Exam 2 - Lecture 18 (Neuroglia 2) Flashcards
What is GDNF released by and why?
Released by astrocytes to keep properties of BBB
How do astrocytes transport glucose?
Use GLUT 1 transporter
Why do astrocytes store glycogen?
Energy reserve
How do astrocytes promote neuronal survival?
Nerve growth factor (NGF)
Where is GLUT 1 found?
perivascular end feet
What is glutamate?
NTM in the CNS
Where is glutamate released from?
terminal end of axons
What is important about glutamate at high concentrations?
It is neurotoxic
What is the space between the end of one neuron and the cell body of the next?
synapse
Describe the glutamine –> glutamate cycle in the neuron/astrocyte.
- Glutamine –> glutamate by glutaminase
- Glutamate transported to next neuron in vesicles, bind to GluR at postsynaptic neuron
- Can be transformed back to glutamine by glutamine synthetase in the astrocytic process
Where is glutamate –> glutamine?
Astrocyte
What neuroglia respond to tissue damage and remove debris by phagocytosis?
Microglia
Where are microglia found?
CNS (~20% of CNS neuroglia)
What happens to microglia once they are activated?
Proliferate and assume a phagocytic role
What stain is necessary to see microglia?
Golgi stain
Where are oligodendrocytes found and what % of their location do they make up?
Found in CNS (~30% of CNS neuroglia)
What is the function of oligodendrocytes?
Increase conduction velocity by myelinating axons that are >1 μm in diameter.
Where are Schwann cells found and what % of their location do they make up?
PNS (100% of PNS neuroglia, ONLY PNS neuroglia)
What is the myelin sheath?
Plasma membrane wrapped around an axon in a spiral fashion, effectively insulating axons from EC fluid.
Where are Nodes of Ranvier located?
Between internodes (exposed to EC space)
What is the function of Schwann cells?
Increase conduction velocity by myelinating axons that are > 1 μm in diameter.
What are the 3 steps to myelination?
- Cell processes elongate and encircle the axon
- One process starts wrapping the plasma membrane around the axon
- Exclusion of cytoplasm from encircling cell process, forming the myelin sheath
What does the myelin sheath belong to?
plasma membrane of Schwann cell
Where is the Schwann cell located in relation to the axon and myelin sheath?
On their periphery
What is the state of axons in oligodendrocytes?
They do not support axons at all
What happens to Schwann cells when axons are < 1 μm in diameter?
Support and surround axons, but no myelination
- Space around axons is open to EC space
What is the relationship between myelin and conduction speed?
Myelin present = faster conduction speed
What is the relationship between length of axon and conduction speed?
Longer axon = slower conduction speed and vv.
What c.t. surrounds nerve fibers?
endoneurium
What c.t. surrounds fascicles?
perineurium
What c.t. surrounds nerves?
epineurium
Axon + Schwann cells = ?
nerve fiber
Nerve fiber + nerve fiber + nerve fiber, etc. = ?
fascicle
fascicle + fascicle + fascicle, etc. = ?
nerve
What is a Schwannoma?
Tumor of the Schwann cell
What % of canine nervous system tumors do Schwannomas make up?
~27%
What are two other names for Schwannomas?
- Neurilemmoma
2. Neurofibroma
