Physiology: neurons and glia

Question 1

What is the origin of glia in the - CNS?
- PNS?

Answer 1

CNS: neural plate (except microglia)
PNS: neural crest cells

Question 2

What are the 4 types of CNS glia?
2 types of PNS glia and their CNS equivalents?

Answer 2

Oligodendrocytes/Schwann cells
Astrocytes/satellite cells
Ependymal cells
Microglia

Question 3

Ratio of oligodendrites:axons and schwann cells:axons?

Answer 3

1 oligodendrycte to many axons
1 schwann cell to 1 axon

Question 4

Astrocytes
- Do they surround every synapse?
- Functions?

Answer 4

Yes; usually 2-3 astrocytic processes around each dendritic spine

• Maintains calcium and potassium concentrations in the extracellular space
• Removes NT’s, excess ions, signalling molecules from the synaptic cleft (sometimes via reuptake transporters)

Question 5

Label these neurons

Answer 5

Question 6

Differentiate projection neurons vs interneurons in terms of:
- Axon length
- Excitatory/inhibitory function in CNS

Answer 6

Question 7

AXONAL TRANSPORT
Why is it required?

Answer 7

Axons are often long and have a high volume - passive diffusion of substances is inadequate to meet energy needs.

Question 8

AXONAL TRANSPORT
What are the 2 types of axonal transport?

Answer 8

Fast axonal transport
Slow axonal transport

Question 9

AXONAL TRANSPORT
Fast axonal transport
- Which protein is involved in
- Anterograde transport
- Retrograde transport?

• Is anterograde or retrograde transport faster?
• What process can help transported structures get to their correct destination?

Answer 9

Kinesins, dyneins
Anterograde
Post translational modifications (eg. ubiquitination, phosphorylation)

Question 10

AXONAL TRANSPORT
Fast axonal transport
- How is the tetanus toxin implicated in fast axonal transport?
- How are the herpes simplex, rabies and polio viruses implicated?

Answer 10

The tetanus toxin is retrogradely transported to the soma + inhibitory neurons –> paralysis via tetanic muscle contraction

Herpes simplex, rabies and polio viruses are retrogradely transported to the soma

Question 11

SYNAPSES
What are the two types of synapses?

Answer 11

Chemical synapses
Electrical synapses

Question 12

SYNAPSES
Describe the structure of electrical synapses

Answer 12

6 connexin proteins

Question 13

SYNAPSES
What is a graded potential?
How is it different from an AP?

Answer 13

NT is released by presynaptic neuron, binds to ligand gated ion channel in dendrites of postsynaptic neuron, allowing ions to enter/exit the cell. Graded potential is the resultant change in membrane potential of the postsynaptic neuron

Can vary in size (unlike AP)

Question 14

SYNAPSES
What factors can influence whether graded potentials met the AP threshold?

Answer 14

• Past firing history
• Spatial and temporal summation
• Strength of signal
• Cell type

Question 15

SYNAPSES
Describe the frequency and strength of each type

Answer 15