Neurocytology --review from M1 Flashcards
PNS (compsition)
cranial nerves and spinal nerves
groups of neurons cluster in ganglion
CNS (composition)
Brain and spinal cord
groups of neurons cluster into nuclei or form sheets of nuclei ( cortices)
Who are the glial cells in the PNS
satellite cells and schwann cells
who are the glial cells in the CNS
oligodendrocytes, astrocytes, ependymal cells, and microglia
What layer of cells (embryo) does the neural tube form from?
Ectoderm
Where (layer in embryo) do the neural crest cells come from?
Ectoderm
Neural crest cells can derive into what types of structures/ cells?
Peripheral Neurons Schwann cells Satellite Cells Adrenal Medulla (Chromaffin cells) Meningeal coats-- pia mater and arachnoid Melanocytes Facial cartilage
What does the Neural tube develop into?
Brain and spinal cord
What cells compose neural tube? What do these cells give rise to?
epithelium with cilia
Neurons and glia of the CNS
Function of Glia cells of CNS?
provide guidance (via production of a substrate) to migrating neurons and growth factor support
Multipolar cells
many branches off of soma.
found in large motor neurons
Part of autonomic nervous system and integrated neurons (lie within brain and spinal cord)
Pseudounipolar neuron
sensory neurons
Two parts that extend from cell body have joined. They have bypassed the cell body
Dendritic spines
on dendrites
respond to excitatory or inhibitory input.
Very plastic system
- when they don’t have excitatory input they
pull back into dendrite.
What does the dendritic membrane do?
it sums excitatory and inhibitory information that reaches the neuron.
Histology: axon hillock
are in cell body that has no rER or golgi because that is where axon is coming off of.
stains a pale pink
Histology: Nissle bodies
stacks of rER, free ribosomes and organelles (Golgi) in cell body of neuron that produce proteins to help support axon.
chemical synapse
presynaptic (cluster of synaptic vesicles) and postsynaptic element (receptors)
Neuromuscular junction= Ach neurotransmitter
What are the two proteins in charge of helping a pre-synaptic vesicle dock on the pre-synaptic membrane of a synapse?
VAMP and t-SNAREs
- calcium sensing proteins
Where in the synaptic release process does congenital myasthenia syndrome affect?
impaired vesicle recycling
Ach not released properly
Where in the synaptic release process does LEMS attack?
Presynaptic calcium channels– antibodies
Where in the synaptic release process does Botulinum and tetanus toxic interfere with?
interfere with SNARE proteins – vesicle fusion to pre-synaptic membrane of synapse.
What are the downstream effects of a lesion of an axon?
- degeneration of distal part of axon
2. degeneration of downstream cell body (next neuron)
CNS has 4 types of support cells.
Neuroepithelium develops into–>
ependymal cells, oligodendrocytes and astrocytes
microglia
macrophage- monocyte origin.
Do not come from CNS– originates from outside of neural tube
ependymal cells
epithelial cells that line the ventricles of the brain and spinal canal (spinal cord)
picky barrier for CSF movement
Consist of microvilli and cilia
Choroid plexus
ependymal cells are modified to form special secretory epithelium.
produces CSF
Astrocytes
star shaped (histology)
lies between capillaries and neurons
lies between neurons and pia mater
Unique organelle; glial fibrillary acidic protein (GFAP) – makes up glial filaments (intermediate filaments)
serve as K+ sinks and regulate the ionic environment (via gap junctions)
Found around nodes of ranvier
Found around synapse
- may ensure OR terminate synaptic transmission
- neurotransmitter receptors on some astrocytes
Astrocytes and blood brain barrier?
Are not themselves responsible for the barrier but it does control substances necessary to make the BBB.
Astrocytes in an immune response?
divide and remove neuronal debris
oligodendrocytes
myelin producing cells of CNS
Myelination process?
oligodendrocyte sends out processes (40-50) that wrap axons in a spiral manner.
Proteolipid protein
keep two arms wrapping around axon together.
Schwann cells
support the PNS
- when associated with peripheral nerves = schwann cells
- when associated with cell bodies = satellite cells
Surround ALL peripheral neurons (myelinated or non-myelinated)
- produce growth factors and phagocytose debris at lesion sites.
- most commonly known for covering and myelinating peripheral neurons
what happens when a schwann cell is lesioned?
one Schwann cell = 1 internodal segment
Death on 1 schwann cell is not as bad as a death of an astrocyte.
Po
adhering protein of the PNS
-holds two arms of schwann cell that is wrapping around axon
histology: Endonerium
Connective tissue
- inner most coat of loose CT that surrounds axon and schwann cell
histology: perineruium
modified dense fibrous CT with contractile cells that form a semipermeable barrier
- axon (more than 1) - Schwann cell - endoneurium
form fasicles
histology : epineurium
contains many fasicles
Major differences between CNS and PNS
- CNS unmyelinated axons have no form of ensheathment
- In CNS one oligodendrocyte forms many internodes. In PNS one Schwann cell forms one internode
- PNS unmyelinated and myelinated axon are covered by Schwann cells (covered by basal lamina and CT coats)
If PNS is lesioned, reconnections between the lesioned neurons may occur IF:
If basal lamina, endoneurium, perineurium and epineurium are intact.
-grow along tubes
Schwann cells provide the growth factors.
