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neuro lectures > neurones and all that > Flashcards

neurones and all that Flashcards

1
Q

what are the basic cellular unit of the nervous system

A

neurones

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2
Q

what are the basic components that all neurones have (4)

A
  • Dendrites
  • Cell body/soma
  • Axon
  • Presynaptic terminal
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3
Q

what are the cell types of the CNS

A

neurones

differentiated glia

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4
Q

how much of CNS cells are accounted for by neurones

A

half - rest are glial cells

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5
Q

what are neurones specialised for

A

electrical signalling

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6
Q

how do neurones receive inputs

A

via dendrites which transmit
to the cell body (soma)

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7
Q

how do neurones transmit info

A

via axons and action potentials are propagated from the axon
hilock

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8
Q

when are neurones mainly formed

A

during development

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9
Q

how do neurones look with H&E stain

A

haemotoxylin - it stains nucleic acid blue

eosin - stains proteins red

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10
Q

which stain stains myelin

A

Luxor fast blue (LFB)

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11
Q

which stain stains stains Nissl (RER)

A

Cresol violet (CV

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12
Q

how do neurones communicate

A

via synapses
2 types

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13
Q

what are the 2 types of synapses

A

chemical and electrical

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14
Q

what are chemical synapses

A

the main type
via neurotransmitters

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15
Q

what are electrical synapses

A

less abundant
via direct flow of ions
enable synchronised electrical activity

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16
Q

examples of electrical synapses

A
  1. brainstem - breathing
  2. hypothalamus - hormone secretion
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17
Q

where are excitatory synapses often concentrated

A

on dendritic spines

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18
Q

describe chemical synaptic transmission

A
  1. axon potential depolarises synaptic terminal membrane
  2. opening of voltage gated calcium channels leads to calcium influx
  3. calcium influx triggers neurotransmitter release
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19
Q

neural plasticity

A

changes in neuronal/synaptic structyre and function in response to neural activity

basis of learning and memory

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20
Q

why is spine remodelling important

A

linked to neural activity

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21
Q

how do neurones differ

A

size
morphology
neurotransmitter content
electrical properties

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22
Q

where are glial cells found

A

surround the soma (cell body), axon and dendrites of neurones

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23
Q

what do glial cells provide

A

they provide neurones with physical & metabolic support

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24
Q

what are the 5 types of glial cells

A
  1. oligodendrocytes
  2. Schwann cells
  3. astrocytes
  4. microglia
  5. ependymal cells
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25
Q

what are oligodendrocytes

A

the myelinating cells of the CNS
unique to vertebrates

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26
Q

function of myelin

A

to insulate axon segments to increase the speed of conduction along the axon

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27
Q

what are myelin sheath segments interrupted by

A

nodes of ranvier - saltatory conduction

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28
Q

are myelinated axons thicker or thinner than normal

A

thicker

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29
Q

where are myelinated axons mostly found

A

in somatic nerves i.e. in fast
sensory/motor systems e.g. muscle & spinal systems

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30
Q

where are unmyelinated axons usually found

A

d in post-ganglionic autonomic
fibres, fine sensory fibres, olfactory neurones & interneurons - essentially where speed is not necessary e.g. hypothalamus (hormonal)

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31
Q

what are nodes of ranvier

A

the spaces between adjacent
sections of myelin where the
axons plasma membrane is
exposed to extracellular fluid

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32
Q

what do oligodendrocytes provide

A

metabolic support for axons in CNS - they are able to transport
metabolic products directly into axons

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33
Q

describe myelin sheath

A

formed by wrapping of axons by 20 - 200 layers of highly moligodendrocyte processes (membranes)
highly compacted - 70% lipid, 30% protein
myelin specific proteins eg myelin basic protein can be used as ‘markers’

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34
Q

how many axons can each oligodendrocyte myelinate

A

each oligodendrocyte may branch to form myelin on as many as 40 axons

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35
Q

what are microglia

A

specialised macrophage-like cells that perform immune functions in the
CNS

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36
Q

what do microglia originate from

A

from yolk sac progenitors that migrate into CNS

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37
Q

where do microglia proliferate

A

at sites of injury and then migrate to sites of damage - phagocytic

38
Q

what are microglia like in the cortical grey matter

A

they are more ramified (branched)

39
Q

how can microglia be bad

A

by being too sensitive causing excessive inflammation & destruction of dendritic spines

40
Q

how do microglia contribute to synaptic plasticity

A

they “eat” unwanted dendritic spines

41
Q

functions of microglia

A

immune surveillance
phagocytosis - debris/microbes
synaptic plasticity - pruning of spines
good (m2 ) and bad (m1) microglia

42
Q

what are astrocytes

A

star like cells
most numerous glial cells in the CNS
highly heterogenous - not all star shaped
common “marker” GFAP

43
Q

sub types of astrocytes

A

protoplasmic - found in grey matter

fibrous - found in white matter

44
Q

astrocyte functions

A
  1. help regulate the composition of the extracellular fluid in the CNS by
    removing K+ ions & neurotransmitters (e.g. glutamate) around synapses
  2. take up glutamate then convert it to glutamine and release it,
    then neurones can take it up and convert it back to glutamate for reuse
  3. stimulate the formation of tight junctions between the cells
    that make up the walls of capillaries found in the CNS - this forms the
    BLOOD-BRAIN BARRIER, which is a much more selective filter for
    exchanged substances that is present between the blood and most other
    tissues
  4. help form the blood-brain barrier by foot-processes closely applied
    around capillaries
  5. sustain the neurones metabolically e.g. by providing glucose
    and removing ammonia
45
Q

specialised astrocytes

A

radial glia - important for brain development

bergmanm glia- found in the cerebellum, support purkinje cell
dendrites & synapses

muller cells - specialised radial glia of the retina

46
Q

function of ependymal cells

A
  • line fluid-filled cavities within the brain (i.e. ventricles) and spinal cord
  • regulate the production & flow of cerebrospinal fluid (CSF)
  • provides barrier between CSF & brain to allow solute exchange between nervous tissue and CSF
47
Q

structure of ependymal cells

A

have cilia, microvilli & desmosomes

48
Q

motor neurones disease

A

adult-onset neurodegenerative disease characterised by loss of upper and lower motor neurones

