There is a brief description of the Cytoskeleton of the neurons and glia. Functions of the different components of the Cytoskeleton. Like microtubules, microfilaments ,neurofilaments and glial filaments . Their is a brief description of the structures of the different components of the Cytoskeleton of neurons and glia.

1. The Cytoskeleton of neurons
and glia
Presented by Ritu
Reg no. 230548005
MNNT , Ist sem

2. • Cytoskeleton is a network of protein filaments within a cell that provides
structural support , helps with cell motility and maintain cell shape .
• Proteins of the cytoskeleton play a central role in the creation and
maintenance of cell shapes in all tissues.
• They provide structural organization for the cell interior , helping to
establish metabolic compartments.
• They also serves as tracks for intracellular transport , which creates and
maintains differentiated cellular functions.
• The cytoskeleton comprises the core framework of cellular morphologies.

3. Components of cytoskeleton
• Microtubules ( MTs )
• Neurofilaments ( NFs )
• Microfilaments ( MFs )

5. Microtubules
• Microtubules act as both dynamic structure elements and tracks for
organelle traffic.
• The core structure is a polymer of 50 kDa tubulin subunits.
• Heterodimers of alpha and beta tubulin align end to end to form
protofilaments , 13 of which join laterally to form a hollow tube
within outer diameter of 25 nm.
• The beta subunit is exposed at the ‘ plus ‘ end which is the preferred
end for addition of tubulin dimers. The opposite ‘ minus ‘ end grows
more slowly at physiological contractions of tubulin.

6. In glia
• In glia and most other non- neuronal , however, the minus end of MTs
are usually bound at the site of nucleation which is associated with
the centrosome or pericentriolar complex of the cell , a site often
called the microtubulicle organizing centre ( MTOC ) .
• Anchoring of nucleation of microtubules appear to required a third
class of tubulin , Y- tubulin , which is detectable only as part of the
pericentriolar complex .

7. In neuron
• Axonal and dendritic MTs are not continuous back to the cell body nor are
they associated with any visible MTOC .
• Axonal MTs can be more than 100 micrometre long , but they have
uniform polarity with all plus ends distal to cell body .
• Dendritic MTs are typically shorter and often exhibit mixed polarity , with
only about 50% oriented plus end distal.
• Brain MTs contain tubulins of many different isotopes with many different
post translational modifications and also have a variety of associated
proteins ,( MAPs ) .
• Stability is due to MAPs.
• MAP -2 is only present in dendrites and MAP-3 and tau is only present in
axon.

10. Functions of MTs
• Transport of membrane bound organelle.
• Extension of neurites during development.
• Structural basis for maintaining neurites after extension.
• Help in maintaining the definition of integrity of intracellular
compartments.

11. Microtubules ,
Microfilaments
and
intermediate
filaments in the
nervous system

12. Intermediate filaments
• Neuronal and glial intermediate filaments provide support for
neuronal and glial morphologies.
• Core rod domain , which contain multiple alpha helical domain that
can form coiled or coils.
• 8-10 nm rope like filament.
• Neuronal intermediate filaments ( NFs ) can be hundreds of
micrometres long and have characteristic side arm projections while
filaments in glia or other non-neuronal cells are shorter and lack side
arms .

13. • The primary type of IF in large myelinated axons is formed from three
subunits proteins known as the Neurofilament triplet :
• NF high molecular weight subunit ( NFH -180-200 kDa )
• NF middle molecular weight subunit ( NFM – 130-170 kDa )
• NF low molecular weight subunit ( NFL – 60-70 kDa )
• NFM and NFH also have long carboxy-terminal regions , which
projects from the core filaments as side arms .

14. Functions of IFs
• Ifs in both glia and neurons contribute to the distinctive morphologies
of those cells .
• Provide mechanical strength and a stable cytoskeletal frame.
• NFs plays an important role in regulating cellular and axonal volume.
• NFs are a primary determinant of axonal caliber in large fibers.
• NFs exhibit an unusual depree of metabolic stability which makes
them well suited for a role in stability and maintaining neuronal
morphology.

15. Microfilaments
• Actin Microfilaments and the membrane cytoskeleton play critical
role in neuronal growth and secretion.
• MFs are formed from 43 kDa actin monomers that are arranged like
two strings of pearls intertwined into fibrils 4-6 nm diameter.
• Enriched in cortical region near the plasmalemma.
• Concentrated in presynaptic terminals , dendrites spines and growth
concentration.
• Play important role in Golgi complex morphology.
• Actin Associated proteins ( Spectrin and Myosin) .

16. Functions of MFs
• The neuronal membrane cytoskeleton plays a role in maintaining the
distribution of plasma membrane proteins establishing cell
morphologies and segregating axonal and dendritic protein into their
respective compartments.
• Mediate the interaction between neurons and extracellular matrix
external world and neighbouring cells.
• In neurons and glia, adhesion site directly or indirectly interest with
MFs.

17. Thank you