cells of the nervous system Flashcards
(51 cards)
1
Q
what are the 4 major compartments of the neuron
A
- cell body, soma, perikaryon
neurites: - dendrites
- axons
- presynaptic terminal
2
Q
where does the axon begin?
A
the axon hillock
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)
4
Q
what are the branches of axons called?
A
axon collaterals
5
Q
what is the end of the axon called?
A
axon terminal or terminal bouton
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)
7
Q
what is the segment after the axon hillock?
A
axon initial segment
8
Q
what are specializations of the presynaptic terminal cytoplasm?
A
- no microtubules
- synaptic vesicles
- specialised proteins
- mitochondria
9
Q
what are neurons?
A
excitable cells that conduct impulses
10
Q
what is the purpose of neurones?
A
to integrate and relay information within a neural circuit
11
Q
what are glia?
A
supporting cells, the ‘glue’
12
Q
what is the purpose of glia?
A
maintain homeostasis, protection, assist neural function
13
Q
what are the components of the soma?
A
- nucleus
- organelles for protein synthesis and processing
- ribosomes
- RER
- golgi apparatus
- mitochondria
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
15
Q
what is a neurite?
A
any processes that come off of a neuron e.g. dendrites and axons
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)
17
Q
what are the features of the cytoskeleton in neurites?
A
- microtubules
- microfilaments
- neurofilaments
18
Q
features of microtubules
A
- composed of polymers of tubulin molecules
- longitudinally down neurites
19
Q
features of microfilaments
A
- polymers of actin
- longitudinally and membrane associated
20
Q
features of neurofilaments
A
- long protein molecules, wound together
- very strong
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
what do dendrites allow?
convergence of signals, can receive inputs from many neurons which they process and converge into one cell
26
what is live fluorescent imaging?
- technique to visualise neurones
- microelectrode with fluorescent protein inject fluorescent protein into neuron
- live imagine - in a live tissue
- can be genetically encoded
27
what are the functions of dendritic spines?
- increase surface area
- plastic - can be absorbed or grown to increase or decrease activity
- isolate chemical reactions
28
how are proteins transported from soma to presynaptic terminal?
- 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
what are retrograde and anterograde tracers?
- radioactive amino acids
- retrograde used to locate cell body
- anterograde used to locate cell terminals
30
how are neurons classified?
by structure and by gene expression
31
how can neurons be classified by structure?
- number of neurites
- dendritic geometry
- connections - where do they project?
- axon length
32
how can neurons be classified by gene expression?
- underlies structural differences
- defines neurotransmitter expression (excitatory or inhibitory)
33
features of unipolar neurons (pseudounipolar)
- 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
features of bipolar neurons
- e.g. retinal bipolar cells
- small area for receiving synaptic input = highly specialised function
- reliable relay of information
35
features of multipolar neurons
- e.g. purkynje cell
- majority of neurons in the brain
- large area for receiving synaptic input
- high levels of convergence
36
what is a stellate? (multipolar neurons)
star shaped dendritic tree
37
what is a pyramidal cell? (multipolar)
- basal dendrites that come out of cell body
- long dendrite that becomes an apical tree at the top
- pyramidal shaped soma
38
how can neurons be classified by their projections?
- sensory
- motor
- interneuron
39
what is an interneuron?
- connect one neuron to another neuron
- largest class of neuron
40
what are the two types of interneuron?
- relay/projection neurons = connect brain regions
- local interneurons = short axons, process info in local circuits
41
6 functions of astrocytes
- 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
features of astrocytes
- found in spatial domains - processes that extend out that dont over lap
- unique marker - glial fibrillary acidic protein (GFAP)
43
what are ependymal cells?
type of astrocyte that lines the ventricles and central canal
44
how do astrocytes act as fuel suppliers?
- glycogen stores in the brain
- glycogen converted to lactate when needed
45
what is a tripartite synapse?
an astrocyte is in the synapse and acts as a third element
46
what is the role of an astrocyte in a tripartite synapse?
- terminates neurotransmitter activity
- recycle neurotransmitters to presynaptic terminals
- astrocytes have receptors too so can respond to neurotransmitter
47
what are microglia?
macrophages of the CNS
48
what is the function of microglia?
- tissue surveillance and phagocytosis (they engulf and break down debris from cells)
- neural development
- synaptic pruning (remove unwanted dendrites)
49
what are oligodendrocytes?
form myelin sheaths in CNS
- unlike schwann cells one oligodendrocytes myelinates many axons
50
what are schwann cells
form myelin sheaths of PNS
- one schwann cell provides one myelin segment to a single axon
51
how is the myelin sheath formed?
- 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