49
Q

multiple sclerosis

A

autoimmune demyelinating disease where immune cells attack the myelin sheath of oligodendrocytes

50
Q

what is an early marker of Alzheimers

A

the loss of dendritic spines

51
Q

what are the 3 functional classes neurones are grouped into

A
  1. afferent (sensory)
  2. efferent (motor)
  3. interneurons (within the CNS
52
Q

what forms the nerves of the PNS

A

groups of afferent & efferent neurone axons together with connective tissue and blood vessels

53
Q

what does nerve fibre refer to

A

a single axon

54
Q

what does nerve refer to

A

a bundle of axons (fibers) bound
together by connective tissue

55
Q

function of afferent (sensory) neurones

A

convey information from tissues and organs TOWARDS the CNS

56
Q

what do afferent neurones have at their peripheral ends (farthest from CNS)

A

sensory receptors which respond to various physical or chemical changes in their environment by generating electrical signals in the neurone

57
Q

describe shape of afferent neurones

A

shortly after leaving the cell body, the
axon divides;
1. one branch (the peripheral process) begins where the dendritic
branches converge from the receptor endings
2. the other branch (the central
process), enters the CNS to from junctions with other neurons
the cell body & long axon (peripheral process) are OUTSIDE the CNS, and
only a part of the central process enters the brain or spinal cord

58
Q

function of efferent (motor) neurones

A

convey information AWAY from the CNS to effector cells such as muscle,
gland or other cell types

59
Q

structure of efferent neurones

A

cell bodies & dendrites are WITHIN the CNS, and the axons extend OUT to
the periphery

60
Q

function of interneurones

A

connect neurons WITHIN the CNS - form the majority of neurons

61
Q

where are interneurons found

A

they lie entirely WITHIN the CNS

62
Q

which cells form myelin sheath in PNS

A

schwann cells - form individual
myelin sheaths surrounding 1 to
1.5 mm-long segments at
regular intervals along the
axons

63
Q

where are myelinated axons mostly found

A

in somatic nerves i.e. in fast
sensory/motor systems e.g. muscle & spinal systems

64
Q

difference between schwann cells and oligodendrocytes

A

schwann - myelinate PNS
myleinate single axon

oligodendrocytes - myelinate CNS
myelinate multiple axons

65
Q

what causes epilepsy

A

disease of neurones

66
Q

what causes depression

A

disease of neurones and glia

67
Q

what are tracts

A

a collection of nerve fibers (axons) in the CNS

68
Q

what is contained in nuclei in CNS

A

abundance of neuronal cell bodies

69
Q

what are commissures

A

tracts that cross midline in the CNS

70
Q

what is neuropil

A

the dense network of fine glial processes, neuronal processes (axons and dendrites), and fibrils in the gray matter of CNS

71
Q

where are cell bodies and supporting cells located in the PNS

A

ganglia

72
Q

what are axons bundled into in the PNS

A

nerves

73
Q

what is the blood brain barrier (BBB)

A

A network of blood vessels and tissue that is made up of closely spaced cells and helps keep harmful substances from reaching the brain

74
Q

what is BBB formed from (3)

A
  • endothelial cells
  • pericytes (contractile cells that wrap around the endothelial cells of capillaries and venules)
  • astrocytes
75
Q

features of BBB (5)

A
  • Endothelial tight junctions
  • Astrocyte end feet
  • Pericytes
  • Continuous basement membrane, lacks fenestrations (windows)
  • Requires specific transported for glucose, essential ions etc
76
Q

what are CIRCUMVENTRULAR ORGANS

A

certain parts of the brin that lack the BBB

77
Q

example of a circumventrular organ

A

posterior pituitary - they need to be in
contact with the blood for a sensory role to monitor

78
Q

what is BBB sensitive to

A
  • inflammation
  • hypertension
  • trauma
  • ischaemia
79
Q

where does CSF circulate

A

through the subarachnoid space (around the brain and spinal cord)
and within ventricles - offers protection by cushioning brain from gentle
movements)

80
Q

what does CSF do

A

offers protection by cushioning brain from gentle movements

81
Q

what are the 4 ventricles

A
  1. Lateral (paired)
  2. III
  3. IV
82
Q

how do ventricles & subarachnoid
spaces connect

A

via cisterns

83
Q

describe CSF appearance

A

a clear, colourless liquid

84
Q

what does CSF contain

A

protein, urea, glucose & salts

85
Q

what is CSF produced by

A

by ependymal cells in the choroid plexuses of the lateral ventricles
(mainly)

86
Q

what is choroid plexus

A

a network of blood vessels in each ventricle of the brain, producing the cerebrospinal fluid.

87
Q

what is choroid plexus formed from

A

from modified ependymal cells

they from around a network of capillaries, large surface area

88
Q

how is CSF absorbed

A

via arachnoid granulations (VILLI) e.g. in the superior sagittal sinus

89
Q

what is hydrocephalus

A

a disease
abnormal accumulation of CSF in ventricular system
often due to a blocked cerebral aqueduct

90
Q

impact of accumulation of CSF

A

leads to a build up of pressure which can damage brain tissue since the skull in hard in adults

  • In children with soft skull the pressure will cause the soul to bulge and look
    abnormal as well as damaging the brain

neuro lectures (15 decks)

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