18.2. Different Cells of the Brain and Nervous System Flashcards
Glial cells…
Cells that support neurons.
Greater in numbers than neurons.
Have no electrical activity.
Have four main functions:
- Support and hold neurons in place (astrocytes).
- Nourish neurons, providing nutrients and oxygen.
- Provide myelin to neurons to allow saltatory conduction (Schwann and oligodendrocytes).
- Protect from pathogens (microglia).
Astrocytes…
Found in the central nervous system only.
‘Star-shaped’ cells that support and protect neurons.
They control and coordinate other glial cells.
They contribute to the blood-brain barrier, ensuring the brain is protected from toxins in the blood.
Play a role in the inflammatory response within the brain.
Their projections contact capillaries and neurons.
Schwann cells…
Found in the peripheral nervous system only.
Produce myelin, a lipid substance that wraps around neurons to allow saltatory conduction to occur.
This increases the speed of electrical conduction and energy efficiency.
Oligodendrocytes…
Found in the central nervous system only.
They are highly branched and come into contact with many axons and coat them all in myelin.
Microglia…
Act as phagocytes for the central nervous system.
They scavenge looking for bacteria and debris to ingest.
They are the primary immune defence for the CNS as very few antibodies can cross the blood-brain barrier.
They work closely with astrocytes to protect the neuron.
Blood-brain barrier…
Blood vessels in the brain contain ‘continuous’ capillaries.
These are less permeable and less leaky than other capillaries, preventing molecules from passing through.
These capillaries fit together very well in the brain, making the BBB impermeable.
It is reinforced by the sticky feet of the astrocyte projections.
CNS damage…
Following an injury, astrocytes divide and become reactive, invading the site of injury and attract microglia.
This is designed to limit the spread of injury and protect the remaining CNS.
However, it forms a ‘glial scar’ - a physical barrier to axon growth.
Cells in the area also secrete inhibitory molecules that inhibit regrowth.
PNS damage is often recoverable as it contains less specialised support cells and therefore does have a ‘glial scar’.
MS…
An autoimmune disease that destroys the myelin sheath.
This reduces the speed and success of nervous communication (as there is less saltatory conduction).
The severity of symptoms depends on the location and severity of demyelination.
