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introduction to neuroscience > cells of the nervous system > Flashcards

cells of the nervous system Flashcards

1
Q

what are the 4 major compartments of the neuron

A
  1. cell body, soma, perikaryon
    neurites:
  2. dendrites
  3. axons
  4. presynaptic terminal
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2
Q

where does the axon begin?

A

the axon hillock

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3
Q

features of axon

A
  • no RER and no free ribosomes (no protein synthesis)
  • membrane composition different to some membrane
  • <1 mm to >1m in length
  • 1 microm - 25 micom diameter (in humans)
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4
Q

what are the branches of axons called?

A

axon collaterals

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5
Q

what is the end of the axon called?

A

axon terminal or terminal bouton

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6
Q

what happens at the axon terminal?

A

it is a site where the axon comes into contact with other neurons and passes information on to them (synaptic terminal)

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7
Q

what is the segment after the axon hillock?

A

axon initial segment

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8
Q

what are specializations of the presynaptic terminal cytoplasm?

A
  • no microtubules
  • synaptic vesicles
  • specialised proteins
  • mitochondria
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9
Q

what are neurons?

A

excitable cells that conduct impulses

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10
Q

what is the purpose of neurones?

A

to integrate and relay information within a neural circuit

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11
Q

what are glia?

A

supporting cells, the ‘glue’

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12
Q

what is the purpose of glia?

A

maintain homeostasis, protection, assist neural function

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13
Q

what are the components of the soma?

A
  • nucleus
  • organelles for protein synthesis and processing
    • ribosomes
    • RER
    • golgi apparatus
  • mitochondria
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14
Q

what is Nissl staining?

A
  • applying positive dye to distinguish between neurons and glia
  • nucleolus of all cells stained
  • neurons also have nissl bodies
  • nissl stain binds to RNA
  • also used to determine cytoarchitecture
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15
Q

what is a neurite?

A

any processes that come off of a neuron e.g. dendrites and axons

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16
Q

what is a golgi stain?

A
  • silver chromate applied to brain tissue
  • small percentage of neurons appeared but they were in more detail
  • led to neuron doctrine (gaps between neurones)
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17
Q

what are the features of the cytoskeleton in neurites?

A
  • microtubules
  • microfilaments
  • neurofilaments
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18
Q

features of microtubules

A
  • composed of polymers of tubulin molecules
  • longitudinally down neurites
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19
Q

features of microfilaments

A
  • polymers of actin
  • longitudinally and membrane associated
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20
Q

features of neurofilaments

A
  • long protein molecules, wound together
  • very strong
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21
Q

what is immunohistochemistry?

A
  • used to located protein of interest e.g. voltage-gated sodium channels
  • primary antibody specific to protein of interest
  • fluorescent secondary antibody specific to primary antibody
  • used on fixed tissue (not live)
22
Q

what does it mean if an axon has many collaterals?

A

it has a high level of divergence, it can contact many cells

23
Q

what are specialisations of the presynaptic terminal cytoplasm?

A
  • no microtubulues
  • many synaptic vesicles
  • specialised proteins in the membrane
  • mitochondria
24
Q

what do many dendritic branches form?

A

dendritic trees / dendritic arbours

25
Q

what do dendrites allow?

A

convergence of signals, can receive inputs from many neurons which they process and converge into one cell

26
Q

what is live fluorescent imaging?

A
  • technique to visualise neurones
  • microelectrode with fluorescent protein inject fluorescent protein into neuron
  • live imagine - in a live tissue
  • can be genetically encoded
27
Q

what are the functions of dendritic spines?

A
  • increase surface area
  • plastic - can be absorbed or grown to increase or decrease activity
  • isolate chemical reactions
28
Q

how are proteins transported from soma to presynaptic terminal?

A
  • fast axoplasmic transport
  • microtubules act as roads along axons
  • kinesin attach to microtubules and walk along them
  • this process is ATP dependent
  • anterograde transport
  • retrograde transport by dynein is when proteins move from terminal to soma (opposite)
29
Q

what are retrograde and anterograde tracers?

A
  • radioactive amino acids
  • retrograde used to locate cell body
  • anterograde used to locate cell terminals
30
Q

how are neurons classified?

A

by structure and by gene expression

31
Q

how can neurons be classified by structure?

A
  • number of neurites
  • dendritic geometry
  • connections - where do they project?
  • axon length
32
Q

how can neurons be classified by gene expression?

A
  • underlies structural differences
  • defines neurotransmitter expression (excitatory or inhibitory)
33
Q

features of unipolar neurons (pseudounipolar)

A
  • dorsal root ganglion cell
  • one central process that splits into two peripheral processes
  • small are for receiving synaptic input = highly specialised function
  • reliable relay of information
34
Q

features of bipolar neurons

A
  • e.g. retinal bipolar cells
  • small area for receiving synaptic input = highly specialised function
  • reliable relay of information
35
Q

features of multipolar neurons

A
  • e.g. purkynje cell
  • majority of neurons in the brain
  • large area for receiving synaptic input
  • high levels of convergence
36
Q

what is a stellate? (multipolar neurons)

A

star shaped dendritic tree

37
Q

what is a pyramidal cell? (multipolar)

A
  • basal dendrites that come out of cell body
  • long dendrite that becomes an apical tree at the top
  • pyramidal shaped soma
38
Q

how can neurons be classified by their projections?

A
  • sensory
  • motor
  • interneuron
39
Q

what is an interneuron?

A
  • connect one neuron to another neuron
  • largest class of neuron
40
Q

what are the two types of interneuron?

A
  • relay/projection neurons = connect brain regions
  • local interneurons = short axons, process info in local circuits
41
Q

6 functions of astrocytes

A
  • control environment surrounding neurons (maintain homeostasis)
  • act as fuel suppliers
  • regulate neurotransmitter activity
  • buffer extracellular potassium
  • form part of blood brain barrier
  • couple neuronal activity to blood supply
42
Q

features of astrocytes

A
  • found in spatial domains - processes that extend out that dont over lap
  • unique marker - glial fibrillary acidic protein (GFAP)
43
Q

what are ependymal cells?

A

type of astrocyte that lines the ventricles and central canal

44
Q

how do astrocytes act as fuel suppliers?

A
  • glycogen stores in the brain
  • glycogen converted to lactate when needed
45
Q

what is a tripartite synapse?

A

an astrocyte is in the synapse and acts as a third element

46
Q

what is the role of an astrocyte in a tripartite synapse?

A
  • terminates neurotransmitter activity
  • recycle neurotransmitters to presynaptic terminals
  • astrocytes have receptors too so can respond to neurotransmitter
47
Q

what are microglia?

A

macrophages of the CNS

48
Q

what is the function of microglia?

A
  • tissue surveillance and phagocytosis (they engulf and break down debris from cells)
  • neural development
  • synaptic pruning (remove unwanted dendrites)
49
Q

what are oligodendrocytes?

A

form myelin sheaths in CNS
- unlike schwann cells one oligodendrocytes myelinates many axons

50
Q

what are schwann cells

A

form myelin sheaths of PNS
- one schwann cell provides one myelin segment to a single axon

51
Q

how is the myelin sheath formed?

A
  • oligo cytoplasm wraps around many times around the axon
  • cytoplasm squeezed out of layers by compaction
  • myelin sheaths maintain contact with glial cells for nourishment

introduction to neuroscience (22 decks)

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