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

Exam #2: Muscle Flashcards

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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

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

Myomesin

A

Holds the thick filaments to the midline

25
Q

C-protein

A

Holds the thick filaments to the midline

26
Q

Endomysium

A
  • Connective tissue that separates muscle fibers

- Contains Reticular Fibers (Type III Collagen)

27
Q

Perimysium

A
  • Connective tissue that contains bundles of muscle fibers (fasicles)
  • Collagenous
28
Q

Epimysium

A
  • Connective tissue that covers the entire muscle
  • Deep fascia
  • Contains blood vessels & nerve fibers
29
Q

Skeletal Muscle Characteristics

A
  • Multi-nucleated
  • Nuclei pushed to the periphery
  • Fibers oriented longitudinally
  • Euchromatic nucleus (protein synthesis)
  • External lamina is just outside/ small spaces between cells
30
Q

Sarcoplasmic Reticulum

A

Very elaborate sER

31
Q

T-tubules

A
  • 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
Q

Triad

A
  • 2x T-tubules

- Terminal Cisterna

33
Q

Terminal Cisterna

A

Contain Ca++ needed for muscle contraction

34
Q

Motor end-plate

A
  • Nerve terminal on the skeletal muscle fiber

- ACh

35
Q

Motor Unit

A

A single nerve cell & all of the muscle fibers that it innervates

36
Q

Myasthenia Gravis

A

Autoantiboides to AChR on the post-synaptic membrane of a muscle fiber prevent NT binding & cause muscle weakness

37
Q

DMD

A
  • 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
Q

Dystrophin

A
  • Binds actin filaments to laminin

- Mutated (DMD), muscle contraction is inhibited

39
Q

Characteristics of Cardiac Muscle

A
  • Branching
  • Intercalated Discs
  • Large spaces between cells
  • Nuclei at the center of the cell
  • Cells contain 1-2 nuclei
40
Q

What do atrial cardiac muscle cells contain?

A
  • Diuretics enclosed in vesicles
  • Atrial natriuretic peptide & brain natriuretic factor
  • Influence kidney to pump out Na+ & H20 follows
  • Net effect: lower blood pressure
41
Q

Intercalated Discs

A

Function to bind cardiac muscle cells together

42
Q

Transverse Portion vs. Lateral Portion of Intercalated Disc

A

Transverse Portion= Fascia adherens & desmosomes

Lateral Portion= Gap junctions

43
Q

Purkinje Fibers

A
  • Specialized cardiac muscle fibers that are larger than normal
  • Stain paler
  • Fewer myofibrils
  • Contain glycogen
  • Function as “batteries” that relay electrical impulses
44
Q

Characteristics of Smooth Muscle

A
  • NO Sarcomeres
  • Fusiform
  • Euchromatic Nucleus
  • Very little extracellular space
45
Q

What is the function of longitudinally oriented smooth muscle fibers in the GI tract?

A
  • Outer fibers

- Propel luminal contents forward

46
Q

What is the function of circularly oriented smooth muscle fibers in the GI tract?

A
  • Inner fibers

- Decreases the diameter of the lumen

47
Q

Caveole

A

Tiny pinocytotic vesicles associated with smooth muscle that contain & release Ca++ for contraction

48
Q

Dense Bodies

A

Point of contact between myofilaments in smooth muscles

49
Q

How does the morphology of a smooth muscle fiber change with contraction?

A

Contraction causes puckering & a “squishing” of the nucleus

50
Q

What is the effect of ACh binding to the AChR on the post-synpatic sarcolemma?

A

Increases the permeability to Na+

51
Q

How does the nerve impulse spread to the muscle cell?

A

T-tubules

52
Q

What specifically releases Ca++ in the muscle cell in response to a nerve impulse reaching the T-tubule?

A
  • T-tubule interaction with the sarcoplasmic reticulum
  • Sarcoplasmic reticulum contains calciquestrin that contains Ca++
  • Nerve impulse causes calciquestrin to release Ca++
53
Q

What happens when Ca++ is released by Calciquestrin into the cytoplasm?

A

Binds TnC, which induces a conformational change in Troponin

54
Q

What happens once there is a conformational change in Troponin?

A

TnT pushes Tropomyosin deeper into the actin spiral groove, exposing myosin binding sites

55
Q

Describe the actin-myosin cross-bridge cycle.

A

1) Myosin binds actin filaments

2) ATP hydrolysis causes a conformational change in Myosin that pull the actin filament over the thick filament

56
Q

Which band does not change length during muscle contraction?

A

A-band

57
Q

M-line

A
  • 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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