03 Neuron structure Flashcards
Reticular theory vs Neuron Doctrine
Reticular theory: all neurons connected (wrong)
Neuron doctrine: neurons are individual cells (correct)
Nissl Substance, what and where
stacks of RER, only in soma
axon collateral
smaller axons that branch off the main axon
Varicosities
En Passant synapses
Golgi I vs Golgi II neurons
Golgi I: projection neurons (very long)
Golgi II: interneurons
Most energy consuming part of neuron
Dendrites, b/c energy for repolarization
Organelles in neuron soma
Mito, Golgi, RER, nucleus, ..
Lysosome function in neurons
-Numerous and very important to dispose of excess proteins b/c neurons do not undergo mitosis. Altered lysosome fxn contributes to buildup of proteins and NG disease.
Lipofuscin granules
- large end stage lysosomes
- associated with normal aging
- accumulates in dementia
microfilament binding process
- globular (G) actin binds ATP,
- polymerizes into F actin
- Treadmilling + and - ends.
Toxins against microfilaments
- cytochalasins-depolymerize F actin
- phalloidins-stabilize F actin
both block turnover of microfilaments
neurofilament binding process
1-monomers 2-coiled coil dimers 3-antiparallel tetramers 4-protofibrils 5-neurofilament
neurofilaments and Alzheimer’s?
NFTs–neurofibrillary tangles–are hallmarks of Alzheimer’s
Microtubule binding process
- GTPases, alpha + beta Tubulin heterodimer binds GTP –> polymerization
- hydrolysis of GTP –> depolymerization
- end assembly
- end disassembly
- end assembly
Toxins against microtubules
- Colchicine–depolymerizes MT
- Taxol–stabilizes MT
both are antimitotic, used in chemotherapy
MAPs:
- purpose
- high MW?
- low MW?
Microtubule associated proteins:
-stabilize microtubules against abnormal disassembly
High MW:
- MAP-2, only in dendrites
- Kinesin, anterograde
- Dynein, retrograde
Low MW:
-Tau (hyperphosphylated found in NFTs of Alzheimer’s)
Types of Axoplasmic transport
-speed?
- Axoplasmic flow (slow)
- slow component - 2mm/day
- –soluble proteins, uses MT and NF
- fast component - 10 mm/day - Fast anterograde-16’‘/day
- Kinesin on MT - Fast retrograde - 12’‘/day
- Dynein on MT
Kinesin
- Function
- structure
- weight
Kinesin
-anterograde axon transport
- 2 heavy chains–motor, bind to MT, ATP
- 2 light chains–bind to vesicles, organelles
-360 kDa (high MW MAP)
Dynein
- function
- structure
- weight
Dynein
-retrograde
- 2-3 heavy chains: motor, bind to MT, ATP
- variable # of light chains: bind vesicles
-2000 kDa (high MW MAP)
Dendrites vs Axons: organelles not contained
Dendrites: All organelles except Golgi
Axons: No Golgi, RER, ribosomes
