Histology of the CNS Flashcards
How does a nerve signal travel through the nerve?
from dendrite –> cell body –> axon
What are dendritic spines?
processes on dendrites increase surface area so it is more receptive to signals
What is nissl substance?
large, basophilic masses of free polysomes and RER in cell bodies of neurons
What is the terminal arborization?
distal end of the axon some have branching, collateral branches
What are telodendria?
dilation of axon branch ends
contact postsynaptic cleft
What is the most common type of neuron found throughout CNS? What does it look like?
multipolar
many dendrites, one long axon
What does a unipolar neuron look like? Where is it found?
cell body w/ single short process w/ one main axon peripheral process to dendrites central process to end of axon sensory = dorsal root ganglia and cranial ganglia
Where are bipolar neurons found and what do they look like?
one long dendrite w/ one long axon
sensory neurons of retina, olfactory mucosa, and inner ear
What do anaxonic neurons look like and where are they found?
lack true axons and do not produce action potentials, but regulate local electrical changes of adjacent neurons
just a bunch of dendrites around cell body
What type of neurons compromize 99% of all neurons in adults?
interneurons = btw other neurons
What is contained in the presynaptic terminal bouton?
mitochondria
synaptic vesicles
What is contained in the postsynaptic cell membrane?
receptors for the NT
ion channels to initiate a new impulse
How does an electrical synapse work?
current flow occurs via gap junctions = link pre and postsynaptic membrnes
*gap jxns contain connexon proteins
What do astrocytes do?
help form BBB
regulate interstitial fluid composition
structural support and organization to CNS
asst in neuron dev
replicate to occupy space of dying neurons
What is neuropil?
fibrous intercellular network of cellular processes emerging from neurons and glial cells
What do the perineural feet of astrocytes do?
clean debri
NT recycling
What are glial fibrillary acid proteins?
reinforce intermediate filaments of proximal regions of astrocyte processes
What are oligodendrocytes?
myelinate neuronal axons in cns
extend many processes that wrap around portion of a nearby axon
can wrap multiple neurons
*given axon covered by many oligodendrocytes
When do oligodendrocytes work?
When do schwann cells work?
oligo: 6th months –> puberty
schwann: 4th month
What cells myelinate axons in the PNS?
What are they derived from?
Schwann cells
NCC derived
myelinate motor roots before sensory
What are ependymal cells?
columnar or cuboidal cells that line ventricles and central canal
apical end may have cilia and microvilli
facilitate mvt of CSF
joined by apical jxnal complexes
*no basal lamina
Where is the choroid plexus found?
roofs of 3rd and 4th ventricles and parts of lateral ventrical walls
What do microglia do?
phagocytic cells from monocytes
migrate to remove damaged/inactive synapses or other fibrous things
less numerous than oligodendrocytes or astrocytes
What is grey and white in the spinal cord?
grey in center = ventral, dorsal, lateral horns
white mater in periphery: sensory and motor tracts
Where is the central canal?
lies in central commissure of grey matter
lined by ependymal cells
What are the 3 layers of the cerebellar cortex?
molecular layer = outer, light staining; mostly neuropil w/ scattered cell bodies
purkinje cells = at border btw molecular and granular layers
granular layer = dark, central, small, densely packed neurons
What type of tissue makes up the cerebellar medulla?
white matter
What is the substantia nigra?
large mass of grey matter extending throughout midbrain
divides cerebral peduncles into dorsal and ventral parts
neurons are multipolar
numerous neuromelanin granules
contain dopamine
What are the 6 layers of the cerebral cortex?
- Plexiform (neuroglia and horizontal cells of cajal)
- Small pyramidal cell layer
- layer of medium pyramidal cells
- Granular layer
- large pyramidal cell layer (motor)
- polymorphic layer
What is neocortex?
new layers of brain
archicortex = old
What are the 3 layers of the hippocampus?
polymorphic layer: nerve fibers and small cell inerneurons
middle pyramidal cell layer
molecular layer: dendrites of pyramidal cells
What are the 3 layers of the dentate gyrus?
polymorphic layer: nerve fibers and cell bodies of interneurons
middle granule cell layer: round, neuronal cell bodies of dentate granule cells
molecular layer containing dentrites of granule cells
What is the hilus?
area where the head of the hippocampus abuts the dentate gyrus
multipolar neurons here = mossy cells
receive input from mossy fibers of granule cells of dentate gyrus –> relay signals back to other cells in dentate
What occurs histologically in alzheimer’s?
striking thinning of gyri, esp frontal and temporal lobes
amyloid beta plaques in cortex
neurofibrillary tangles= accumulation of tau
