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Therapeutic Exercise Year 1 > Structure of Skeletal Muscles > Flashcards

Structure of Skeletal Muscles Flashcards

1
Q

What are the 7 structures of a skeletal muscle?

A
  1. Epimysium.
  2. Perimysium.
  3. Fasiclcle.
  4. Endomysium.
  5. Muscle fiber.
  6. Sarcolemma.
  7. Myofibril.
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2
Q

What is the Epimysium?

A

A connective tissue sheath that -
- Enwraps the entire muscle.
- Enables muscle to retain structural integrity when contracting + lengthening.
- Keeps muscles separate from each other.

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3
Q

What is the Perimysium?

A

A connective tissue sheath that -
- Enwraps the fascicles.
- Allows the nervous system to recruit fibres housed within the fascicle with greater specificity.

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4
Q

What is Fascicle?

A

A bundle of skeletal muscle fibres surrounded by the perimysium.

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5
Q

What is the Endomysium?

A

Connective tissue sheath that -
- Enwraps individual muscle fibres.
- Surrounds + supports the cell’s extracellular matrix.

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6
Q

What is the Muscle Fibre?

A
  • Muscle fibre is composed of many fibrils.
  • Gives the cell its striated appearance.
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7
Q

What percentage of muscle fibre is occupied by water?

A

75%.

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8
Q

What percentage of muscle fibre is occupied by protein?

A

20%.

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9
Q

What 2 proteins make up the 20% of muscle fibre space?

A
  • Myofibrillar (15%)
  • Non myofibrillar (5%)
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10
Q

What are Myofibrillar proteins (15%)?

A
  • Proteins involved in contraction.
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11
Q

What are Non Myofibrillar proteins (5%)?

A
  • Are enzymes.
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12
Q

What is the Sarcolemma?

A
  • Is the cell membrane covering each muscle fibre.
  • Consists of elastic properties.
  • Needs to have elasticity to withstand tensile load + not rupture.
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13
Q

What is the Myofibril?

A
  • Give the fibre its structure and function.
  • Myofibrils are suspended in the sarcoplasm + run the length of the fibre.
  • Are made up sarcomeres connected in series.
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14
Q

Outline the 4 steps on how connective tissue structures permit ‘Force Transmission’ to produce movement.

A
  1. When a muscle contracts tension is created.
  2. Tension is transferred sequentially through each connective tissue layer to the tendon.
  3. Force is concentrated at the myoconnective junction.
  4. Force is transferred to the periosteal layer of the bone, which pulls on it + creates movement.
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15
Q

Where are Nuclei found in a muscle fibre?

A
  • Found at the periphery of the fibre in the space between the myofibrils + sarcolemma.
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16
Q

Where is there a higher Myonuclei density in the muscle fibre?

A

Motor end plate.

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17
Q

Why is it important muscle fibres have multiple nuclei?

A
  • More nuclei support the theory of Hypertrophy.
  • It supplies the muscle with protein allowing it to grow.
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18
Q

Outline the layered structure of the Sarcolemma.

A
  1. Phospholipids.
  2. Membrane-bound receptors + transport molecules.
  3. Structural proteins that anchor the cytoskeleton to the extracellular matrix.
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19
Q

What is the Basement Membrane?

A
  • Found external to the Sarcolemma.
  • Anchors the fibre.
  • Supports cell development + regernation.
  • Helps mechanotransduction to occur.
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20
Q

What is the Basement Membrane also referred to as?

A

Basal lamina.

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21
Q

What is the Sarcoplasm?

A
  • The cytoplasm of muscle fibres.
  • Densely packed with myofibrils.
  • It suspends myofibrillar proteins + organelles.
22
Q

What percentage of space does the Sarcoplasm take up of a muscle fibre?

A

9%.

23
Q

List 4 contents found in the sarcoplasm.

A
  1. Ions.
  2. Enzymes.
  3. ATP.
  4. Glycogen.
24
Q

What percentage of the intracellular space of the muscle fibre does mitochondria occupy?

A

5-6%.

