NEUR 0010 - Chapter2 Flashcards
What does a Nissl stain do?
Stains the nuclei of all cells, as well as the clumps (Nissl bodies) surrounding neuron nuclei
Why are Nissl stains useful?
Distinguish neurons from glia, allows for study of cytoarchitecture of brain tissue (arrangement of neurons)
What does a Golgi staid do?
Stains a small percentage of neurons, but includes their neurites
What are the two main characteristics of an axon and its branches?
Uniform diameter, branches at right angles
How many axons does a cell body usually emit?
Just one!
What is Golgi’s view of the neuron organization
Reticular doctrine: neurites fuse into a network
What is Cajal’s view of the neuron organization?
Neuron doctrine: never connect and communicate by contact rather than continuity
What does it mean to alternatively splice a segment of mRNA?
To splice out some exons with the introns, which codes for a different protein; thus the same stretch of transcripted mRNA can lead to different proteins after splicing
What organelle “abounds” in neurons?
Rough ER, more than in glial cells or non-neuronal cells
How do we know there’s tons of RER in neurons?
They’re the Nissl bodies! They get stained.
What organelle comprises Nissl bodies?
RER
Where is the major site of protein synthesis in neurons?
RER
What is the difference between proteins synthesized on free ribosomes vs RER ribosomes?
Free = stay in cytoplasm; RER = used in cell membrane or organelles, woven into the RER membrane to be transported elsewhere
Why is there so much RER in neurons?
Because RER-synth proteins are used in membranes of cells or organelles, which make special membrane proteins that are so characteristic of neurons
How does some SER impact protein translation?
Helps fold proteins that jut from the RER into their 3D structures
What does the Golgi apparatus do?
Post-translational chemical processing of proteins; sorts and delivers
What are the characteristics of microtubules in neurons?
Big, longitudinally down neurites; thick-walled pipe; composed of tubulin stacked like pearls (polymer)
What are MAPs?
Microtubule-associated proteins: regulate microtubule assembly and function; anchor microtubules to each other and neuron parts
What is tau?
Pathological changes in axonal MAP, which plays a role in Alzheimer’s dementia
What are the characteristics of microfilaments in neurons?
Thin, numerous and longitudinal in neurites; two strands of actin polymers; changes cell shape; closely associated with and anchored to the neuronal membrane
What are the characteristics of neurofilaments in neurons?
Intermediate diameter; mechanically strong; multiple subunits (three woven protein strands) stacked
What distinguishes the axon hillock from the soma?
No RER, few free ribosomes, different membrane protein composition
What are axon collaterals?
Branches of the axon; often returns to communicate with the same cell that gave rise to it, or with neighboring dendrites (recurrent collaterals)
What are recurrent collaterals?
Axon collaterals that return to the axon, or to neighboring dendrites
How is axon diameter related to impulse speed?
Thicker axon, faster impulse
What is the terminal arbor of the axon?
The area where several axon branches from the same axon connect to a dendrite/cell body in the same region
What is boutons en passant?
When axons form synapses at swollen regions along their length and then continue to terminate elsewhere
How does axon terminal cytoplasm differ from soma cytoplasm?
No microtubules, lots of synaptic vesicles, inside surface has dense protein covering, many mitochondria
What is Wallerian degeneration?
Degeneration of axons when they’re separated from the soma (because they can’t make proteins, no ribosomes)
How are proteins transported down the axon?
Walked by kinesins down the microtubules, fueled by ATP
What is the difference between anterograde and retrograde transport?
Anterograde is soma to terminal, retrograde is terminal to soma
How does transport protein involvement differ between anterograde and retrograde transport?
Anterograde recruits kinesin, retrograde recruits dynein
What are dendritic spines?
Specialized structures on some dendrites that receive synaptic input; believed to isolate various chem reactions triggered by types of synaptic activation
How do dendritic spines differ in mentally retarded infants from typically developed infants?
Less spines with metal retardation
What is the main difference in cytoplasm for axons and dendrites?
Dendritic cytoplasm can contain polyribosomes just under the spines
What is the significance of potential polyribosomes in dendritic cytoplasm?
That synaptic transmission can direct local protein synthesis in some neurons!
How does one classify neurons by number of neurites?
Single neurite = unipolar; two neurites = bipolar; more neurites - multipolar
Are the majority of neurons uni/bi/multipolar?
Multipolar
How does one classify neurons by dendrites?
By their complex shapes, or by spiny/aspinous
What are stellate vs pyramidal neurons?
Classes of neuron in cerebral cortex: star shaped or triangle shaped
How does one classify neurons based on connections?
Primary sensory neurons (neurites in sensory surfaces); motor neurons (synapse with muscles); interneurons (connect to other neurons; majority of neurons are interneurons)
How does one classify neurons based on axon length?
Golgi type 1 (long axons); Golgi tpye 2 (short axons)
What is a cholinergic neuron?
Releases acetylcholine at the synapse; includes motor neurons that command voluntary movement
What are astrocytes?
Glia: fill space, so influence neurite growth/retraction; regulates chemical content of extracellular space (like muffling synaptic junctions, removing neurotransmitters from synaptic cleft)
What is a Schwann cell or oligodendroglial cell?
Insulate axons by wrapping them in myelin, interrupted by nodes of Ranvier
How do oligodendroglia and Schwann cells differ?
Oligodendroglia are only in CNS, whereas Schwann are only in PNS; Oligodendroglia can myelinate multiple axons , but Schwann can only myelinate a single axon
What are ependymal cells?
Line fluid-filled ventricles, help direct cell migration during brain development
What are microglia?
Phagocytes to remove debris
