03 Neuron structure

Question 1

Reticular theory vs Neuron Doctrine

Answer 1

Reticular theory: all neurons connected (wrong)

Neuron doctrine: neurons are individual cells (correct)

Question 2

Nissl Substance, what and where

Answer 2

stacks of RER, only in soma

Question 3

axon collateral

Answer 3

smaller axons that branch off the main axon

Question 4

Varicosities

Answer 4

En Passant synapses

Question 5

Golgi I vs Golgi II neurons

Answer 5

Golgi I: projection neurons (very long)

Golgi II: interneurons

Question 6

Most energy consuming part of neuron

Answer 6

Dendrites, b/c energy for repolarization

Question 7

Organelles in neuron soma

Answer 7

Mito, Golgi, RER, nucleus, ..

Question 8

Lysosome function in neurons

Answer 8

-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.

Question 9

Lipofuscin granules

Answer 9

• large end stage lysosomes
• associated with normal aging
• accumulates in dementia

Question 10

microfilament binding process

Answer 10

1. globular (G) actin binds ATP,
2. polymerizes into F actin
   - Treadmilling + and - ends.

Question 11

Toxins against microfilaments

Answer 11

• cytochalasins-depolymerize F actin
• phalloidins-stabilize F actin

both block turnover of microfilaments

Question 12

neurofilament binding process

Answer 12

1-monomers
2-coiled coil dimers
3-antiparallel tetramers
4-protofibrils
5-neurofilament

Question 13

neurofilaments and Alzheimer’s?

Answer 13

NFTs–neurofibrillary tangles–are hallmarks of Alzheimer’s

Question 14

Microtubule binding process

Answer 14

1. GTPases, alpha + beta Tubulin heterodimer binds GTP –> polymerization
2. hydrolysis of GTP –> depolymerization
3. • end assembly
     - end disassembly

Question 15

Toxins against microtubules

Answer 15

• Colchicine–depolymerizes MT
• Taxol–stabilizes MT

both are antimitotic, used in chemotherapy

Question 16

MAPs:

• purpose
• high MW?
• low MW?

Answer 16

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)

Question 17

Types of Axoplasmic transport

-speed?

Answer 17

1. Axoplasmic flow (slow)
   - slow component - 2mm/day
   - –soluble proteins, uses MT and NF
   - fast component - 10 mm/day
2. Fast anterograde-16’‘/day
   - Kinesin on MT
3. Fast retrograde - 12’‘/day
   - Dynein on MT

Question 18

Kinesin

• Function
• structure
• weight

Answer 18

Kinesin

-anterograde axon transport

• 2 heavy chains–motor, bind to MT, ATP
• 2 light chains–bind to vesicles, organelles

-360 kDa (high MW MAP)

Question 19

Dynein

• function
• structure
• weight

Answer 19

Dynein

-retrograde

• 2-3 heavy chains: motor, bind to MT, ATP
• variable # of light chains: bind vesicles

-2000 kDa (high MW MAP)

Question 20

Dendrites vs Axons: organelles not contained

Answer 20

Dendrites: All organelles except Golgi
Axons: No Golgi, RER, ribosomes