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Cell & Tissue Biology > Exam #2: Muscle > Flashcards

Exam #2: Muscle Flashcards

(57 cards)

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1
Q

Sarcomere

A

Contractile unit of muscle

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2
Q

What are the three components of thin filaments?

A

1) Actin
2) Troponin
3) Tropomyosin

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3
Q

Actin

A
  • Globular protein

- Main component of thin filaments

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4
Q

What are the three components of troponin?

A 
TnT= attaches to tropomyosin
TnC= Binds Ca++
TnI= binds actin & inhibits myosin binding
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5
Q

Tropomyosin

A
  • Two polypeptide chains forming an alpha-helix
  • Forms a filament that wraps around actin
  • Block active sites on actin monomers to prevent myosin binding
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6
Q

Filamentous

A

Two twisted polymers of actin

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7
Q

What are thick filament composed of?

A

Myosin II (roughly 200 subunits form a thick filament)

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8
Q

Heavy Meromysin

A
  • 2x globular heads
  • 4x light chains
  • Short twisted tail
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9
Q

Light Meromysin

A

Long twisted tail

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10
Q

Heavy chain

A

Golf club appearing chains

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11
Q

Light chain

A

Golf ball appearing chains

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12
Q

S1

A

Globular head & 2x light chains

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13
Q

S2

A

Short twisted tail

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14
Q

What are the thick bold lines in a sarcomere?

A

Myosin

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15
Q

What are the thin gray lines in a sarcomere?

A

Actin

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16
Q

What are the boundaries of a single sarcomere?

A

Z-disc–> Z-disc

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17
Q

A-band

A
  • Dark band
  • Contains thick & thin filaments
  • Bisected by the H & M bands
  • Widest band of sarcomere
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18
Q

I-Band

A
  • Light band
  • Thin filaments ONLY
  • Formed by 2x adjacent sarcomeres
  • Bisected by the z-disc
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19
Q

Z-disc

A
  • Attachment for thin filaments
  • Contains alpha-actinin
  • Bisects the I-band
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20
Q

H-band

A
  • Thick filaments only

- Bisects the A-band

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21
Q

Alpha-actinin

A
  • Associated with the z-disc

- Anchors the thin filaments to the z-disc

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22
Q

Nebulin

A
  • Associated with the z-disc
  • Non-elastic
  • Holds the thin filaments in place
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23
Q

Titin

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A
  • Associated with the H-band
  • Anchors the thick filaments to the sarcomere (z-dics)
  • Elastic
24
Q

Myomesin

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A

Holds the thick filaments to the midline

25
C-protein
Holds the thick filaments to the midline
26
Endomysium
- Connective tissue that separates muscle fibers | - Contains Reticular Fibers (Type III Collagen)
27
Perimysium
- Connective tissue that contains bundles of muscle fibers (fasicles) - Collagenous
28
Epimysium
- Connective tissue that covers the entire muscle - Deep fascia - Contains blood vessels & nerve fibers
29
Skeletal Muscle Characteristics
- Multi-nucleated - Nuclei pushed to the periphery - Fibers oriented longitudinally - Euchromatic nucleus (protein synthesis) - External lamina is just outside/ small spaces between cells
30
Sarcoplasmic Reticulum
Very elaborate sER
31
T-tubules
- Invaginations of the sarcolemma that contain ECF - Function to carry the nerve impulse to the sarcomere - Run perpendicular to the longitudinal axis of the cell
32
Triad
- 2x T-tubules | - Terminal Cisterna
33
Terminal Cisterna
Contain Ca++ needed for muscle contraction
34
Motor end-plate
- Nerve terminal on the skeletal muscle fiber | - ACh
35
Motor Unit
A single nerve cell & all of the muscle fibers that it innervates
36
Myasthenia Gravis
Autoantiboides to AChR on the post-synaptic membrane of a muscle fiber prevent NT binding & cause muscle weakness
37
DMD
- Duchenne Muscular Dystrophy - Most common & severe form of muscular dystrophy affected striated (muscle & cardiac) muscle - Characterized by weakness of large muscle groups - XP21 locus on the x-chromosome is mutated, which affects synthesis of "dystrophin" protein
38
Dystrophin
- Binds actin filaments to laminin | - Mutated (DMD), muscle contraction is inhibited
39
Characteristics of Cardiac Muscle
- Branching - Intercalated Discs - Large spaces between cells - Nuclei at the center of the cell - Cells contain 1-2 nuclei
40
What do atrial cardiac muscle cells contain?
- Diuretics enclosed in vesicles - Atrial natriuretic peptide & brain natriuretic factor - Influence kidney to pump out Na+ & H20 follows - Net effect: lower blood pressure
41
Intercalated Discs
Function to bind cardiac muscle cells together
42
Transverse Portion vs. Lateral Portion of Intercalated Disc
Transverse Portion= Fascia adherens & desmosomes | Lateral Portion= Gap junctions
43
Purkinje Fibers
- Specialized cardiac muscle fibers that are larger than normal - Stain paler - Fewer myofibrils - Contain glycogen - Function as "batteries" that relay electrical impulses
44
Characteristics of Smooth Muscle
- NO Sarcomeres - Fusiform - Euchromatic Nucleus - Very little extracellular space
45
What is the function of longitudinally oriented smooth muscle fibers in the GI tract?
- Outer fibers | - Propel luminal contents forward
46
What is the function of circularly oriented smooth muscle fibers in the GI tract?
- Inner fibers | - Decreases the diameter of the lumen
47
Caveole
Tiny pinocytotic vesicles associated with smooth muscle that contain & release Ca++ for contraction
48
Dense Bodies
Point of contact between myofilaments in smooth muscles
49
How does the morphology of a smooth muscle fiber change with contraction?
Contraction causes puckering & a "squishing" of the nucleus
50
What is the effect of ACh binding to the AChR on the post-synpatic sarcolemma?
Increases the permeability to Na+
51
How does the nerve impulse spread to the muscle cell?
T-tubules
52
What specifically releases Ca++ in the muscle cell in response to a nerve impulse reaching the T-tubule?
- T-tubule interaction with the sarcoplasmic reticulum - Sarcoplasmic reticulum contains calciquestrin that contains Ca++ - Nerve impulse causes calciquestrin to release Ca++
53
What happens when Ca++ is released by Calciquestrin into the cytoplasm?
Binds TnC, which induces a conformational change in Troponin
54
What happens once there is a conformational change in Troponin?
TnT pushes Tropomyosin deeper into the actin spiral groove, exposing myosin binding sites
55
Describe the actin-myosin cross-bridge cycle.
1) Myosin binds actin filaments | 2) ATP hydrolysis causes a conformational change in Myosin that pull the actin filament over the thick filament
56
Which band does not change length during muscle contraction?
A-band
57
M-line
- Protein structures lying between thick filaments - Creatine Kinase is the major protein - Bisects the H-band

Cell & Tissue Biology (25 decks)

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