25
Q

What 2 things will an increase in the size + density of mitochondria lead to?

A
  • This will support energy production which can be used for muscular contraction.
  • There will be a greater concentration of enzymes to aid reactions in Oxidative Phosphorylation.
26
Q

What are Peripheral Mitochondria?

A
  • Located closer to the periphery of the cell.
  • Support active transport.
27
Q

What are Inter-Myofibril Mitochondria?

A
  • Extend inwards towards the centre of the cell.
  • Provides energy for muscular contraction.
28
Q

What is the Sarcoplasmic Reticulum?

A
  • Stores, releases + retrives calcium ions.
  • Calcium is fundamental for contraction.
29
Q

What are Transverse tubules?

A
  • Invaginations of the sarcolemma that extends inwards towards the centre of the cell.
  • Stay close to the sarcoplasmic reticulum which is important for excitation-contraction coupling.
30
Q

What is Terminal cisternae?

A
  • A region close to the sarcoplasmic reticulum.
  • Surrounds the transverse tubules.
  • Stores calcium ions which is fundamental for excitation-contraction coupling.
31
Q

What is the T-Tubule + Sarcoplasmic Reticulum mechanism?

A
  • Allows communication between the outside of the cell membrane (SR) and deep in the muscle fibre.
  • Signals would not be transmitted without these invaginations.
32
Q

How many T-tubules does a skeletal muscle have for each Sarcomere?

A

2.

33
Q

What percentage of the intracellular space do myofibrils occupy within the muscle fibre?

A

85%.

34
Q

What is the Sarcomere?

A
  • The smallest functional unit within the skeletal muscle.
  • Made up of contractile + structural proteins.
35
Q

Why is the Sarcomere regarded as a ‘Functional unit’?

A
  • Contraction of sarcomeres leads to the contraction of muscle fibres, which leads to the contraction of the entire muscle.
36
Q

What proteins does the sarcomere consist of?

A
  • Myosin Filament (Thick)
  • Actin Filament (Thin)
37
Q

What are Z discs?

A
  • Located on the edge of the sarcomere.
  • Structural proteins.
  • Support + define the area of the sarcomere.
38
Q

What is the H zone?

A

The distance between actin filaments.

39
Q

What is the A band?

A

The length of the myosin filament.

40
Q

What is the I band?

A

The distance from the edge of myosin to the z-line.

41
Q

What is the structure of the Myosin (Thick) filament?

A
  • Made up of 2 myosin heavy chain molecules + 2 myosin light chain molecules.
  • Consists of a tail, hinge + head region.
42
Q

What are the 2 binding sites located at the head region of the ‘myosin heavy chain molecule’?

A
  • Actin binding site.
  • ATP binding site.
43
Q

What is the Actin Binding site?

A
  • Important for binding strokes + contracting the sarcomere.
44
Q

What is the ATP Binding site?

A
  • Important for energizing the binding strokes.
45
Q

What is located at the hinge region of the ‘myosin light chain molecule’?

A
  • Regularoty protein.
46
Q

What do the heads of the ‘myosin heavy chain molecules’ contain?

A
  • ATPase.
47
Q

Outline the importance of ATPase.

A
  • Will break down ATP into ADP + a free phosphate ion.
  • This releases energy to power the contraction.
48
Q

What is the structure of the actin (thin) filament?

A
  • Made up of 2 actin chains.
  • Troponin + Tropomysoin span the actin chain.
49
Q

What is the functions of ‘Troponin’ and ‘Tropomyosin’?

A
  • Both will shield actin binding sites so when at rest our sarcomeres aren’t contracting.
50
Q

What is Titan, and what is its function?

A
  • A structural protein.
  • Provides elasticity.
  • Stabilizes myosin.
  • Assists eccentric muscular contractions.
51
Q

What are satellite cells?

A
  • When load is applied these cells will donate nuclei to the muscle fibre.
  • Allows muscle fibre to grow more protein.
  • Leading to muscular hypertrophy.

Therapeutic Exercise Year 1 (69 decks)

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