glia form and function

Question 1

what are the different types of myelinating cells

Answer 1

1. Schwann cells (PNS)
   one per axon
2. Oligodendrocytes (CNS)
   one for multiple axons

Question 2

def of nerve

Answer 2

bundle of axons (full of lots of neruones)

Question 3

what is the role of myelinating cells in axon regeneration after injury

Answer 3

in PNS
- Schwann cells and endoneurial tubes encourage regrowth
REGENERATION POSSIBLE

in CNS
- no endoneurial tubes so no regeneration occurs

Question 4

what are endoneurial tubes?

Answer 4

endoneurial tubes present in the endoneurium layer of nerve s

Question 5

what is the role of ependymal cells in CNS

Answer 5

• form walls of ventricles in brain and spinal cord canal
• produces CSF ( cerebrospinal fluid)
• ciliated cells -> aids circulation of CSF

Question 6

what is the strucutre of astrocytes

Answer 6

• largest glial cells
• stellate morphology
  contain end feet
• protect the synapses and allow connections between neurones/astrocytes

Question 7

what is the general function of astrocytes

Answer 7

1. neuronal guidance (in developement)
2. architecture of brain and spinal cord
3. astroglia stem cells (adult neurogenesis and gliogensis)
4. homeostatic mechanism
5. controlling the synapse
6. protects the synapse
7. neurovascular coupling

Question 8

how do astrocytes function in maintaining homeostasis of neuronal cells

Answer 8

• K+ buffering in ECF (extracellular fluid)
• expresses K+ transporters to prevent the accumulation of K+ from neuron firing (not channels)

Question 9

how do astrocytes work to control the synapse

Answer 9

• they express neurotransmitter transporters which prevent diffusion outside of synapse
  -> prevents those neurotransmitters binding to other axons

Question 10

how do astrocytes work to protect the synapse against external environment

Answer 10

surrounds synapse and expresses various transporters
- these prevent entry from outside synapse reaching the synapse
protecting synapse from ECF

Question 11

how does the astrocyte function in neurovascular coupling

Question 12

how do astrocytes respond to insult to the neurone

Answer 12

damaged cells release ATP into ECF
- astroyctes increase in size (hypertrophy) and proliferation
form a glial scar around injury site

Question 13

how do microglia respond to insult on the axon

Answer 13

1. motile processes monitor environment
   danger signals or injury = transformation to activated microglia
   activated microglia perform
2. proliferation
3. release pro-inflammatory signalling substances

Question 14

what is the strucutre of microglia cells

Answer 14

• smallest glial cells
  resident immune component cell in CNS -> receptors

Question 15

what are activation stimulus for microglia

Answer 15

• tissue injury (ATP)
• pathogen derived triggers (LPS, viral coats)
• neuronal signalling (ATP)

Question 16

Features of reactive gliosis

Answer 16

• glial cells response to CNS injury involves changes to astrocytes and microglia