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Histology > Nucleus & Cytoskeleton > Flashcards

Nucleus & Cytoskeleton Flashcards

1
Q

Chromatin

A

Genetic material that contains DNA assoc. w/ nuclear proteins

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2
Q

Is chromatin acid or basophilic?

A

Basophilic

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3
Q

Euchromatin

A

Loosely packed, pale staining, active chromatin where majority of transcribed genes are located

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4
Q

Marginal chromatin

A

Heterochromatin at periphery of nucleus near nuclear envelope

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5
Q

Karyosomes

A

Heterochromatin in discrete bodies suspended in nucleoplasm

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6
Q

Amount of euchromatin is proportional to ___

A

Metabolic activity of cell

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7
Q

Heterochromatin

A

Tightly coiled, darkened, inactive, classified by location

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8
Q

Nuclear-associated chromatin

A

Heterochromatin associated w/ nucleus

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9
Q

Barr body

A

Inactive, heterochromatic, 1 of 2 X chromosomes in female cells in interphase nucleus

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10
Q

Where are Barr bodies seen?

A

Neutrophils or epithelial cells scraped from inside of cheek

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11
Q

Pyknotic nuclei

A

Condensed, darkly stained nuclei w/ small amt euchromatin

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12
Q

Vesicular

A

Open-faced, pale-staining active nuclei where euchromatin prevails

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13
Q

Euchromatin are _____rich whereas heterochromatin are ___rich

A

Gene-rich, repeat-rich

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14
Q

Nucleolus

A

. Where rRNA synthesis and initial ribosomal assembly is (contains rRNA and proteins)
. Basophilic
. Cells can have multiple

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15
Q

Where are nucleoli well developed?

A

Cells active in protein synthesis

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16
Q

Nuclear envelope

A

. Has outer and inner membrane separated by pernicious space/cisterna

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17
Q

outer layer of nuclear envelope

A

Continuous w/ RER

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18
Q

Inner membrane of nuclear envelope

A

Supported by nuclear lamina

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19
Q

Nuclear lamina components

A

Intermediate filaments (lamins)

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20
Q

Nuclear pores

A

.Openings in nuclear envelope associated w/pore complex

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21
Q

Nuclear pore complex

A

Facilitates and controls highly selective transport between cytoplasm and nucleus

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22
Q

What happens to nuclear envelope in cell division?

A

It is disassembled during division and then rebuilt after division is completed

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23
Q

Laminopathies

A

Diseases link to defect in proteins of nuclear envelope (lamins) affecting skeletal and cardiac muscle, nerves, and adipose tissue

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24
Q

Interphase stages

A

G1, S, G2

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25
Q

G1 in interphase

A

. Time gap between mitosis and DNA replication

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26
Q

G0 state

A

Cell begin to differentiate but don’t progress into S phase, but suspend all cell activity

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27
Q

S phase

A

DNA and chromosome-associated protein synthesis and centriole replication

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28
Q

G2 phase of interphase

A

Gap between DNA replication and mitosis

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29
Q

Can chromosomes be seen in nucleus in interphase?

A

No, seen ass euchromatin and heterochromatin

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30
Q

Mitosis

A

DNA condenses into chromosomes, nuclear envelope and nucleolus disappear

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31
Q

Mitosis figures

A

LM image nuclei w// condensed chromosomes

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32
Q

When are condensed chromosomes visible in LM?

A

Late prophase, metaphase, anaphase, and telophase

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33
Q

Cytoskeleton

A

System of proteins that supports internal cell architecture and adds in movement of organelles and transport of vesicles as well as cell locomotion and sensing

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34
Q

Microtubule characteristics

A

. Hollow tubes of tubulin
. Rapidly row in length or disassemble as tubulin is added or removed
. Form centrioles and mitosis spindle

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35
Q

Microtubule structure

A

. Tubulin dimers form helix w/ 13 molecules in 1 turn

. outer diameter is 24 nm and hollow core is 14 nm

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36
Q

Tubulin structure

A

Protein with Alpha and beta subunits

37
Q

Where are microtubules found?

A

Cytoplasm growing from microtubule organizing center (MTOC) or in cilia, flagella, and growing neuron axons

38
Q

Colchicine

A

Cancer therapy that prevents tubulin polymerization

39
Q

Taxol

A

Cancer therapy that prevents microtubule depolymerization

40
Q

Functions of microtubules

A

. Intracellular vesicular transport
. Movement (cilia/flagella or chromosomes during division)
. Cell elongation and locomotion
. Maintenance of cell shape

41
Q

Centrioles

A

. Paired short (0.2 um) cylinders
. 2 per cell laying right angles to each other in MTOC
. Duplicate before division

42
Q

Centriole structure

A

Cylinders made of 9 triplets of microtubules that run parallel to long axis and are slightly twisted

43
Q

Centriole duplication and location

A

. New centriole formed at right angle next to existing centriole
. Separate and move to opposite cell poles to be center of mitosis spindle formation

44
Q

Centriole functions

A

. MTOC formation
. Mitotic spindle formation during cell division
. Basal body formation of cilia and flagella

45
Q

Basal bodies

A

Structurally similar to centrioles, formed by migrating centrioles after replication to apical cell surface

46
Q

Actin filaments

A

. Also called microfilaments
. 5-7 nm Polymers of actin molecules
. In ALL eukaryotic cells

47
Q

Actin filaments functions

A

. Formation of 3D skeleton w/in cell
. Part of specialized cell junction
. Structural support of microvilli (core and terminal web)
. Cell locomotion
. Associates w/ microtubules to produce outgrowths of neuronal cell processes

