Neuron Structure

Question 1

Nissl Stain

Answer 1

Only cell bodies, no processes or vasculature

Question 2

Golgi Stain

Answer 2

Shows vasculature and processes, continous web

Question 3

Neuron Doctrine

Answer 3

Individual cells on neurons

Question 4

Characteristics of Cell Body, Soma, Perikaryon

Answer 4

Euchromatin - Transcriptively active
Nissl Substance - RER strands due to translation activity
Axon hillock - No nissl substance, where axon arises
Neurofilaments - Distinctive neuronal CT useful for IDing

Question 5

Dendrite

Answer 5

Receptive sites for synapses

Dendritic spines - greater surface area, better reception

Question 6

Axon

Answer 6

Major effector site for synapses, AP conduction
Axolemma - Surface membrane of axon
Axoplasm - Ribosomes or RER

Question 7

Presynaptic Axon Terminals

Answer 7

Synaptic boutons: Synaptic end-feet

Varicosities: en passant synapses

Question 8

Unipolar or pseudounipolar

Answer 8

Sensory ganglion neurons

Question 9

Bipolar

Answer 9

Retina, olfactory neurons

Question 10

Multipolar

Answer 10

Pyramidal neurons of cerebral cortex
Purkinje cells of cerebellum
Motor neurons of spinal cord

Question 11

Axon Length Types

Answer 11

Golgi type 1 (long axons, projection neurons)

Golgi type 2 (short axons, interneurons)

Question 12

Size and shape of soma

Answer 12

Related to length and number of processes

Variable size: 5-150 micrometers

Question 13

Common organelles

Answer 13

Golgi, mitochondria, rough and smooth ER

Question 14

Nissl Substance

Answer 14

RER
Perikaryon (cell body) and dendrites
Not in axon hilock or axon
Basophilic (basic dye)

Question 15

Lysosomes

Answer 15

Storage disease: Various mutations
Lipofuscin granules: “Indigestible” lysosomal materials
Large end-stage lysosomes (resuidual bodies), associated with normal aging and dementia

Question 16

Cytoskeleton

Answer 16

Actin microfilaments (5-8 nm)
Intermediate filaments (10 nm)
Microtubules (20-25 nm)

Question 17

Microfilaments

Answer 17

5-8 nm
Most abundant protein in neurons
Polar ATPases

Question 18

Components of microfilaments

Answer 18

Globular G actin binds with ATP and polymerizes to form filamentous F actin
Cytochalasins depolymerize F actin
Phalloidin stabilizes F actin
Both drugs block filament turnover and threaten cell viability

Question 19

Polarity of microfilaments

Answer 19

Fast growing plus and a slower growing minus end

Results in a treadmilling effect

Question 20

Neurofilaments

Answer 20

Neuron specific IF
Nonpolar
10 nm
Neurofibrils are aggregates visible at light microscopy
Neurofibrillary tangles: Alzheimer’s disease

Question 21

Components of neurofilaments

Answer 21

Monomers to coiled-coil dimers to antiparallel tetramers of protofilaments to protofibril to 10 nm neurofilament
Subunits of low, middle, or high MW: 70. 140, 210 kDa

Question 22

Microtubules

Answer 22

Polar, GTPases, 20-25 nm, hollow
Present in cytoplasm of cell bodies, dendrites and axons
13 protofilaments: chains of tubulin

Question 23

Microtubules polarity

Answer 23

Plus end is rapidly growing (assembly), minus end is slow growing (disassembly)
Dendrites: Positive ends point toward the postsynaptic sites in distal dendrites
Axons: Positive ends away from the soma

Question 24

Antimiotic chemotherapeutic drugs

Answer 24

Colchicine: Depolymerizes microtubules
Taxol: Stabilizes microtubules

Question 25

Microtubules-associated proteins

Answer 25

Stabilize microtubules against abnormal disassembly

Mediate interaction of other cell components

Question 26

High molecular weight MAPs

Answer 26

200-2000 kDa
MAP-2 present only in dendrites
Kinesin mainly for transport toward end of microtubules
Cytoplasmic dynein (MAP-1C: for transport toward the minus-end of microtubules)

Question 27

Low molecular weight MAPs

Answer 27

55-62 kDa

Tau proteins: Tangles of Alzheimer’s Disease brains

Question 28

Need for transport

Answer 28

Soma site of synthesis
Axons may be up to a meter long yet need to receive soma proteins
Degraded proteins are membranes must be returned
Diffusion is too slow

Question 29

Slow axonal transport: axoplasmic flow

Slower component

Answer 29

Anterograde direction
0.2-2.5 mm/day
Cytosol: components of microtubules and neurofilaments

Question 30

Slow axonal transport: faster components

Answer 30

Rate up to 10 mm/day
Complex mixture of proteins including actin
Metabolic enzymes
Calmodulin

Question 31

Fast anterograde (orthograde)

Answer 31

Rate: 410 mm/day
ATP-dependent
Relies on microtubules and kinesin
Blocked by colchicine
Transport organelles

Question 32

Fast retrograde axonal

Answer 32

300 mm/day
ATP-dependent
Dynein
Return cell components for degradation, growth factors, viruses, toxins, experimental tracers

Question 33

Kinesin

Answer 33

Moves cargo to positive end of microtubule
2 heavy chains: globular head are motor domains, bind to both microtubules and ATP
2 light chain: bind to other cell components (vesicles and organelles)

Question 34

Dyenin (MAP-1C)

Answer 34

High MW MAP: Up to 2000 kDa
2 or 3 heavy chains: form globular ATP-binding motor domains
Variables numbers of light and intermediate chains

Question 35

Dendritic transport

Answer 35

Rate and components similar to axonal transport
All newly synthesized membranous organelles are transported from the cell body to dendrites
All degradative products are transported from the dendrites back to the cell body