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Neuro > Neurons and Glia > Flashcards

Neurons and Glia Flashcards

1
Q

What substance is used to harden the brain?

A

Paraformaldehyde

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2
Q

What is the tool used to slice the brain?

A

Microtome

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3
Q

What type of sections is the brain sliced into?

A

Sagittal and Coronal

Imbed the brain in different orientations and get thin slices

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4
Q

What is used to freeze the brain and why?

A

Crysostat is used to freeze the brain and then section it

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5
Q

What type of tissue cannot refract light?

A

Thin tissue so no contrast can be seen

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6
Q

What are the two different staining methods?

A

Nissel Stain

Golgi Stain

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7
Q

What is Nissel Staining?

A
  • First stain developed

- Stains RNA with purple dye so pyramidal images obtained

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8
Q

What is Golgi staining?

A
  • Uses silver chromate
  • Labels some neurons
  • Not very effective at initially labelling neurons but once labelled, does it in its entirety
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9
Q

What is the gap junction theory?

A

One neuron coupled to another by membrane proteins that span both cells.

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10
Q

Why are gap junctions important?

A
  • Charge flows through the neurons to another directly
  • Heart has gap junctions
  • Some cells in the brain communicate via gap junctions: astrocytes
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11
Q

Which cells in the brain communicate via gap junctions?

A

Astrocytes

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12
Q

What is the synaptic theory?

A

When AP arrives at the synapse, it converts electrical signal to chemical signal.

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13
Q

Why is the synaptic theory important?

A
  • Chemical signal interacts with receptors post-synaptically
  • Enables influx/efflux
  • Generation of second AP
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14
Q

What is fluorescent neurohistology?

A
  • Use of particular light frequencies shined through a sample -> if the sample expresses green fluorescent protein (GFP), use blue light. If it emits red light, it can be detected as a light source
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15
Q

What is removed from the brain to allow more transparency?

A

To allow for clarity - fatty tissue (myelin) is removed from the brain

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16
Q

How is green fluorescent protein obtained?

A
  • Jellyfish express GFP
  • Genetic code for GFP was identified
  • Inserted into organisms and these were made fluorescent also
  • They can express multiple fluorescent proteins and express many different wavelengths of light
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17
Q

What are opsins?

A

Light emitting proteins

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18
Q

What are the two ways opsins can be targetted to specific cells?

A

Viral delivery

Cre/lox technology

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19
Q

Explain the viral delivery of fluorescent proteins

A
  • Sequence GFP genetic code
  • Take DNA for GFP and package into the virus
  • Take out viral DNA
  • Fluorescent protein DNA code is inserted into viral DNA code along with a promoter
  • The promoter determines the cell types the virus can infect
  • The virus infects the neurons and inserts the GFP code into the DNA of the neuron.
  • The DNA transcripts and translates the GFP DNA to produce the fluorescent protein
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20
Q

Which promoter is required to target which cell types?

A

CMV/CAG -> All neurons and glia
GFAP -> Glia only
hSYN -> Neurons only
CamKII -> Excitatory neurons only

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21
Q

Explain the use of cre/lox technology for fluorescent proteins

A
  • Cre recombinase is an enzyme that recognises loxP sites on DNA
  • When the Cre enzyme encounters this region, it depends on the orientation of the site on what happens:
  • > Inversion: if two sites facing each other - gene is flipped, reverse order
  • > Deletion: if facing the same way: completely cuts out the gene in between them
  • > Translocation: if sites on different strands of DNA, cuts and swaps them.
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22
Q

Why can different modifications take place when using cre technology?

A

Different genetic modifications take place dependent upon loxP location/orientation

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23
Q

Why is cre/lox method favoured over the viral method?

A

It is more selective than viral method and can target subtypes of cells.

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24
Q

Describe the structure of the prototypical neuron

A
  • The neuronal ‘body’ containing K+ rich cytosol which is important for establishment of resting membrane potential and generation of ATP.
  • The nucleus for DNA replication and DNA transcription
  • Endoplasmic reticulum for RNA translation
  • Golgi apparatus for protein folding
  • Mitochondria as the powerhouse of the cell
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25
Q

What type of receptors do dendritic proteins contain and what does this mean for neurotransmitter release?

A

Ligand gated and GPCR expressed on dendrities; neurotransmitter is released presynaptically onto dendrities postsynaptically so need receptor sites

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26
Q

What type of receptors do axonal proteins have and why?

A

Voltage gated ion channels in the nodes of Ranvier to allow AP propogation

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27
Q

Structure of microtubules in neurons

A
  • Relatively large (20nm diameter)
  • Run the length of neurites: dendrites and axons
  • Tubulin composition which is spiral shaped
28
Q

Function of microtubules in neurons

A
  • Vital for transport of materials from the cell body such as structural proteins, neurotransmitters and organelles
  • Also transport towards the cell body such as signalling proteins, debris and used material
29
Q

Structure of actin microfilaments in neurons

A
  • 5nm diameter which is the same as the neuronal membrane
  • Numerous in neurites
  • Actin composition
30
Q

Function of actin microfilament in neurons

A
  • Provides support, helping to maintain the shape of the cell body and neurites
  • Plays a vital role in neural embryonic growth and helping to shape axons and dendrites
  • Actin skeleton within the filopodia grows or shrinks in response to chemical guidance signals
31
Q

What are tau proteins?

A

Neurofilament protein that binds together the cytoskeletal elements

32
Q

What can pathological problems with tau proteins cause?

