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Histology > Nervous tissue > Flashcards

Nervous tissue Flashcards

1
Q

nervous system

A

allows rapid and specific communication between widely spaced areas of the body
specialised nerve cells
neurons gather and process information and generate appropriate response signals

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2
Q

2 parts of nervous system

A

central nervous system

peripheral nervous system

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3
Q

CNS

A

brain and spinal cord

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4
Q

PNS

A

nerves running between CNS and other tissues

nerve relay stations - ganglia

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5
Q

neurons functions

A

network of highly specific connections between different groups of cells

gather information from sensory receptors
process information and provide memory
generate appropriate signals to effector cells

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6
Q

what are neurons characterised by?

A

cell body
axon
dendrites
synapses

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7
Q

neuron cell body

A

contains nucleus and most organelles

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8
Q

axon

A

long cell process stretching from cell

transmitting signals from neurons to cells

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9
Q

dendrites

A

numerous short cell processes

increase SA available for connecting with axons of other neurons

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10
Q

synapses

A

specialised cell junctions between axon and other cells to allow direct communication

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11
Q

determination of functional attributes of the nervous system

A

determined by network of connections between neurons, not on specific structural features of individual neurons

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12
Q

neuron activity

A

highly metabolically active

maintain big SA of membrane
energy to develop electrochemical gradients

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13
Q

histological appearance of neurons

A 
large rounded nucleus
large central nucleolus
RER 
Nissl substance - purple stained granules
Golgi
mitochondria
lysosomes
residual bodies containing lipofuscin
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14
Q

Nissl substances

A 
purple stained granules in neurons
cell body (perikaryon) and dendrites, not axon
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15
Q

types of neurons

A

motor neurons
sensory neurons
interneurons

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16
Q

motor neurons

A

large cell body
metabolic support for large axon
many dendritic processes - multipolar neurons

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17
Q

sensory neurons

A

unipolar cells
one major process
divides into 2 branches, one running to CNS and one to sensory area of body

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18
Q

interneurons

A

small, simple cells
short processes providing local connections within CNS
bipolar - 2 main processes of equivalent size, one dendritic and one axonal

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19
Q

intermediate filament of neurons

A

neurofilament protein

acts as internal scaffold to maintain shape of axon and cell body

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20
Q

neurofilaments in axons

A

membrane proteins are anchored in place in organised pattern by attachment to cellular neurofilaments

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21
Q

microtubules in neurons

A

transport substances and organelles up and down axon

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22
Q

metabolic maintenance of long cell process of axon

A

requires transport system for organelles, enzymes and metabolites from cell body

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23
Q

slow axonal transport

A

enzymes and elements of cytoskeleton transported down axon at 1-5mm/day

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24
Q

anterograde fast axonal transport

A

membrane bound organelles transported at speeds of 400 mm/day
mediated by microtubular transport mechanisms using kinesin as motor

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25
Q

retrograde axonal transport

A

effete organelles and recycled membrane from synaptic ending back to neuronal cell body at 300 mm/day
mediated by mechanisms using dynein as motor

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26
Q

how is neuronal signalling controlled?

A

electrical (ionic) gradient across membrane

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27
Q

neuronal firing

A

depolarisation of membrane
resting axon has negative membrane potential (-70mV)
depolarisation is propagated along axon at 100m/s

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28
Q

membrane ion pumps

A

maintain baseline electrical gradient between inside and outside of cell
widely distributed

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29
Q

ion channel proteins

A

modify electrochemical gradient across membrane

form gates/pores which switch permeability to ions in response to specific signals

30
Q

gated channels

A

gates switch permeability to ions in response to specific signals

31
Q

ligand gated channels

A

close or open in response to binding to chemical transmitter substances
synapses

32
Q

voltage gated channels

A

explosive and rapid depolarisation occurring as cells fire

widely distributed in cell membrane

33
Q

depolarisation and small current

A

locally depolarised and small current - no gated channels open
flows down axon by passive local spread for small distance
dissipates due to leakage from membrane

34
Q

depolarisation and large current

A

Na+ and K+ gated channels open and lead to explosive change in membrane potential (action potential)

35
Q

determination of passive local spread

A

resistance and capitance of axon

larger diameter, greater speed

36
Q

synapse

A

special type of cell junction allowing direct communication between cells
transmitter substance secreted in highly localised fashion

37
Q

synaptic bouton

A

terminal end of axon swollen

applied to surface of target cell

38
Q

synaptic cleft

A

20nm gap between synaptic boutons

39
Q

cell membranes on synaptic cleft

A

contain special membrane proteins and receptors involved in neurotransmission

40
Q

ultrastructure of cell membrane on synaptic cleft

A

slightly thickened

synaptic bouton contains mitochondria, microtubules, neurofilaments and neurosecretory vesicles

41
Q

synaptophysin

A

glycoprotein in membrane of neurosecretory granules

42
Q

chromogranins

A

proteins involved in packaging of transmitter into dense core vesicles

43
Q

what does the wave of depolarisation trigger?

