08a: Neurons Flashcards
Characteristic nuclear morphology.
Large, spherical, euchromatic; prominent nucleolus
“Clumps” in neuron cytoplasm are (X), formally termed (Y).
X = rER Y = Nissl bodies
In Golgi stain, (X)% of neurons are stained.
X = 1-5
Dendrites contain which intracellular structure(s)?
Mitochonria, ribosomes, and sometimes rER
(Axons/dendrites) are tapered.
Dendrites
Axons contain which intracellular structure(s)?
Mitochondria, cytoskeleton
(Axons/dendrites) don’t stain with basic dyes because:
Axons; no rER or free ribosomes
What’s the difference in morphology of the pre- and post-synaptic membranes?
Post-synaptic membrane contains many folds (to increase surface area), unlike pre-synaptic membrane
The “supporting cells” of the CNS.
- Oligodendrocyte
- Astrocyte
- Microglia
Nuclear morphology of oligodendrocytes.
Small, heterochromatic
Astrocyte function:
- Maintain stable microenvironment around neurons
2. Physical support
Nuclear morphology of astrocytes.
Small, heterochromatic
Microglial cells function:
Defense/immune
In CNS, (X) is responsible for myelin synthesis.
X = oligodendrocyte
In CNS, (X) are part of the mononuclear phagocyte system, along with (Y).
X = microglial Y = osteoclasts, macrophages
T/F: All CNS cells born/develop in CNS.
False - microglia born in marrow and migrate to CNS
In CNS, (X) picks up excess NT.
X = astrocytes
Astrocytes contain (X), which are responsible for giving CNS structure.
X = Glial Fibrillary Acidic Protein (bundles of intermediate filaments)
What are some characteristics of microglia morphology?
Small size; cytoplasmic inclusions
In CNS, (X) covers most free surfaces.
X = astrocytes
In PNS, (X) is responsible for myelin synthesis.
X = Schwann cell
One Schwann cell myelinates (X) number of internode(s).
X = one
In PNS, each internode is myelinated by (X) number of (Y).
X = one Y = Schwann cell
In PNS, each (myelinated/unmyelinated) axon is enclosed by (X). For what?
Both;
X = Schwann cell
Physical support
The Endoneurium is:
the CT found within nerve fascicle (in PNS)
Endoneurium is comprised of:
Type 3 collagen fibrils
Endoneurium runs (perpendicular/parallel) to nerve fibers.
Encircles and runs parallel
Endoneurium is bound to (X) of (Y) cells.
X = external lamina Y = Schwann
Perineurium is:
CT that encircles and groups each fascicle (in PNS)
Perineurium is comprised of:
1-5 layers of squamous cells, separated by collagen fibrils
Epineurium is:
CT that binds fascicles together, into bundle
Epineurium is comprised of:
Dense CT and some adipose
Epineurium is bound to (X) surrounding tissue.
None; no coherent boundary with surrounding tissue
Satellite cells in (CNS/PNS) are a subclass of (X). Where are they located? What’s their function?
PNS;
X = Schwann cells
Surround neuronal cell bodies and control microenvironment
Maintaining stable microenvironment in PNS involves (X) transport by (Y) cells.
X = active Y = perineurial
In PNS, which intercellular junctions are important for maintaining stable microenvironment? Why?
Tight junctions; separate endoneurial tissue fluid from fluid surrounding nerve fascicle
The tight junctions in PNS are formed by (X) cells.
X = perineurial
List the cells that reside in a nerve fascicle.
- Schwann
- Fibroblasts
- Macrophages
- Mast cells
Most, (X)%, of cells in nerve fascicle are (Y).
X = 90 Y = Schwann
In PNS, (X) is responsible for defense/immune function.
X = the immune system
T/F: Both CNS and PNS are unique in that CT isn’t responsible for providing structure/support.
False - physical support of PNS relies on CT
In peripheral nerve injury, retrograde reaction involves (X) part of neuron and anterograde reaction involves (Y) part of neuron.
X = (proximal) axon Y = (distal) axon
Axonal disintegration occurs (X) hours after injury.
X = less than 24
Describe steps in anterograde degeneration of neuron.
- Myelin pinched off from Schwann cell
- BBB disrupted along entire nerve
- Influx of additional macrophages
Describe nuclear morphological changes in retrograde degeneration of neuron.
- Peripheral movement of nucleus
- Dissolution of Nissl bodies
- Stripping of synapses from dendrites/soma
In peripheral nerve injury, division of (X), forming (Y), begins the regeneration of the axon. This occurs in (proximal/distal) neuron.
X = Schwann cells Y = Schwann/endoneurial tubes
Distal
In peripheral nerve regeneration, how do the two severed ends find each other?
- Schwann/endoneurial tube secretes growth factors that attract proximal axon sprouts
- Neuritic sprout tips love laminin (major glycoprotein in external lamina)
Traumatic neuroma occurs when:
Sprouting axon cannot reach Schwann cell tubes
List some reasons why nerve regeneration in CNS is (more/less) favorable than in PNS.
Less - extremely rare
- External lamina doesn’t exist to guide axon sprouts
- CNS myelin inhibitor of axonal growth (unlike Schwann cells)
- Astrocytes fill spaces, forming barrier (gliotic scar)