A

Alzheimer’s and Parkinson’s disease

33
Q

What are intermediate filaments?

A
  • Composed of five proteins: NFL, NFM, NFH, internexin and peripherin
  • 10nm in diameter
  • Protein combinations dependent upon neuronal cell type and development stage
34
Q

What is the axon hillock?

A

Where EPSP and IPSP summate and an AP is fired/inhibited

35
Q

How long are axons?

A

1mm to over 1 metre in length

36
Q

What do axon branches form?

A

They form collaterals these are the main branches away from the main axon. They are at right angles to the main axon

37
Q

What is the terminal bouton?

A

The end of the axon terminal

38
Q

A bouton en passant

A

A synapse along the length of an axon

39
Q

Where are synaptic boutons?

A

They can be anywhere along the axon, they do not have to be at the end of the dendrite. Lots of axonal connections happen within the dendritic tree

40
Q

What does the axon terminal contain?

A
  • Terminal bouton
  • Many mitochondria as an energy rich process
  • Synaptic vesicles
41
Q

Function of synaptic vesicles

A

signal proteins on the surface so when the AP arrives, senses signal and receives instruction to fuse with the synapse membrane

42
Q

Why don’t axons have ribosomes?

A

Do not have ribosomes as they need space for mitochondria and vesicles

43
Q

What transports the vesicles?

A

Kinesin

44
Q

How does the axon receive other necessary things?

A

Via transport down the cytoskeleton and microtubules by kinesin proteins

45
Q

What are Kinesin proteins?

A

ATP activated proteins that ‘walk’ along microtubules carrying whatever the synaptic bouton needs

46
Q

What is anterograde transport?

A

From cell down the axon

47
Q

What is retrograde transport?

A

From bouton back to soma

48
Q

Why is retrograde transport used?

A

Useful for unwanted components as they need breaking down

49
Q

How are neurons classifed?

A

Classified by structure and gene expression

50
Q

What part of the structure is looked at to classify neurons?

A
  • Number of neurities (axons and dendrites)
  • Dendrities - dendritic tree formation; presence of spines; single dendrite not receiving from a single synapse
  • Connections: primary sensory neurons, motor neurons and interneurons
  • Axon length
51
Q

What part of gene expression is looked at to classify neurons?

A
  • Types of proteins
  • Types of neurotransmitter: GFP can be tagged to a certain protein and neurons expressing that protein are then revealed
52
Q

How are glia different to neuronal cells?

A
  • Difficult to measure responses
  • Come from the same precursors as neuronal cells
  • Same amount of glial cells as there are neuronal cells
  • Generate resting membrane potential the same as nerve cells but DO NOT generate action potential
  • Small in size
  • Communicate in slow waves of K+ concentration
53
Q

What are the 3 types of glia cells?

A
  • Astrocytes
  • Schwann cells
  • Oligodendrocytes
54
Q

Describe the structure and function of astrocytes

A
  • Control the movement of material into and out of the tissue
  • Make contact with the capillaries which induces them to form the BBB
  • Washes waste products from brain by driving the flow of fluid in and out
  • Regulate contents of the extracellular space
  • Express receptors
  • Releases neurotransmitter
  • Control the biochemical environment of the nerve cell
55
Q

How do astrocytes control the biochemical environment around a nerve cell?

A
  • Form a blanket around the soma and dendrities
  • Control electrolyte levels in the intervening extracellular space
  • Remove used neurotransmitters from synaptic clefts
  • Control synaptic development and function
  • Can be activated upon synaptic transmission of neurotransmitter
56
Q

Difference between oligodendrocytes and schwann cells

A

Oligodendrocytes myelinate neurons in the CNS and schwann cells in the PNS

57
Q

How do the oligodendrocytes and schwann cells myelinate the cell?

A

They wrap their own extracellular membrane around the nerve cell, leaving layers of the phospholipid membrane

58
Q

Function of oligodendrocytes and schwann cells

A
  • Ensure that the nerve cell is well insulated and does not leak ions
  • Speeds up conduction
  • Secrete growth factors and inhibitory factors that control the axon regeneration after injury
59
Q

What does damage to oligodendrocytes cause?

A

Multiple sclerosis

60
Q

Why is it important that axons are myelinated?

A
  • Acts as an insulation
  • Stops dissipation of current
  • Speeds up AP
61
Q

Difference between microglia and glia

A
  • Not actual glial due to them arising from the mesoderm rather than the neural tube
62
Q

What are microglia?

A

Immune cells that migrate to the CNS early in development

63
Q

Function of microglia

A
  • Help the development of neurons and monitor neuronal health
  • Become amoneboid and travel to areas of injury
  • Engulf and eliminate microbes, damaged cells and other matter
  • Secrete factors essential for recovery and repair
  • Help to fight Alzheimer;s
  • Do the function of immune cells as they are not able to cross the BBB
  • Present in deeper tissue
  • Perform immunological functions such as act phagocytes and invading pathogens; regulate apoptosis; nurture formation of new cells - neurogenesis
64
Q

What is neurogenesis?

A

The formation of new cells

65
Q

How does neuroglia check the health of nerve cells?

A

Health checks by interacting with the dendritic spines to make sure everything is working properly - if it isn’t working it induces apoptosis

66
Q

Other types of non-neuronal cells

A

Ependymal cells line the ventricles

Vascular cells deliver oxygen and remove CO2

Neuro (20 decks)

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