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