Neuron Structure Flashcards
Neuron
basic building blocks of the nervous system
Neuron Doctrine
neurons are individual cells
dynamic polarization
connectional specificity
3 basic parts of a typical neuron
Cell body/soma
Dendrites
Axon
What is contained in the soma?
nucleus and cytoplasmic organelles
Nissl substance
neurofilament
What is Nissl substance?
Rough ER
Where is Nissl substance absent?
axon hillock
What is the function of dendrites?
major receptive sites for synapses
Dendritic trunks
continuations of the soma
What are the parts of a dendrite?
trunks
fields
spines
What is the function of the axon?
major effector site for synapses:
conducts action potenials
What are the parts of an axon?
Initial segment
axolemma
axoplasm
axon collaterals
Initial segment
initiation of action potentials
axolemma
surface membrane of axon
axoplasm
no ribosomes or RER
Unipolar cell
Intervertebrate neuron
Bipolar cell
bipolar cells of the retina
Pseudo-unipolar cell
Ganglion cell of dorsal root
Multipolar cells
Motor neuron of spinal cord
Pyramidal cells of hippocampus
Purkinje cell of cerebellum
Golgi Type I
Projected neurons
Golgi Type II
Interneurons
Size and shape of the soma is related to:
length and number of processes
Subcellular organelles of neurons
plasma membrane
mitochondria
Golgi apparatus
RER
What is the function of lysosomes?
membrane turnover
What are Lipofuscin granules?
Large end-stage lysosomes
normal aging
accumulated in dementia
What is accumulated in dementia patients?
Lipofuscin granules
What is the function of the cytoskeleton?
maintaining the shape of neurons and their processes
What makes up the cytoskeleton?
Microtubules
Neurofilaments
Microfilament
What is most abundant in the cytoskeleton?
microfilaments
________ binds ATP and polymerize to form filamentous ________
G actin; F actin
Microfilaments have a _________ (+) end, and a __________ (-) end resulting in a _______________.
fast-growing; slow-growing; treadmilling effect
Cytochalasins
depolymerize F actin
Phalloidin
stabilizes F actin
What blocks the turnover of microfilaments and what is the result of doing such?
Cytochalasins and phalloidin
Threatens cell viability
Microfilaments
5-8 nm diameter
polar ATPases
Neurofilaments
10 nm diameter
nonpolar
Where are neurofilaments present?
In cytoplasm of cell bodies, dendrites and axons
Neurofibrils
aggregates visible at the light microscopic level
Characteristic of Alzheimer’s Disease
Neurofibrillary tangles
Microtubles
20-25 nm diameter
polar, GTPases
made of 13 protofilaments: chains of tubulin (alpha & beta)
Which way are the microtubules in axons pointed?
(+) ends are pointed away from the soma
Which way are the microtubules in dendrites pointed?
proximally: mixed polarity
distally: (+) end point toward the postsynaptic site (away from soma)
Antimitotic chemo drugs
Taxol (stabilizes microtubules)
Colchicine (depolymerizes microtubules)
Microtuble-associated proteins (MAPS)
stabilize microtubules against abnormal disassembly
mediate interaction of microtubles with other cell components
High molecular weight MAPS
Kinesin
Dynein
Low molecular weight MAPS
Tau proteins
Kinesin
transport toward the (+) end of microtubules
2 heavy chains: bind to microtubules and ATP
2 light chains: bind to other cell components
Dynein
transport toward the (-) end of microtubules
2 or 3 heavy chains
variable number of light and intermediate chains
Tau proteins
found in neurofibrillary tangles of Alzheimer’s Disease patients
What is the site of macromolecular and organellar synthesis?
soma
What are the types of axoplasmic transport?
Slow axonal transport: axoplasmic flow
Fast anterograde axonal transport
Fast retrograde axonal transport
Components of microtubules and neurofilaments, as well as, soluble proteins move by what kind of transport?
Axoplasmic flow/slow axonal transport: Slower component
Actin and calmodulin move by what type of transport?
Axoplasmic flow/slow axonal transport: Faster component
What type of transport is blocked by colchicine?
Fast anterograde axonal transport
Fast anterograde transport is ____________, relies on ___________, and transports ______________.
ATP-dependent; microtubules and kinesin; subcellular organelles
What type of transport relies on microtubules and cytoplasmic dyein?
fast retrograde axonal transport
Fast retrograde transport is responsible for transporting what?
cell components for degradation, growth factors, viruses, toxins, experimental tracers
Which type of transport is typically the fastest?
Fast anterograde axonal transport
