS bare.
What allows for saltatory conduction?
High content of fast sodium channels at the nodes
What will always occur at the node of ranvier if it occurs at all?
Branching of an axon
What are Clefts of Schmidt-Lanterman?
Splits between Major Dense lines - filled with cytoplasm; function to give nutrition to the inner leaflet.
Where are clefts of schmit lantermen found?
ONLY IN PNS - because only schwann cells have inner leaflets that are so far away they need special nutrients.
How fast does myelination increase conduction?
Up to 120 m/sec (as opposed to <2 m/sec if unmyelinated)
2 diseases of myelination:
-Multiple Sclerosis
-Guillian Barre syndrome
Features of MS:
-Demylination of CNS axons
-Both sensory/motor axons
Symptoms of MS:
-Disrupted BBB
What is Guillian Barre?
Autoimmune disease against one's own myelin
Nerves affected in Guillian barre:
Peripheral nerves to muscle/skin
Where is connective tissue found in the brain?
ONLY in association with blood vessels - collagen.
What is the basal lamina that surrounds the CNS?
Pia mater
What is the BBB?
The endothelial lining that protects the brain
How are the endothelial cells of the BBB connected?
Via TIGHT JUNCTION - with high electrical resistance.
What is the Oersteiner-REdlich zone?
Interface of the PNS and CNS
Is the sensory ganglion in the dorsal root part of the PNS or CNS?
PNS; the obersteiner redlich zone is thus proximal to the dorsal root ganglia
What are the 2 types of ganglia in the PNS?
1. Craniospinal ganglia
2. Autonomic ganglia
What are Craniospinal ganglia?
-Dorsal root ganglia
-Cranial nerve sensory ganglia
What types of neurons are in the craniospinal ganglia?
Pseudounipolar with NO DENDRITES
What are the supportive cells that surround the pseudounipolar neurons of craniospinal ganglia?
Satellite cells - similar to schwann cells but of neural crest origin.
What neuron type is in Autonomic ganglia?
What is Vasa nervorum?
The connective tissue and blood vessels that surround and supply PERIPHERAL nerves
What is a nerve fiber?
An axon plus its schwann cell sheath.
What can peripheral nerves contain?
Both myelinated and unmyelinated and both motor and sensory fibers.
What are the 3 layers of connective tissue around a peripheral nerve?
1. Endoneurium
2. Perineurium
3. Epineurium
Surrounds all nerve fibers
Collagen + Reticular fibers
Flat epithelial-like layer
-Surrounds fascicles
Surrounds an entire nerve consisting of many fascicles