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Flashcards in Neuron (LE031) Deck (12):

Describe how entry of organelles in axons is selective. Ie, which organelles are missing from the mature axon that is contained in the cell body of a neuron?

Before the axon hillock, there is a functional barrier between the cell body and the start of the mature axon such that there are no RER, ribosomes, and golgi complex in mature axons.
There is no protein synthesis in mature axons.


Why is the cell body stained dark purple in Nissl images?

RERs are stained dark purple with Nissl staining whereas axons lack the organelles that stain dark purple (RER, ribosomes, golgi complex).
Nissl staining stains acidic structures.


What is white matter made of? What is gray matter made of?

White matter: myelinated axons → propagation of signal
Gray matter: neuronal perikarya (cell body), dendrites, and synapses (integration of information)


Which cells create myelin?

CNS: Oligodendrocytes
PNS: Schwann cells


Describe the membrane cytoskeleton of neuron axons.

There are rings of actin and adducing at cross sections of the axon, connected by spectrin tetramers.


Compare the relative lengths of neuron axons.

Purkinje Cell: 36 mm
Retinal Ganglion cell: 5cm
Motor neuron: 1 m


Compare the conduction speed of unmyelinated nerves to myelinated nerves.

Unmyelinated: 0.6-2.0 m/s
Myelinated: 5-120 m/s


Where are Na+ channels most highly concentrated in a neuron?

Axon hillock
Nodes of Ranvier


Why won’t axons of the white matter of the Central Nervous System regenerate?

It is not because it does not have the intrinsic methods of regeneration. It is because the oligodendrocytes prevent regeneration.


What are astrocytes?

Astrocytes are star shaped glial cells responsible for structural support in the brain. Of note, they support endothelial cells of the blood brain barrier. They also secrete growth factors and respond to injury.


What are microglia?

They are macrophages of the brain. Resident immune cells of the CNS.


What do radial glia do?

They form tracks for neuronal migration during brain development.