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Skin MS: Week 2 > Histology (11/6) > Flashcards

Histology (11/6) Flashcards

1
Q

Embryology of Nervous System

A

Neural crest
PNS: sensory neurons of spinal & cranial ganglia; motor neurons of autonomic ganglia; glia of the PNS; other “non-neuronal” cell types

Neural tube
Neurons & glia of CNS

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2
Q

Mitotic potential of NS cells

A

Neurons are non-mitotic

Glial cells maintain mitotic capability

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3
Q

White Matter

A

Aggregations of axons, includes nerves in PNS and tracts, columns, fasciculi of axons in CNS, white d/t myelination

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4
Q

Gray Matter

A

AGgregations of nerve cell bodies + neuropil
Ganglia in PNS, nuclei etc in CNS
Gray d/t little myelin

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5
Q

Neuropil

A

complex network of nerve cell processes, synapses, and glial cells occupying intervals between nerve cell bodies in gray

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6
Q

Constituents of Nervous Tissue: CNS

A

Nerve cells
Glia: Astrocytes, oligodendrocytes, Microglia, ependymal cells
Blood vessels

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7
Q

Constituents of Nervous Tissue: PNS

A

Nerve cells
Glia: Schwann cells, Satellite cells
Blood vessels
connective tisse

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8
Q

General Cytology/Components of Nerve Cell

A

Plasma membrane, cell body, Dendrites, (Sensory receptors), axon, end terminal

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9
Q

RER in nerve cells

A

Nissl bodies

Extensive - present throughout whole cell body + dendrites, absent from axon hillock + axon

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10
Q

Golgi in Neurons

A 
Just in cell body 
Package vesicles (full or empty) to send down axon
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11
Q

Neurofilaments

A

Type of intermediate filament found only in neurons - structural role - form neurofibrils - found in body and processes

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12
Q

Microtubules in neurons

A

Involved in transport of molecules/particles down axon (maybe growth and development)

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13
Q

Microfilaments in neurons

A

Specialized distribution (growth cones, some junctions)

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14
Q

Pigments in Neurons

A

Lipofuscin - insoluble remnants of lysosomes (product of digestion) - golden brown
Neuromelanin - naturally occuring in some areas, dark brown/black

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15
Q

Mitochondria in Neurons

A

Large numbers throughout cells, especially abundant in axons

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16
Q

Unencapsulated nerve endings (receptors)

A

Touch, pain (maybe hot/cold)

i.e. merkel cell (Touch)

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17
Q

Corpuscles of Ruffini + Krause’s end-bulbs

A

mechanoreceptors, glomerular (encapsulated)

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18
Q

Meissner’s Corpuscle

A

Touch
Fibrous capsule (encapsulated)
Found in hairless skin

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19
Q

Pacinian Corpuscle

A

Deep pressure, vibration
Lamellar corpuscle
Looks like onion

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20
Q

ABC grades of axons

A

A - large, myelinated
B - smaller, myelinated
C - smallest, not myelinated

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21
Q

Presynaptic dense projections

A

electron dense material on cytoplasmic side of membrane at axon end terminal
Vesicles approach and fuse with presynaptic membrane (guide into right place)

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22
Q

Axonal Transport : Slow

A

Only orthograde

Carries soluble macromolecules, small molecules not in vesicles, fibrillar components of axoplasm

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23
Q

Axonal Transport: Fast

A

Orthograde faster than retrograde (both much faster than slow), microtubules
Orthograde: vesicles, organelles, etc. - KINESIN –> plus end (faster)
Retrograde: Worn out membranes, etc. - DYNEIN –> minus end

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24
Q

Consequences of Retrograde transport

A

clinically: how viruses (i.e. rabies) get far into nervous system
developmentally: might be how axons are told to grow
experimentally: track process of marker molecules back to find cell bodies

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25
Q

Neuroglia of CNS

A

Astrocytes, Microglia, Oligodendrocytes, Ependymal cells

Outnumber neurons

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26
Q

Macroglia

A

Astrocytes + Oligodendrocytes

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27
Q

Types of Astrocytes

A

Fibrous or Protoplasmic (Golgi staining vs. H&E) - either due to functional states or location

28
Q

Golgi stain appearance of astrocytes

A

Cell body usually obscured by mass of processes, found near blood vessels/surfaces of brain

29
Q

H&E/Nissl Stain Astrocytes

A

Nucleus - oval, large

30
Q

Functions of Astrocytes

A

Terminal end feet –> pervasive between neurons and processes –>
End on blood vessels (maybe induce blood brain barrier)
End on inner surface of pia mater - external glial limiting membrane
End on basal surface of ependymal cells to form internal glial limiting membrane

Structural support, uptake potassium after activity, phagocytosis, Isolation from other neurons, regulation of environment

31
Q

Appearance of Oligodendrocytes

A

Fewer processes than astrocytes

Nucleus (Nissl stain) - round, smaller, dense staining

32
Q

Functions of oligodendrocytes

A

Myelination of CNS axons, maybe nutritive/maintenance

33
Q

Microglia

A

5% or less of all glial cells, derived from monocytes - actively phagocytic

34
Q

Ependymal cells

A

Line central canal of spinal cord, ventricles of brain
Simple cuboidal, columnar epithelial - ciliated
Beat CSF to brain, secretion into ventricles
Modified to be choroidal epithelium - control composition of CSF in ventricles of brain

