What are the Cellular elements of the IMMature Nervous System?

• Primitive, Pluripotential Neuroectodermal cells
• Embryonal Tumors

Neurons, Glia (Astrocytes, Oligodendroglia, Microglia)

Ependymal Cells 

Centrum Semiovale

Large area of central, white matter subjacent to the cortex 

What is the origin of the Neuron? 

Neuroectodermal 

Pyramidal Neuron

Found in cerebral cortex, triangular, apex pointing toward surface, base downward,  myelinated axon arises from base to white matter

Cortical Dysplasia

Nissl Material

Characteristic of neurons. Consists of rosettes of polysomes and RER; has roles in protein synthesis. Found in nerve CELL BODY (perikaryon) and dendrites NOT axon hillock or axon. 

How is the Nissl material distributed in Motor Neurons?

Coarse clumps and is called Nissl bodies. 

How is the Nissl material distributed in Sensory Neurons? 

Evenly within the cytoplasm and is designated as Nissl substance. 

Heavy Metal Stains

Ionic solutions of silver and gold used to illustrate elongated cytoplasmic processes. 

Efferent limb of the Neuron

Single Axon: impulse destined to synapse with other neurons 

Afferent Limb of neurons

Dendrites: receive impulses from the axons to other neurons

Facilitation

Sum Total  of  + presynaptic impulses converging on 2 or 3 neurons from other primary neuronal sources, promoting discharge of an electrical impulse or firing. 

Inhibition

Sum total of (-) presynaptic impulses converging on a 2 or 3 order neuron, PREVENTING discharge or firing 

Summation

Sum Total of pre-synaptic + and - impulses converging on a 2 or 3 order neuron; if sum total is +, then will fire and vice versa. 

Final Common Pathway 

Convergence of several facilitating and inhibiting presynaptic impulses from multiple neuronal sources upon 2 or 3 neuron, determining whether or not the neuron will fire

Are neurons continuous or a syncytium?

Continuous

Acute Neuronal Injury 

Variant of Coagulation Necrosis; shrinkage of the neuron (pyknosis), irreversible injury, NOT visible until 12+ hrs of post injury

DEAD RED NEURON

• entire cell shrinks (pyknosis)
• cytoplasm become brick-red discoloration
• nucleus shrinks and loses its cellular detail 
• neuron does not regenerate (post-mitotic)

Neurophagia

When macrophages engulf and ingest dead-red neuron. Also referred as Glial Nodule (esp. for viral and Rickettsial infections). 

Ferruginization or 'mummification'

Injury to the CNS of a fetus or infant. Dead neurons are coated with mixture of calcium, protein & iron (mineralization). 

This process is also termed ferruginization or mummification; not removed by immature macrophages. 

Parasagittal Region

In cerebral cortex, 1" lateral to sagittal fissure, border zone between anterior and middle cerebral artery

Hippocampal Region

border zone of middle and posterior cerebral arteries. 

Equator of the Cerebellar Convexity 

Equator of the cerebellar convexity between the superior and inferior cerebellar arteries. 

Pathoclisis 

Axonal Reaction

Swelling of neurons and poss. Reversible

Axon damage --> retrograde response of 1st neuron: nissl material disperse and invisible to microscope

Central Chromatolysis 

Loss of nissl material in the central area of cytoplasm in Axonal rxn. 

(more info pending) 

Trans-synaptic Degeneration 

Neuronal swelling and poss. REversible 

Injury occurs to the axon of pre-synaptic, 1st order neuron and post-synaptic neuron swells.

Hypertrophy of the Olive

Ex. of trans-synaptic degeneration: many pre-synaptic neurons to inferior olivary nucleus are injured --> post-synaptic neurons swell --> diffuse enlargement of the entire structure. 

Lipofuscin Granules 

Neuromelanin

Normal intracytoplasmic neuronal pigment found in specific nuclei. Not related to melanin pigment of the skin and lost in pigmented nuclei in Parkinson's Disease. 

Cowdry Type A intraNuclear Inclusions

Large, reddish-purple (magenta) intranuclear inclusions which displace the chromatin to the nuclear margin. 

Ganglioglioma

"Ganglion Cell Tumor": neoplasm containing neurons 

Astrocyte 

• neuroectodermal origin
• contain Glial Fibrillary Acid Protein (GFAP): which is a marker for astrocytes 
• have cytoplasmic processes radiating from body, giving star app. and forming neuropil, in which neurons are embedded

Protoplasmic Astrocytes 

• located in Gray matter
• plump cell body
• thick cytoplasmic processes

Fibrillary Astrocytes 

• located in White matter
• Spindled cell bodies
• Thin, delicate cytoplasmic processes

Gliosis 

• non-specific rxn to injury
• nucleus is eccentric and NO nucleolus
• protoplasmic astrocyte reacts acutely
• fibrillary astrocyte reacts in chronic mode

Bergmann's Gliosis

Injury to the cerebellum results in activation of astrocytes within the plane of Purkinje cells 

Alzheimer type II 

liver disease --> high ammonia levels --> nucleus swells 2-3x, loses chromatin and becomes watery clear

(also seen in Wilson's disease) 

Rosenthal Fibers

A sign of non-specific rxn. to injury; intracellular and representing swollen astrocyte processes filled w/ glial filaments 

Corpora Amylacea 

(Amyloid bodies)

• round, gray-blue structures w/ concentric rings, which increase in proportion to age.
• found in pial & subependymal & around blood vessels
• Contain polyglycosan
• found in LaFora's disease: systemic storage disease

Oligodendroglia 

Myelin-forming cells of the CNS.

How does an oligodendroglia cell show on H&E stain? 

• nucleus looks like a lymphocyte: small, round and dark
• nucleus w/ halo --> 'fried egg' appearance
• 3-5 oligo... cells can surround cell body of neuron --> benign satelitosis 

Multiple System Atrophy

• Associated with Glial cytoplasmic inclusions (GCI) 
• Sporadic olivopontocerebellar atrophy
• Striatonigral degeneration
• Shy-Drager Syndrome (Familial Dysautonomia) 

Microglia 

• Mesodermal Origin 
• Arise from monocytes & fxn. as the scavenger cells (phagocytes) of the CNS. 

How does the nervous system heal? 

By cavitation!!! 

Rod Cells 

They form when spindled microglial nuclei become prominent in response to injury 

Glial Nodules

focal constellation of neuronal ingestion

esp. for viral dzs

Ependymal Cells 

• line the central canal and ventricles, & luminal surface of choroid plexus, produce CSF
• neuroectodermal origin
• GFAP + cytoplasmic processes
• blepharoplast: remnant of cilia, which disappears after birth

Hydrocephalic Edema

Tight ependymal junctions are opened and CSF leaks into adjacent parenchyma 

normally ependymal have tight jxnions that are impermeable to the CSF --> barrier fxn.