Neuron Structure Flashcards
Dendrite or axon?
Can be single or multiple extensions of the cell body
Dendrite
Dendrite or axon?
Can contain all cytoplasmic organelles except for the Golgi apparatus, especially in proximal dendrites.
Dendrite
Dendrite or axon?
Tapers in a proximo-distal direction
Dendrite
Dendrite or axon?
can branch profusely and can have spines; spines contain spine apparatus and receive the bulk of the synapses
Dendrite
Dendrite or axon?
Almost never myelinated
Dendrite
Dendrite or axon?
Usually ramify close to the cell body
Dendrite
Dendrite or axon?
Responds with graded depolarization or hyperpolarizatino that decrements spatially and temporaly; some can generate action potentials
Dendrite
Dendrite or axon?
Major receptive site of synapses (postsynaptic), but may also be presynaptic
Dendrite (e.g. dendrodendritic synapses)
Dendrite or axon?
Structurally absent but functionally present in unipolar cells
Dendrite
Dendrite or axon?
Major energy consuming portion of a neuron
Dendrite
Dendrite or axon?
Single extension from the cell body or from a dendrite
Axon
Dendrite or axon?
Can contain most cytoplasmic organelles except for Golgi apparatus, rough ER, and ribosomes
Axon
Dendrite or axon?
Trunk stays cylindrical, can branch profusely
Axon
Dendrite or axon?
Terminals enlarge to form boutons that contain synaptic vesicles
Axon
Dendrite or axon?
Varicosities can occur along the trunk for en passant synapses
Axon
Dendrite or axon?
Can be myelinated or unmyelinated
Axon
Dendrite or axon?
Can ramify close to or far away from the cell body
Axon
Dendrite or axon?
APs are generated at the initial segments
Axon
Dendrite or axon?
Major effector site of synapse (presynaptic), but may also be postsynaptic (e.g. axoaxonal synapse)
Axon
Dendrite or axon?
May be absent (e.g. amacrine cells)
Axon
Dendrite or axon?
Energy consumption is low in the axon trunk, but may be low, moderate, or high in the terminals
Axon
What is the perikaryon?
Soma or cell body
Active chromatin
Euchromatin
Nissly substance is absent in which portion of the axon?
Axon hillock
Initiation of action potentials occurs here.
Initial segment of axon
The surface membrane of the axon
Axolemma
En passant synapses
Varicosities
Synaptic end-feet
Synaptic boutons (boutons terminaux)
The axoplasm lacks ________.
Ribosomes or RER
Sensory ganglion neurons have which structure type?
Unipolar or pseudounipolar
Retina & olfactory neurons have which structure type?
Bipolar
Purkinje cells of the cerebellum, pyramidal neurons of the cerebral cortex, and motor neurons of the spinal cord have which structure type?
Multipolar (most common)
Which Golgi type has long axons and projection neurons?
Golgi type I
Which Golgi type has short axons and interneurons?
Golgi type II
What are lipfuscin granules?
“indigestible” lysosomal material with pigmented inclusions
The most abundant protein in neurons.
Microfilaments
Microfilaments:
Single-stranded helix of globular ______ that binds to ATP and polymerize to form filamentous ______.
Microfilaments:
Single-stranded helix of globular G actin that binds to ATP and polymerize to form filamentous F actin.
Describe the treadmilling effect.
Microfilaments have a fast growing plus end and a slower growing minus end.
Are microfilaments polar?
Yes, they are polar ATPases.
What is the role of cytochalasins?
They depolymerize F actin.
What is the role of phalloidin?
It stabilizes F actin.
What do cytochalasins and phalloidins both do?
They both block the turnover of microfilaments and threaten cell viability.
Are neurofilaments polar?
No, nonpolar
Where are microfilaments present?
Present in cytoplasm throughout the neuron, also associated with the plasma membrane
Where are neurofilaments present?
Present in the cytoplasm of cell bodies, dendrites, and axons
Where are microtubles or neurotubles present?
Present in cytoplasm of cell bodies, dendrites, and axons
In axons, the microtuble (+) ends are pointed where?
Away from the soma
Kinesin is mainly for transport toward which end of microtubles?
Plus-end (away from soma, anterograde)
MAP-2 is present only in _________.
Dendrites
Dynein is mainly for transport toward which end of microtubles?
Minus-end (toward soma, retrograde)
Axoplasmic flow (slow axonal transport) moves only in which direction?
Anterograde
Actin, metabolic enzymes, and calmodulin (Ca++ binding proteins) are transported by:
axoplasmic transport, faster component (up to 10 mm/day)
Components of microtubles and neurofilaments and soluble proteins are transported by:
Axoplasmic transport, slower component (0.2-2.5 mm/day)
Fast anterograde transport (orthograde) is blocked by:
Colchicine
Subcellular organelles are transported by:
fast anterograde (orthograde) axonal transport
Fast anterograde/retrograde transport requires:
ATP
Kinesin has how many heavy and light chains?
2 heavy chains which bind to both microtubles and ATP
2 light chains which bind to other cellular components
Dynein (MAP-1C) has how many heavy and light chains?
2 or 3 heavy chains (form globular ATP bind motor domains)
Variable numbers of light chains (bind to other cell components)
True or false:
The rate of dendritic transport is faster than axonal transport.
False
Rate and components are similar to those of axonal transport.