48
Q

Intermediate filaments

A

. 10-12 nm, structural role
. More stable than microtubules and actin filaments
. Absorbs mechanical stress

49
Q

Intermediate filament structure

A

. Assemble from subunits

. High degree of heterogeneity and tissue specificity

50
Q

Types of intermediate filaments

A

Keratin, lamins, vimentin, Desmond, and a family of neurofilaments

51
Q

Clinical significance of intermediate filaments

A

Antibodies to specific intermediate filaments useful in defining origins of metastatic cancer cells

52
Q

Cell junctions

A

. How cells are connected to each other and attached to extra cellular matrix (ECM)
. Facilitate adhesion and communication btw cells

53
Q

Cell adhesion molecules (CAMs)

A

Enable cells to attach to one another and ECM

54
Q

Where are cell junctions prominent?

A

Epithelial cells

55
Q

Types of cell junctions

A

Tight/occluding, adherent, intermediate, desmosomes, and hemidesmosomes

56
Q

Zonulae occludens

A

. Tight junctions
. Cell membranes of adjacent cells come together at regular intervals to seal apical intercellular space
. Surround entire surface of cell (belt-like)
. Assoc. w/ actin filaments

57
Q

CAMs in tight junction formation

A

Occluding and Claudin (transmembrane)

58
Q

Adherent/anchoring junctions

A

Types of cell junction

59
Q

Zonulae adherens

A 
. Intermediate junctions
. Surround entire cells
Intercellular space is present 
. Found below tight junctions near apicla surface of epithelial cells
. Connected to actin cytoskeleton
60
Q

formation of zonulae adherens

A

E and PCadherin CAMs binds to intracellular catenins to link actin filaments from adjacent cells across apical cytoplasm (TERMINAL WEB)

61
Q

Maculae adherens

A

. Desmosomes
. Spot-like junctions
. Disc structures at lateral surface of cells
. In epithelial and cardiacs muscle cells
. Intercellular space present

62
Q

Maculae adherens formation

A

Desmoglein and desmocollin CAMs bind to intracellular attachment plaque that binds to intermediate filaments

63
Q

What is attachment plaque used by desmosome CAMS made up of?

A

Plakoglobin and desmoplakin

64
Q

Keratin filaments

A

Also called tonofilaments, intermediate filaments of epithelial cells

65
Q

Hemidesmosomes

A

. Unilateral junctions anchoring basal domain of epithelial cel to ECM
. Assoc. w/ keratin intermediate filaments

66
Q

Gap junctions

A

. Allow direct communication between adjacent cells via diffusion
. Prominent in epithelia, smooth and cardiac muscle, neural and bone cells\\\\\\\\\\\\\

67
Q

Gap junction formation

A

. 6 connexin monomers form connexon
. 2 connexons from adjacent cells align to form channel
. Connexons form large clusters

68
Q

What opens and closes gap junctions?

A

Conformational changes in connexins

69
Q

Connexin

A

Integral membrane proteins

70
Q

Connexon

A

. Hollow cyndrical hemichannel that spans plasma membrane

. Composed of 6 connexins

71
Q

T/F ALL channels in connexon clusters are active

A

F, as few as 20% can be active

72
Q

Where are connexins NOT expressed?

A

Sperm and adult skeletal muscle

73
Q

Gap junctions are important in tissues involved in _____

A

. Early embryonic development
. Myocardial electrical and contractile activity
. Smooth muscle contraction

74
Q

Blistering diseases are often caused by ____

A

Abnormal desmosome function

75
Q

Mutations in connexin genes are assoc. w/ ____

A

Deafness, congenital cataracts, demyelinating neuropathies, and skeletal defects

76
Q

Apoptosis

A

. Programmed cell death eliminating defective or no longer needed cells
. Not associated w/ inflammation

77
Q

how is apoptosis controlled?

A

. Bcl-2 protein family

78
Q

Apoptosis process

A

. Cytochrome c released from mitochrondria into cytoplasm after signal activating caspases to take apart cells
. Cell and nucleus shrink (pyknotic)
. Fragment into apoptotic bodies (membrane-enclosed) removed via phagocytosis

79
Q

Cascades

A

Proteolytic enzymes that take apart cell content

80
Q

Necrosis

A

. Nonphysiologic process as result of cell injury
. Cell swelling and lysis
. Assoc. w/ inflammation and tissue damage

81
Q

Constitutive heterochromatin

A

Repetitive, gene poor DNA (centromeres and telomeres)

82
Q

Facultative heterochromatin

A

DNA with genes variably inactivated (BARR BODY)

83
Q

Hutchinson-Guilford Progeria Syndrome (HGPS)

A

. Accelerated aging
. Growth failure, skin aging, joint stiffness, stroke
. From Lamin mutation

84
Q

Kinesin function

A

From cell body outside (anterograde) transport

85
Q

Dyeins function

A

Retrograde (back into cell) transport

86
Q

Vimentin

A

Intermediate filaments in fibroblasts

87
Q

Desmin

A

Intermediate filaments in striated muscle

88
Q

Terminal bar

A

Junction made up of zonula occludens, zonula adherens, and macula adherens

89
Q

Epithelial neoplasia

A

. Down regulation of E-cadherin in zonula adherens
. Loss of cell-cell adhesion and cell polarity
. Migratory cells that normally don’t migrate

Histology (22 decks)

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