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BIOL 273 - Principles of Human Physiology 1 > 3.2 - Skeletal Muscle > Flashcards

3.2 - Skeletal Muscle Flashcards

1
Q

What % of the body weight do the skeletal muscles make up?

A

around 40%

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2
Q

What is the function of the skeletal muscles?

A

to position and move the skeleton

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3
Q

Muscles are attached to bones via _____

A

tendons

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4
Q

What are tendons composed of?

A

dense regular connective tissue = collagen

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5
Q

What is collagen?

A

protein arranged into cable-like fibers

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6
Q

What is the outer connective tissue surrounding the whole skeletal muscle?

A

epimysium

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7
Q

What are fascicles?

A

bundles of muscle tissue

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8
Q

Fascicles are covered by a connective tissue sheath called _____

A

perimysium

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9
Q

What are muscle fibers covered by?

A

endomysium

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10
Q

What are myofibrils?

A

functional units of skeletal muscle, contractile and elastic protein bundles

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11
Q

What is the shape of a muscle fiber?

A

long and cylindrical

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12
Q

The cell membrane of a muscle fiber is called the ____

A

sarcolemma

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13
Q

The specialized endoplasmic reticulum of the muscle fiber is called _____

A

sarcoplasmic reticulum

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14
Q

What are T-tubules?

A

transverse tubules

branching tubes associated with the SR

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15
Q

What is the function of the terminal cisternae?

A

sequester Ca2+ with the help of Ca2+ ATPase in SR membrane

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16
Q

What is a triad?

A

1 t-tubules with flanking cisternae

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17
Q

What are the muscle equivalent of these terms?

  • muscle cell
  • cell membrane
  • cytoplasm
  • modified endoplasmic reticulum
A
  • muscle fiber
  • sarcolemma
  • sarcoplasm
  • SR
18
Q

What structures occupy most space in the muscle fiber?

A

contractile structures of the myofibril

19
Q

Myofibrils are made up of proteins. Name the:

  1. Contractile proteins
  2. Regulatory proteins
  3. Accessory proteins
A

contractile proteins:

  • myosin
  • actin

Regulatory proteins:

  • tropomyosin
  • troponin

Accessory proteins:

  • nebulin
  • titin
  • others
20
Q

The repeated patters of striations in a muscle fibre forms a _____

A

sarcomere

21
Q

What is a sarcomere made up of?

A

z-line

I-band = isotropic = reflects light uniformly

A-band = anisotropic = scatters light unevenly

H zone = lighter part of A band

M line = middle

22
Q

What causes these striations?

A

the organization of the protein components of the myofibrils

23
Q

What is the structure of myosin?

A
  • consists of 2 coiled protein chains/mols
  • head and tail region
  • tails are together, heads are at the ends
24
Q

About 250 myosin mols join to form the _____

A

thick filament

25
Q

What are the individual actin subunits called?

A

G-actin (globular)

26
Q

G actin subunits polymerize to form ____

A

F-actin chains

f for filamentous

27
Q

What forms the basis of a thin filament?

A

When 2 F-actin chains twist together

28
Q

The F-actin associates with _____

A

regulatory proteins; troponin and tropomyosin

29
Q

What are known as crossbridges?

A

The direct interaction of myosin heads with actin filaments

30
Q

What forms a completed thin filament?

A

coiled F actin + troponin + tropomyosin

31
Q

The I band contains:

A

ONLY thin filaments

32
Q

TRUE OR FALSE:

The Z-line is the attachment site for ____ and the M-line is the attachment site for ____

A

z-line: thin filaments

m-line: thick filaments

33
Q

The H-zone contains _____

A

only thick filaments

34
Q

How are cross sections taken at the outer edge of an A band lined out?

A

each thin filament is surrounded by 3 thick filaments

6 thin filaments surround 1 think filament

35
Q

Accessory proteins ensure that ____

A

filaments are properly aligned within a sarcomere

36
Q

What is the function of titin?

A
  • stabilizes position of contractile filaments

- returns stretched muscles to their resting length

37
Q

What is titin?

A

largest known elastic protein stretching from z line to m line

38
Q

What is nebulin?

A

non-elastic protein

39
Q

Where does nebulin attach?

A

z disc

40
Q

What is the function of nebulin?

A

helps to align actin filaments in the sarcomere

BIOL 273 - Principles of Human Physiology 1 (24 decks)

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