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CNS > Unit 2-embryology and histology of nervous system > Flashcards

Unit 2-embryology and histology of nervous system Flashcards

1
Q

What structures are apparent at week 4 of embryological development?

A

Neural crest and tube

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2
Q

What do the neural crest and tube become?

A

The spinal cord and 3 primary brain vesicles (which has two flexures: cervical and cephalic)

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3
Q

What are the 3 primary brain vesicles?

A

The prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain)

these 3 vesicles are primary vesicles

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4
Q

During weeks 5-6 what does the prosencephalon develop into?

A

the telencephalon and diencephalon

secondary vesicles

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5
Q

what structures come from the telencephalon?

A

cerebral cortex, basal ganglia, and lateral ventricles

secondary vesicles

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6
Q

what structures come from the diencephalon?

A

thalamus, hypothalamus, pineal gland, and 3rd ventricle

secondary vesicles

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7
Q

During weeks 5-6 what does the mesencephalon develop into?

A

corpora quadrigemina (tectum), cerebral peduncles, and cerebral aqueduct

secondary vesicles

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8
Q

during weeks 5-6 what does the rhombencephalon develop into?

A

the metencephalon and myelencephalon

secondary vesicles

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9
Q

what structures come from the metencephalon?

A

cerebellum, pons, and 4th ventricle

secondary vesicles

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10
Q

what structures come from the myelencephalon?

A

M.O., and 4th ventricle which is continuous with the spinal cord

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11
Q

The brain at birth equals what percentage of body weight and uses how much O2?

A

10% and uses 50-60% of O2

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12
Q

As an adult the brain equals what percentage of body weight and uses how much O2?

A

2-5% and uses 20% of O2

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13
Q

Within 1st year how much in size does the brain grow?

A

it doubles it size and more then 1/2 of brain growth occurs during this time period

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14
Q

The CNS arises from what structure in general?

A

the neural tube

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15
Q

The PNS arises from what structs in general?

A

the neural crest cells

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16
Q

Neuroepithelial cells give rise to what structes?

A

Neuroblasts, ependymal cells, and glioblasts

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17
Q

Neuroblasts give rise to what?

A

neurons

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18
Q

Glioblasts give rise to what?

A

astrocytes and oligodendrocytes

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19
Q

Gliobasts are synonymous with what and can undergo what?

A

nerve glue

they can undergo mitosis

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20
Q

What are some functions of glioblasts?

A

their derivations are the FUNCTIONAL connective tissue of the CNS and help guide neurons to their positions in early development

there are 5-10x as many glioblast derivatives as there are neurons

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21
Q

Astrocytes characterisitcs

A

most numerous cell in adult nervous sytem’

have mobility potential

little evidence to suggest they divided in mature brain

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22
Q

Protoplasmic astrocytes are found where?

A

in gray matter

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23
Q

Fibrous astrocytes are found where?

A

in white matter

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24
Q

Functions of astrocytes

A

structural support cells

found between blood vessel capillaries and neuron cell bodies as part of the BBB

stores what little glucose can be stored in the nervous system

forms “scar-like” tissue in CNS after injury

neurotransmitters like dopamine, glutamate, and serotonin may be influenced by astrocytes at synatpic gaps

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25
Q

Oligodendrocyte characteristics

A

fewer in number than astrocytes and mainly forms myelin sheaths

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26
Q

Perineuronal satellites (type of oligodendrocyte)

A

found in gray matter and has possible nutritional role

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27
Q

Interfasicular (type of oligodendrocyte)

A

found in white matter and forms myelin in CNS

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28
Q

Characteristics of ependymal cells

A

line the central canal and ventricles

serve as leaky barrier between CSF and CNS parenchyma

classified as simple cuboidal but some are adapted taller cells and with microvilli and are present in ventricles

secretes CSF from choroid plexus in each ventricle

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29
Q

found in 3rd ventricle and transports CSF to hypophyseal portal system

A

tanycytes

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30
Q

most common primary brain tumor

A

astrocytoma

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31
Q

most lethal brain tumor and is more likely to occur as one is older

A

glioblastoma

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32
Q

derived from ependymal cells and dysfunctions CSF which accumulates CSF in brain

A

ependyoma

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33
Q

Microglio characteristics

A

Mesodermally derived and arise from fetal macrophages which sequester into blood stream during development

while resting they have numerous tiny processes

they become activated after neural tissue is injured and become phagocytic, clearing damaged or dead tissue

mediates CNS immune responses

only neural cells affected by HIV

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34
Q

Neuralblast chracterictics

A

neuroepithelial origins near neural tube

show little mitotic ability

depend glial cells to guide them as they move through CNS

radiation or alcohol exposure during development may cause them over/under shoot their destination

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35
Q

(pseudo)unipolar neuron

A

most common; found in DRG or spinal ganglion

really two neurons wrapped together to look like one

primarily used for sensory function and found in PNS as afferent neuron

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36
Q

bipolar neuron

A

found dominately in special sense organs such as retina, inner ear, and nasal cavity

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37
Q

multipolar neuron

A

has only one axon but many dendrites and branches

is the vast majority of neurons in CNS and is most numerous

carries motor information

38
Q

Golgi type I (multipolar)

A

has a long axon maybe 1M or longer

39
Q

Golgi type II (multipolar)

