lecture 1 macroglia Flashcards
Structural Diversity Can be classified _____ emanating from the cell body
by shape or the number of extensions
Bipolar (interneuron)
Have one axon and one dendrite. Found in the retina, ear, olfactory lobes
Unipolar neuron:( sensory neuron)
Have one process serving both the axon and dendrite. Found in ganglia
Multipolar neuron(motor neuron)
Have three or more processes (one axon and at least two dendrites). Mostly found in the CNS
Interneurons maintain physiological activity levels in the brain, by
preventing runaway excitation in recurrent cortical networks Usually inhibitory!
Principal Cells are
axonal projections outside of the brain area where the cell bodies and dendrites are located. Local information processing and storage. Mostly Excitatory
Diversity within the Neuronal Population
structural
Shape
Organization
Diversity within the Neuronal Population (Functional)
Neurotransmitter
Peptides
Electrical Activity
Organization
how cells signals: Cellular computational capacity can be dictated by
dendritic geometry.
Macroglia: generic term
cells in the NS that are neither neurons or microglia
examples of macrogila
Schwann Cells and Oligodendrocytes Myelinating cells of the Nervous System
mylin acts like an insulator along the axon, allowing transmembrane currents at specific locations called
the nodes of Ranvier
Myelin is actually a specialized membrane that
surrounds axons, and facilitates RAPID nerve impulse conduction
Myelin is White matter of and contains
the brain and spinal cord, lipids and proteins
what 4 main ways is Myelin important for
insulate, accelerate,preserve energy, axonal maintenance
The process of _______ is one of the last events in the formation of the nervous system
myelination
In humans, myelination begins in the
third trimester, and continues to early adulthood
_____ fibers and _____ fiberes are the first to be myelinated
motor and large
Myelin is produced by ______ in the peripheral nervous system
Schwann cells
Myelin is produced by ______ in the central nervous system
oligodendrocytes
what dictates the amount wraps of mylins around a fibere
size of fibres and activity (to a pt)
g ratio
is the diameter of axon to total diameter of when its mylinated 0.6
proteins in myelin are different in
PNS and CNS and between species
saltatory conduction: In myelinated axons, channels are found only a the nodes of Ranvier. The signal
‘skips’ down the axons
continuous or contiguous conduction: In unmyelinated axons,______ event is necessary. There is___depolarization
no further triggering, passive
The presence of myelin _______ that is needed to restore the proper ionic gradients.
reduces energy consumption
Schwann cells secrete molecules that
foster axonal health and regeneration after injury
non-Myelinating Schwann Cells are called
Remaks
Multiple Schwann cells myelinate _____ but one schwann cell is _ wrap
same axon, 1
After injury, the Schwann cells____ and ____ producing agents that stimulate nerve repair.
de-differentiate and proliferate,
How do Schwann cells differentiate and produce myelin?
it requires axonal contact, and likely derives signals from the axon itself (neuron-schwann cell interactions
Neuregulin-1 are expressed on
axonal surface
________ regulate thickness of myelination produced by Schwann cells
Neuregulin (NRG) levels
NRG1 on the axon promotes Schwann cell ___&____
differentiation and proliferation.
Oligodendrocytes Myelinate segments of ___ axons
MANY up to 50
After injury, the Oligodendrocytes dedifferentiate and proliferate, producing agents that
inhibit nerve repair eg., NOGO)
Oligodendrocytes are ______ They can also differentiate in culture without neurons, in contrast to Schwann cells.
complex cells.
Oligodendrocyte development and differentiation
Early progenitors are simple and bipolar.
Differentiation in vitro is predictable and controllable
3 main take aways about Schwann Cells
1) Myelinate 1 axon segment because whole cells is in contact with axon
2) Protein composition of PNS myelin is different
3) Can promote neuronal repair after injury
3 main take aways about Oligodendrocytes
1) Myelinate many axons segments, because of the many processes it extends to contact axons
2) CNS myelin contains some unique proteins
3) Inhibits neuronal regeneration after injury
Myelination: Programmed or Plastic?
both
Multiple Sclerosis (CNS) and Guillain Barre (PNS)
Demyelinating disorders of auto-immune origin
Guillain Barre (PNS)
Weakness/tingling/numbness , can affect diaphram and breathing, people usually recover