A

release of a transmitter substance from neurosecretory granules by exocytosis

transmitter substance diffuses across the synaptic cleft and interacts with receptors in the postsynaptic membrane of target neuron

membrane of vesicle recovered as coated pit and recycles to endosome compartment in the nerve terminal

44
Q

types of neurosecretory vesicles

A

arrive in axon terminal by transport from cell body

formed locally by budding off from endosome compartment in synapse

45
Q

synaptobrevin

A

anchoring protein in membrane of synaptic vesicle

ties vesicle to docking protein in presynaptic membrane (syntaxin) via linking proteins

46
Q

syntaxin

A

docking protein in presynaptic membrane

47
Q

linking proteins

A

SNARE, alphaSNAP, betaSNAP, SNAP25 and NSF

48
Q

membrane fusion proteins

A

in synaptic vesicle membrane and in presynaptic membrane

allow exocytosis

49
Q

synaptotagmin

A

calcium sensitive trigger protein
prevents linking complex from allowing calcium fusion

action potential - voltage sensitive Ca2+ channels open
releases trigger protein, allows exocytosis

50
Q

3 possible effects of a released transmitter binding to receptors on postsynaptic cells

A

depolarisation, hyperpolarisation and altered cell sensitivity

51
Q

depolarisation

A

target cell depolarises if transmitter substance binds to ligand-gated receptor and causes it to open, allowing ions to diffuse into the neuron
if many receptors are activated at once, the alteration in membrane potential causes activation of voltage gated ion channels - action potential

acetylcholine and glutamate

52
Q

hyperpolarisation

A

target cell hyperpolarises if transmitter substance binds to ligand gated receptor admitting small negative ions into cell

inhibits depolarisation

gamma aminobutyric acid
glycine

53
Q

altered sensitivity of the cell

A

transmitter substance binds to a non channel linked receptor
generate secondary messengers (e.g. cAMP) within target neuron to modify overall sensitivity of cell to depolarisation

monoamines
small neuropeptides

54
Q

neuromodulation

A

generating secondary messengers within target neuron to modify overall sensitivity of cell

55
Q

types of synapses

A

axodendritic
axosomatic
axoaxonic
serial axoaxonic

neuromuscular junction - specialised synapse between motor nerve junction and skeletal muscle

56
Q

factors affecting speed of conduction

A

electrical capitance and resistance of axon

increased if leakage of current is minimised by insulation

57
Q

width and capitance

A

wide axons have lower capitance than narrow ones
increasing diameter increases speed of conduction
inefficient as they have high metabolic upkeep

58
Q

myelin

A

produced by oligodendrocytes in CNS and Schwann cells in PNS

lipid rich insulating layer

59
Q

Schwann cell

A

myelinates only one axon

60
Q

oligodendrocyte

A

myelinates several adjacent axons

61
Q

staining of myelin

A

affinity for lipid or protein components of sheath

difference between grey and white matter

62
Q

grey matter

A

neuron rich areas low in myelin

63
Q

white matter

A

tracts of axons with abundant myelin

64
Q

myelin sheath

A

spiral layers of cell membrane around axon

each layer linked to neighbour by cell adhesion proteins

65
Q

formation of myelin sheath

A

begins with invagination of axon into support cells, bringing its outer cell membranes into close opposition and seals them together to form sheet of internal membrane (mesaxon)

66
Q

mesaxon

A

fused outer leaflets of myelin forming cell’s cell membrane

67
Q

intraperiod line

A

line of fusion mediated by proteins in outer surfaces of cell membrane

68
Q

formation of spiral

A

support cell wraps layers of mesaxon around axon
tight spiral composed of double thickness membrane fused together forms - cytoplasm of support cell is excluded from space between layers

69
Q

major dense line

A

inner surfaces of cell membranes fuse together

form dense line

70
Q

lipids in myelin

A

galactocerebroside

71
Q

nodes of Ranvier

A

small bare areas of axon between myelin sheaths

72
Q

where does the cytoplasm of the myelin-forming support cell stay in the myelin sheath?

A

adjacent to axon (inner collar

Histology (10 decks)

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