35
Q

Epineurium

A

External layer, tough, dense collagen

36
Q

Perineurium

A

Envelopes bundles or fascicles of fibers
Intermediate in character between epi and endoneurium
inner aspect has epithelioid like cells

37
Q

Endoneurium

A

around individual axons
delicate collagen
contacts basement membrane of schwann cells which cover axon

38
Q

Unmyelinated fibers of PNS consist of ____

A

Axon + Sheath of Shwann

39
Q

Development of Sheath of Schwann

A

Schwann cells from neural crest - travel along axons
Each SC embraces a small number of axons
Trough, remain outside even though engulfed

40
Q

Function of Sheath of Schwann in unmyelinated axons

A

unknown

41
Q

Mesaxon

A

region where lips of schwann cell cytoplasm meet (gap)

42
Q

Bundle of Remak

A

Collective term for a group of unmyelinated fibers encompassed by single schwann cell

43
Q

c fibers

A

term for unmyelinated axons
axons of most post-ganglionic autonomic neurons
axons of small sensory neurons in Dorsal root ganglia
Not usually seen d/t not stained

44
Q

Myelinated fibers of PNS

A

Axon, myelin, sheath of schwann

Largest axons have thickest myelin, fastest conducting

45
Q

Myelin content

A

High lipid content (protein)

46
Q

Appearance of myelin

A

Fresh: white d/t lipids
Osmium stained: Black empty rings
H&E: see the residual protein (neurokeratin)
EM: Black

47
Q

Nodes of Ranvier

A

Periodic breaks in myelin sheath
space between adjacent schwann cells
Highest conc. Na channels

48
Q

schmidt lantermann clefts

A

oblique clefts in myelin, faults in smooth wrapping myelin lamellae, light areas = trapped portions of schwann cell cytoplasm

49
Q

Myelination via Jelly-roll theory

A

Myelin formed by spiral wrapping of SC membrane around nerve fiber
Cytoplasm of SC squeezed out –> compaction –> intraperior and major dense lines
Nucleus of SC in cytoplasm of final wrap

50
Q

Intraperiod Line

A

former outer surfaces of schwann cell – fuse to become very thin

51
Q

Major dense line

A

Former cytoplasmic surfaces of schwann cell

52
Q

Internal and external mesaxons

A

regions where schwann cell meets itself as it encircles axon initially (internal) and where it overlaps on last turn (external)

53
Q

Myelinated Fibers of CNS

A

Oligodendrocytes responsible for myelination, may myelinated more than one axon = little cytoplasm, never a nucleus near axon (remain distant, tongue)

54
Q

Nodes of Ranvier in PNS

A

Cytoplasm of Schwann cell covers, basement membrane out SC inside endoneurium
Collateral branches, en passage synapses occur

55
Q

Nodes of Ranvier in CNS

A 
Shorter internodal distance
Node exposed to extracellular space 
No basement membrane outside myeline
No SL clefts
No Connective tissue
56
Q

Sensory Ganglia (PNS)

A 
Light and dark cells
No synapses in ganglia
Satellite cells (capsule cells)
Fibroblasts
C.t. capsule
Nuclei in middle of cells

Dorsal root ganglia and cranial nerve ganglia

57
Q

Satellite Cells

A

Very small cells which form covering around each ganglion neuron, may be schwann cells, may play role in metabolism of ganglion neurons

peripheral glia

58
Q

Connective tissue capsule (PNS ganglia)

A

surround entire ganglia, continuous with perineurium/epineurium, extend into ganglion to separate nerve cell bodies into groups

59
Q

Autonomic ganglia

A

Synapses
Pre - Type B (myelinated)
Post - Type C (small, not myelinated)
Satellite cells and schwann cells

60
Q

Wallerian or Orthograde Degeneration

A

Portion of axon separated from cell body changes
Axon/terminals/myelin disintegrate
Schwann cell + CT remain in PNS (none in CNS)
Phagocytosis of debris

61
Q

Retrograde Degeneration

A

Changes in cell body/portion of axon still attached
Degeneration for short time toward cell body
Chromatolysis (cell body/nucleus swell, moves to side, RER disintegrate)
Death of cell with or without chromatolysis MAYBE
Or maybe no change at all

62
Q

Regeneration

A

Successful only in PNS
Multiple sprouts emerge from central stump of axon –> one must get through surviving tube of schwann cells
Remyelination

63
Q

Specificity of Reinnervation

A

Will innvervate any sensory receptor/muscle - sensation/motions less critical

64
Q

Traumatic neuroma

A

Large heterogeneous mass of entangled nerve fibers, schwann cells, ct cells, etc
Regen. neurons unable to overcome obstacle
Afferents may still send messages –> painful

65
Q

CNS regeneration

A

Abortive
No guiding tube (oligodendrocytes)
Scar tissue by astroglia barrier

66
Q

Plasticity

A

REcovery after CNS injury

Collateral sprouting - new connections OR unmasking of other connections

Skin MS: Week 2 (12 decks)

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