Download - Describe the roles of the different types of glial cells

- Describe the roles of the different types of glial cells
- there are 3 types of glial cells: astrocytes, schwann cells/oligodendrocytes and
microglial cells.
- Astrocytes have multiple functions. One function is helping to keep the integrity of
the BBB. Astrocytes’ feet wrap around the capillaries in the brain to further tighten up
the tight junctions and prevent any leakage of unwanted substances into the brain.
This helps create a very finely and tightly regulated environment and keeps out any
potential toxins. Astrocytes also release various neurotrophic factors which regulate
axonal growth and neuronal transport
- Schwann cells and oligodendrocytes form the myelin sheath around neurons which
insulates the axon and helps increase conduction speed in the axon. Neurons which
have become demyelinated can be so due to autoimmune diseases like MS and this
interferes with proper conduction of signals.
- Microglial cells are the immune cells of the CNS. They respond to insult or injury by
changing their morphology and number. However, excessive activation is deleterious
and can contribute to degeneration.
– Identify the key cellular features of a neuron, include the locations of VGIC, LGIC,
GPCR, Transporters, myelin sheath, dendrites, axon, soma
- Soma – cell body of a neuron. This is where the DNA is stored and proteins are
manufactured. Can have some axons/dendrites synapsing onto the cell body where
total signals are then added and this determines whether the signal will be sent down
this axon too – only if it reaches over the threshold
- Axon – the part of the neuron that transmits signals to other neurons. Covered in a
myelin sheath with Nodes of Ranvier between big chunks of insulation. These nodes
are densely packed with transporters and ion channels so the voltage/depolarization
skips from node to node
- Dendrites – branches of a neuron and can synapse with other dendrites, axons or cell
bodies. Pass the signal downwards to the cell body and then axon
- Myelin sheath – insulation of the axon made of multiple layers of membrane. Made
from Scwann/oligodendrocyte cells. This allows faster conduction speeds and stops
‘leakage of the signal’. Damaged in some diseases like MS. Can also be damaged by
drugs
- Transporters – located on presynaptic terminals or astrocytes. These take up the NT
after it has been released and facilitate its quick removal from the synapse. This is
important as NT concentrations can rise from nM to mM following an AP and some
NTs like glutamate can cause excitotoxicity and need to be quickly removed. Some
rely on conc gradients of other substances. Family 1 transports (GABA, glycine, 5HT,
dop etc) use 1-3Na and Cl- while family 2 transporters used for glutamate and
aspartate use 3Na+, H+ and K+ to transport NT (very powerful).
- GPCR – g protein coupled receptors are located postsynaptically and are activated
based on a signal that is communicated by the release of NT. They are 7
transmembrane domain proteins and the alpha subunit (either alpha I, s or q) acts on
adenylate cyclase to either inhibit (i) or stimulate (s) it. The betagamma subunit acts
on other enzymes and proteins
- LGIC – ligand gated ion channels use the NT to bind and then open a central pore in
the channel which allows the particular ion to pass through. These channels have
immediate responses and are also often located postsynaptically e.g. nAChRs
VGIC – voltage gated ion channels are opened and activated by voltage. E.g. Ca2+ vg ion
channels are located presynaptically. When the current comes it activates these