Histo of CNS Flashcards
Typical neuron cell body
- large nucleus w a well developed nucleolus & nissl substance
- numerous dendrites and long axon emerges from axon hillock
Neuropil is:
dense network of nerve fibers & their branches & synapses, together with glial filaments
Anterograde transport
carries material from the nerve cell body to axon. Kinesin-MT motor protein
Retrograde transport
carries material from axon terminal to cell body or dendrites. utilizes dynein
Slow axonal transport
speed 0.2-4 mm/day. Anterograde movement typically cytoskeletal elements
Fast axonal transport
20-400 mm/day, bidirectional movement of organelles. retrograde may include endocytosed toxins and viruses
Synaptic communication is uni or bidirectional?
unidirectional
In a chemical synapse presynaptic terminal bouton contains what?
lots of mitochondria and synaptic vesicles with NT released by exocytosis
separating the pre and postsynaptic membrane is
synaptic cleft 20-30 nm wide
Postsynaptic cell membrane includes what?
receptors for NT and Ion channels to initiate new impulse
Astrocytes form
a vast network of delicate terminals contacting synapses and other structures. Terminal processes of a single astrocyte associate with 1M synaptic sites
Proximal regions of astrocytes are reinforced with what intermediate filament?
glial fibrillary acid protein (GFAP)
Oligodendrocytes
Extend processes that enwrap nearby axons in myelin, will enrap axons from multiple neurons and a single axon can be wrapped by multiple oligo’s
Oligodendrocytes on a histo slide
usually appear as small cells with rounded condensed nuclei and unstained cytoplasm.
Ependymal cells
columnar or cuboidal cells that line the brain ventricles and central canal of SC
Apical end of ependymal cells
may have cilia and long microvilli, facilitate movement of CSF, involved in absorption
Ependymal cells are joined…
apically by apical junctional complexes. no basal lamina present.
Choroid plexus is found where
roofs of 3rd and 4th ventricles and parts of lateral ventricle walls.
Choroid plexus is composed of…
thin, elaborated folded layer of well-vascularized pia mater covered by cuboidal ependymal cells.
Action of choroid plexus is to
remove H2O from blood and release it as CSF.
Microglia
major mechanism of immune defense in the CNS, originate from monocytes
Astrocyte function (5)
- BBB barrier
- Regulates interstitial fluid comp
- structural and organization to CNS
- Assists neuronal development
- Replicates to occupy space of dying neurons
Oligodendrocyte function
- myelinates and insulates CNS axons
2. Allows faster action potential
Ependymal cell function:
- lines ventricles of brain and central canal of SC
2. assist in production and circulation of CSF
Function of microglial cells
- phagocytic cells that move through CNS
2. Protects CNS by engulfing infectious agents and other potential harmful substances
Molecular layer of cerebellum:
has much neuropil and scattered neuronal cell bodies
Purkinje cells layer of cerebellum
extend dendrites t/o molecular layer as a branching basket of nerve fibers-conspicuous in HE stain sections.
Granular layer cerebellum
contains various very small densely packed neurons and little neuropil
The cerebral cortex is divided into old and new called
Archicortex-3 layers
neocortex- 6 layers
90% of cortex is neocortex
Neocortex has cells divided into 5 categories
- pyramidal
- granule (stellate)
- Cells of martinotti
- Fusiform
- horizontal cells of cajal
* all cortex contains supporting glia as well
Pyramidal cells
pyramid shaped cells with apex directed towards cortical surface. Huge UMN of the motor cortex (betz) are the largest of these cells
Granule (Stellate) cells
small neurons with a cell body in the shape of a star
Cells of martinotti
small polygonal cells with a few short dendrites
Fusiform cells
spindle shaped cells oriented at right angles to the surface of cerebral cortex
Horizontal cells of Cajal
small and spindle shaped but oriented parallel to the surface (least common)
6 cortical layers
- Molecular
- External granular
- External Pyramidal
- Inner Granular
- ganglionic (internal pyramidal)
- Multiform (polymorphic)
Molecular cortical layer:
consists largely of fibers, most of which travel parallel to surface & mostly neuroglial cells and horizontal cells of cajal
External granular cortical layer:
consists mainly of small pyramidal cells and granule cells
External pyramidal cortical layer:
pyramidal cells are larger and pyramid shape, not sharply demarcated from layer 2
Inner granular cortical layer:
many small granule cells
Ganglionic cortical layer:
very large pyramidal cells (betz) motor areas
Multiform (polymorphic) cortical layer:
cells of diverse shape, many are fusiform cells
Alzheimer’s
memory failure progressing to motor skills, speech, sensation-most common
thinning of gyri esp in frontal and temporal lobes
Alzheimer’s histo
amyloid b plaques: amorphous, pink masses in cortex
neurofibrillary tangles- flame shaped skeins formed by abnormal accumulation of tau
