Exam 2 histology of neurons Flashcards
What kind of synapse is a junction complex?
a chemical synapse
What are: (a) Electron dense material on the cytoplasmic side of membrane (b) Sites where vesicles approach and fuse with presynaptic membrane?
Presynaptic dense projections
What is are presynaptic dense projections?
(a) Electron dense material on the cytoplasmic side of membrane (b) Sites where vesicles approach and fuse with presynaptic membrane
What are the filaments found inside neurons?
Neurofilamens- intermediate filaments
What does the junctional complex consist of?
Presynaptic structure; synaptic cleft; post-synaptic structure
Which way does kinesin move?
Toward axon terminal (orthograde)
Which way does dynein move?
Toward the cell body (retrograde)
Explain the small-molecule secreting neuron?
neurotransmitter is made toward the axon terminal, vesicles are recycled constantly
explain the peptidergic secreting neuron?
Vesicles are loaded with peptides at the golgi apparatus and move toward axon; they aren’t recycled
what covers nerves in the CNS?
Oligodendrocytes
What covers nerves in the PNS?
Schwann cells
Name the layers of connective tissue that binds groups of axons?
Epineurium (outer, tough collagen), Perineurium (bundles of fascicles), Endoneurium around individual axons (delicate collagen)
What do unmyelinated fibers of the PNS consist of?
Axon, sheath of Schwann (neurilemma)
What is the sheath of schwann?
a Schwann cell that migrates from the neural crest that embraces a number of axons
What is a mesaxon?
region where lips of schwann cell cytoplasm meet
What is the bundle of remak?
collective term for a group of unmyelinated fibers encompassed by a single schwann cell
what are C fibers?
term for unmyelinated axons
What is the theory that describes how schwann cells wrap around an axon?
Jell-roll theory. Intraperiod line- former outer surfaces of schwann cell membranes that have fused. Major dense line: cytoplasmic surfaces of schwann cell membrane
What are regions where Schwann cells meet itself as it encircles the axon?
Internal and external mesaxons
What are nodes of Ranvier?
spaces between Schwann cells that are rich in Na channels
T/F: there are synapses in the sensory ganglia
False; sensory ganglia neurons only contain pseudounipolar cell bodies
Why can PNS neurons regenerate but CNS cannot?
Schwann cells help to make a tube-like structure that the nerve can make. Oligodendrocytes do not make this structure because of they cover multiple axons
Describe Wallerian or orthograde degeneration
Axon, axon terminals and myelin disintegrate; schwann cell sheath and connective tissue layers remain in PNS, phagocytosis by astrocytes and microglia in CNS, macrophages in PNS
Describe retrograde degeneration
Degenerative changes in the cell body and or portion of axon still attached to cell body; Chromatolysis (cell body and nucleus swell, nucleus becomes eccentric, RER disintegrates and moves to periphery)
Describe plasticity in CNS
Severing axon of one neuron can allow the creation of a collateral sprouting on a second neuron to innervate target. There is also a lot of redundancy in CNS
where are pyramidal cells found?
cerebral cortex
Does the gray matter of the cerebral cortex stain light or dark pink?
Light pink
What are the phagocytes in the CNS?
microglial cells
What type of cells lay between the granular layer and the molecular layer of the cerebellum? Where do their dendrites extend to?
Purkinje cells
What cells line central canal of spinal cord?
Ependymal cells
What is the pink stuff that you see in almost all cells. It’s axons and other cellular debris?
Neuropil
Explain the different classifications of axons
A and B are both myelinated, A>B, C is the smallest and doesn’t have myelin
What are the functions of astrocytes?
Structural support, uptake of excess potassium, ends wrap around blood vessels to form layer outside basement membrane to help make tight junctions
What is the Nissl substance? What is it made of?
dark staining features in the cell body, rough endoplasmic reticulum
What stains the Nissl substance?
Basophilic substances such as methylene blue and toluene blue
What is the wear and tear protein and how does it stain in an H&E stain?
Lipofuscin; brown
