Histology of the CNS Flashcards
how would you identify a neuron on a histological slide?
it has a cell body with a large nucleus with a well-developed nucleolus, and Nissl substance/bodies
What does it mean when it is said that dendritic spines are plastic?
they can either appear or regress if they are not being used
Where does the axon of a neuron appear from the cell body from?
the axon hillock
What does neuropil act as?
connective tissue for the neuron
What are the neurites that receive information and transmit it to the cell body are called what?
dendrites
the granular material that is present in the entire cell body and proximal part of the dendrites?
Nissl substance/ nissl bodies
Small projections that extend from the branches of the dendrites?
dendritic spines
What is the purpose of the dendritic spines?
they increase the receptive area
Where does the action potential originate at?
the axon hillock
What does the presynaptic terminal bouton contain?
mitochondria and synaptic vesicles containing NTs
what separates the pre- and post-synaptic membranes?
The synaptic cleft
What does the post synaptic cell membrane contain?
receptors for the NT and ion channels to initiate a new impulse
a synapse in which the postsynaptic membrane is on a dendrite of another neuron is called what?
axodendritic synapse
a synapse in which the postsynaptic membrane is on the cell body (soma) of another neuron is called what?
axosomatic synapse
A synapse in which the postsynaptic membrane is on the axon of another neuron is called what?
axoaxonic synapse
Where do electrical synapses occur?
at gap junctions
What do gap junctions contain that link pre- and post-synaptic membranes?
they contain connexon proteins
What are the supporting cells in the CNS called?
Glial cells
What are the proximal regions of astrocytes reinforced with?
intermediate filaments made of glial fibrillary acid protein (GFAP)
What is the hallmark marker for identifying astrocytes?
the glial fibrillary acid protein (GFAP)
What is the role of astrocytes?
support the neurons, establish the BBB, can remove NTs from the synaptic cleft
when astrocytes extend their processes and contact another structure what do they establish?
foot pads known as perivascular feet or perineural feet
what is the role of perineural feet?
helps astrocytes reuptake NTs
what is the role of the perivascular feet?
they block the pores that are found within the capillary beds that feed into the nervous system–> BBB
where are ependymal cells found?
lining the brain ventricles and central canal of the spinal cord
what type of cells are ependymal cells?
columnar or cuboidal cells
What is the role of ependymal cells?
facilitate the movement of CSF and likely involved in absorption
Where is the choroid plexus found?
in the roofs of the 3rd and 4th ventricle and parts of the lateral ventricular walls
What is the choroid plexus?
thin, well-vascularized pia mater covered by cuboidal ependymal cells
what contributes to the blood-CSF barrier?
tight junctions (zonula occludens) between epithelial cells
what is the role of microglia?
remove damaged or inactive synapses or other fibrous components; major mechanism of immune defense in the CNS
What do microglia originate from?
monocytes
what should you look for when trying to identify microglia histologically?
a simple elongated nuclei
What is the role of oligodendrocytes?
they extend processes that enwrap nearby axons in myelin
what do you look for when looking for oligodendrocytes histologically?
a very round and almost perfectly circular nuclei
What are the glial cells in the PNS?
neurolemmocytes (schwann cells) and satellite cells
What are neurolemmocytes and satellite cells derived from?
NCCs
What are the functions of neurolemmocytes?
myelinate peripheral nerves- providing electrical insulation
what are the functions of satellite cells?
provide structural and metabolic support for neuronal cell bodies
where are satellite cells found?
in dorsal root ganglions (DRG)
What is the outermost layer of the cerebral cortex?
the molecular layer
what is found in the molecular layer?
fibers and neuroglial cells
what is the 2nd layer of the cerebral cortex?
external granular later
what is the 3rd layer of the cerebral cortex?
external pyramidal layer
what is the 4th layer of the cerebral cortex?
inner granular layer
what is the 5th layer of the cerebral cortex?
ganglionic layer
what is found in the ganglionic layer?
extra-large pyramidal cells (Betz cells)
what is the 6th layer of the cerebral cortex?
multiform (polymorphic) layer
What is a clinical sign of alzheimer’s disease?
thinning of gyri- particularly those of the frontal and temporal lobes
what is identifiable histologically if a patient has alzheimer’s disease?
amyloid (amyloid B) plaques and neurofibullary tangles (tau protein)
what is the substantia nigra important for?
fine control of motor function
what do neurons in the substantia nigra contain?
numerous membrane bound granules of neuromelanin pigment
What does neuromelanin contain?
dopamine
what is the role of dopamine?
it has inhibitory effects in the brain in areas dedicated to movement
what are the distinctive inclusions seen in the remaining neurons in the substantia nigra called?
Lewy bodies
What are lewy bodies composed of?
aggregates of the protein alpha-synuclein and other proteins
How many layers make up the cerebellar cortex?
3
What is the first/ most superficial layer of the cerebellar cortex?
the molecular layer
what is located in the molecular layer of the cerebellar cortex?
neuropil and scattered neuronal cell bodies (basket cells)
what is the second layer of the cerebellar cortex?
purkinje cells
What is the third layer/ deepest layer of the cerebellar cortex?
granular layer
what is located deepest in the cerebellar cortex?
the cerebellar medulla
where does the central canal of the spinal cord lie?
in the central commissure of the gray matter
what is found immediately around the neurolemmocytes and consists of reticular fibers, fibroblasts, and capillaries?
endoneurium
what enwraps the fasicles of axons, neurolemmocytes, and endoneurium?
perineurium
what is a dense irregular fibrous coat in between fasicles and surrounding the peripheral nerve?
epinerium
what are neurofibrillary tangles formed by?
an abnormal accumulation of tau