A

short axons and more numerous than golgi type I

40
Q

sensory neruon

A

afferent

runs from PNS to CNS

neural crest derivative

41
Q

motor neruon

A

efferent

runs from CNS to PNS

neural tube derivative

42
Q

Internuncial neuron

A

only in CNS

messengers or connectors between incoming sensory info and outgoing motor

associative or interneuron are interchangeable with internuncial

43
Q

commissural neuron

A

neuron that runs between equal structures on opposite sides of CNS

Ex. Lt. central gyrus to Rt. central gyrus

44
Q

Projection neuron

A

type of internuncial that runs from one structure in the CNS and ends in another struture

Ex. Rt. cerebrum to Lt. midbrain

45
Q

Ipsilateral

A

runs on the same side

46
Q

Contralateral

A

runs on opposite side

47
Q

Intra segmental

A

begins and ends in the same cord level

48
Q

inter segmental

A

begins in one cord level and ends in another

49
Q

Cell body (some, or perikaryon)

A

contains the nucleus of a neuron

50
Q

Axon hillock

A

gradually boundary between the axon and cell body

this is where nerve or action potentials are initiated

51
Q

Axolemma

A

outer plasma membrane of neuron

52
Q

Typical diameter of a perikaryon?

A

4-130 microns, the bigger the perikaryon the faster a nerve impulse travels

53
Q

The shapes of a perikaryon?

A

stellate, fusiform, oval, round, and pyramidal

54
Q

how long can a process be?

A

from just a few microns up to 40 inches

55
Q

Axoaxonic

A

least common form of a synapse

the end of an axon from one neuron synapses onto the axon of another neuron

56
Q

axodendritic

A

most common form of a synapse

the axon of one neuron synapses onto the dendrite of another neuron

57
Q

axosomatic

A

the axon of one neuron synapses onto the cell body of another neuron

58
Q

organelle that is considered the powerhouse is most concentrated where in the cell and produces what compound?

A

the mitochondria and is concentrated in the cell body and telodendria due to high levels of activity

the mtiochondria produces ATP

59
Q

the golgi apparatus houses what processes?

A

retispersion and chromatolysis

60
Q

retispersion is the process of what?

A

fragmentation of the golgi apparatus

61
Q

chromatolysis is the process of what?

A

Nissl bodies are dispersed after neuronal injury

62
Q

what are nissl bodies and what other name do they go by?

A

clumps of RER and free ribosomes plus iron deposits

they are also called tigroid bodies

nissl bodies only appear in large neurons and are only found in the cell body and dendrites of neurons

63
Q

centrosome organelle

A

likely the remnants of when it was capable of mitosis

64
Q

Are neurofibrils real?

A

yes they are

65
Q

List the three types of microfibrils

A

microtubules

microfilaments

neurofilaments

66
Q

What is the function of microtubules and their size?

A

They help maintain cell shape and are 20-30nm in diameter

67
Q

What is the function of microfilaments and their size?

A

they run longitudinally and circumferentially and associate with axolemma. theyre 3-5nm is diameter

68
Q

How big are neurofilaments?

A

9-10 nm in diameter

69
Q

Describe axoplasmic transport

A

it is the movement of raw materials within a cell

70
Q

Describe slow transport in a cell

A

its the movement of materials like protein for neurofibrils and mitochondira within a cell

moves about .1-3 mm/day in the anterograde direction

speed of flow depends on axon length; the longer the faster; also needs little energy

71
Q

Describe fast transport

A

is the movement of synaptic vessicles,lysosomes, and enzymes

moves 100-400 mm/day anterograde or retrograde

speed of transport not dependent on axon length but needs energy

72
Q

What is the myelin covering in the CNS?

A

intrafasicular oligodendrocytes

73
Q

What is the composition of myelin?

A

phospholipid/cholesterol and neurokeratin

74
Q

Is myelin made by the neuron?

A

No its made by a surrounding cell

75
Q

What forms the myelin in the PNS?

A

Schwaan cells

76
Q

What part of the neuron does myelin only cover?

A

the long axon process

77
Q

How long must a neuron fiber be for myelin to form on it?

A

at least one micron in length

78
Q

If the neuron fiber is thicker, in general whats the diameter of the myelin?

A

its thicker as well

79
Q

Is a nerve impulse faster if the myelin is thicker or thinner?

A

if the myelin is thicker

80
Q

What two things determine conduction velocity?

A

fiber diameter and myelin

81
Q

What would be an example of a PNS nerve fiber that has a schaan cell but is not myelinated?

A

post ganglion sympathetic neurons

82
Q

What is it called when one schwaan cell in the PNS meets another schwaan cell?

A

node of ranvier

83
Q

What is an internode?

A

the length of a schwaan cell covering

84
Q

How long can an internode be?

A

50-750 microns

85
Q

Do all nerve fibers have a neurilemma?

A

yes

86
Q

Describe endoneurium

A

highly vascular, fibrous and cellular matrix covering neurilemma. continues onto telodendritic branches

87
Q

Describe perineurium

A

it wraps around groups of fibers

it is the most elastic of coverings

its continuous with the pia and arachnoid as it gets close to CNS structures

88
Q

Describe epineurium

A

outer coat of a nerve

inelastic, gives protection, strength and support to fibers.

is continuous with dura as it gets close to CNS structures

89
Q

Are nodes of ranvier in the CNS?

A

yes but are oligodendrocytes instead

90
Q

How many cells can an oligodendrocyte cover?

A

up to 40

CNS (7 decks)

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