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5BBM0218 Physiology and Pharmacology of CNS > L2: Intro to glia > Flashcards

L2: Intro to glia Flashcards

1
Q

What are the two major classes of cells in the brain?

A

Neurons and Glia

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2
Q

Describe the electrical excitability of neurons and glia

A
  • Neurons are electrically excitable,
  • whereas glia are electrically non-excitable and cannot generate action potentials
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3
Q

Glia express voltage-gated channels, true or false?

A

True

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4
Q

Are glia vascular cells in the brain?

A
  • No, glia are not vascular cells
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5
Q

What is the primary function of glia in the brain?

A

Glia are the homeostatic cells of the brain

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6
Q

Name the two types of glia

A

macroglia and microglia

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7
Q

What is the origin of macroglia, and name some examples

A
  • Macroglia has a neural ectodermal origin
  • Examples include astroglia, oligodendroglia, and NG2-glia
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8
Q

What is the origin of microglia, and how do they invade the brain?

A
  • Microglia have a non-neural mesodermal origin
  • They originate from macrophages that invade the brain during fetal development
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9
Q

Name some examples of peripheral (NS) glia

A
  • Schwann cells
  • satellite cells of sensory and sympathetic
  • ganglia- olfactory ensheathing cells
  • enteric glia
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10
Q

Describe the morphology of astrocytes

A

Astrocytes have a classical star-like morphology with two types: protoplasmic and fibrous

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11
Q

What intermediate filaments do astrocytes express?

A

Astrocytes express GFAP (Glial Fibrillary Acidic Protein) as intermediate filaments

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12
Q

Where can astrocytes form processes under the surface of the brain?

A
  • Astrocytes can form processes under the surface of pia matter, forming the glial limitans
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13
Q

What do astrocytes enwrap around in the blood-brain barrier (BBB)?

A
  • Astrocytes enwrap capillaries in the BBB
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14
Q

How many dendrites of a single neuron can a single astrocyte contact?

A
  • A single astrocyte can contact multiple dendrites of a single neuron
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15
Q

Is there overlapping between astrocytes?

A
  • Usually, there is no overlapping between astrocytes
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16
Q

How many neuronal axons does an oligodendrocyte myelinate, and how close is it to the cell body?

A

An oligodendrocyte myelinates 30-50 neuronal axons within 20-30 micrometers of the cell body (soma)

17
Q

What is the function of NG2 glia?

A

NG2 glia form contacts, including synapses with neurons in grey matter, and can generate oligodendrocytes during developmental remodeling

18
Q

What is the origin of microglia, and what is their role in the brain?

A

Microglia have a mesodermal origin and form the brain’s immune system. They appear in three states: resting, active, and phagocytic

19
Q

What is the role of Schwann cells, and what are the two types?

A
  • Schwann cells have the role of myelinating and non-myelinating peripheral nerves
    -The two types are myelinating Schwann cells & non-myelinating Schwann cells
20
Q

What are the two types of synapses that connect via transcellular channels?

A

The two types of synapses are chemical synapses and electrical synapses

21
Q

The two types of synapses are chemical synapses and electrical synapses

A
  • A tripartite synapse consists of three components: the presynaptic terminal, the postsynaptic membrane, and the surrounding astrocyte process
22
Q

What triggers the release of neurotransmitters and glial transmitters in a synapse?

A
  • Calcium triggers the release of neurotransmitters and glial transmitters in a synapse
23
Q

How do glial cell receptors facilitate cell-to-cell communication?

A
  • Glial cell receptors facilitate cell-to-cell communication through ionotropic and metabotropic receptors
24
Q

What is volume transmission, and how does it occur?

A
  • Volume transmission is a slow process that involves one-to-many transmissions via diffusion
25
Q

What is wiring transmission, and how does it occur?

A
  • Wiring transmission is a rapid process that occurs via chemical synapses or electrical synapses, involving a one-to-one transmission
26
Q

Do astrocytes fire action potentials?

A

No, astrocytes do not fire action potentials.

27
Q

How do astrocytes respond to neurotransmitters and blood hormones?

A

Astrocytes respond to neurotransmitters and blood hormones by using calcium ions for signalling

28
Q

What happens when one astrocyte cell is activated by a neurotransmitter?

A
  • When one astrocyte cell is activated by a neurotransmitter, the signal spreads across other astrocytes, leading to inter-glial calcium waves
29
Q

How are inter-glial calcium waves maintained?

A
  • Inter-glial calcium waves are maintained by diffusion of a second messenger through gap junctions OR by calcium-dependent release of glial transmitters such as ATP and glutamate
30
Q

What are gliotransmitters, and what are some examples?

A
  • signaling molecules released by astrocytes
  • Examples include glutamate, ATP, and D-serine
31
Q
  • How do gliotransmitters modulate firing frequency and synaptic transmission?
A
  • Gliotransmitters such as glutamate, ATP, and D-serine can bind to respective receptors on neurons to modulate firing frequency and synaptic transmission
32
Q

Apart from gliotransmitters, what other substances do glial cells release?

A

Glial cells also release peptides such as NPY

33
Q

What is the main function of astrocytes in the brain?

A
  • support
  • homeostasis (particularly K+ buffering)
  • water regulation
  • regulation of extracellular pH
  • maintenance of the BBB properties & the astrocyte-neuronal lactate shuttle
34
Q

How do astrocytes maintain K+ homeostasis in the brain?

A
  • Astrocytes maintain K+ homeostasis by taking up K+ from the extracellular space and transporting it into the perivascular system or interstitium
  • The process involves inwardly rectifying K+ channels and gap junctions that allow K+ movement between neighboring astrocytes.
35
Q

What role does astrocytes play in water regulation in the brain?

A
  • Astrocytes regulate local shrinkage due to neurotransmitter release by accumulating water at places with high neuronal activity
  • Water is taken up by astrocytes through aquaporin 4 channels colocalized with K+ inwardly rectifying channels
36
Q

How do astrocytes contribute to the maintenance of the blood-brain barrier properties?

A
  • Astrocytes contribute to the maintenance of the blood-brain barrier properties by interacting with endothelial cells & helping to regulate the permeability of the BBB
37
Q

What is the astrocyte-neuronal lactate shuttle?

A
  • a process by which astrocytes take up glucose, convert it to lactate, and then release lactate to be taken up by neurons as an energy source
38
Q

What is the main function of oligodendrocytes in the central nervous system (CNS)?

A
  • to myelinate axons in the CNS, which helps in the rapid transmission of nerve impulses
39
Q

How do microglia respond to trauma or damage in the brain?

A
  • Microglia respond to trauma or damage in the brain by becoming activated:
  • with some aiming to destroy foreign cells
  • while others function as phagocytic cells to remove damaged cells and debris

5BBM0218 Physiology and Pharmacology of CNS (17 decks)

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