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Bio 7: Run For Your Life > Muscles > Flashcards

Muscles Flashcards

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1
Q

Describe the structure of skeletal muscle - 6

A
  • Muscle
  • Bundle of muscle fibres
  • Muscle fibre
  • Myofibrils
  • Sarcomere
  • Protein filaments : actin and myosin
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2
Q

Describe a muscle fibre 4

A
  • Muscle cells fuse to form a very long multinucleated cell
  • Surrounded by a cell membrane called sarcolemma
  • Have lots of mitochrondia - provides ATP for muscle contraction
  • Contains sarcoplasm : cytoplasm of striated muscle cells
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3
Q

Why are the muscle fibre cells multinucleated? 3

A
  • Single nucleus not enough to control metabolism of long cell
  • Time taken for protein to be made in cell is too long
  • To reach furthest parts of the cell
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4
Q

What does the sacroplasm contain? 2

A
  • Folds called transverse tubules [T] help to spread electrical impluses throughout the sacroplasm
  • To reach all parts of the muscle fibres
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5
Q

What runs through the sacroplasm?

A

Sarcoplasmic reticulum

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6
Q

What is the sarcoplasmic reticulum?

A

A network of internal membranes running through the sarcoplasm

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7
Q

What does the sarcoplasmic reticulum do?

A

Stores and releases calcium ions needed for muscle contraction

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8
Q

What word is used to describe the muscle fibre patterns?

A

Striated - pattern of light and dark bands

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9
Q

What are bundles of muscle fibres?

A

Bundles bound together by connective tissue continuous with tendons

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10
Q

How long across is each bundle of muscle fibres?

A

2cm across

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11
Q

What does the connective tissue in bundle of muscle fibres contain?

A

Blood vessels

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12
Q

Where are myofibrils found?

A

Sacroplasm

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13
Q

What are myofibrils?

A

Long cylinderal organelles highly specialised for contraction

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14
Q

What are myofibrils made up of?

A

Repeated contracile units arranged end to end (sacromeres]

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15
Q

What are sacromeres made up of?

A

Protein filaments:

  • Actin
  • Myosin
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16
Q

Is actin thin/thick?

A

Thin

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17
Q

Is myosin thin/thick?

A

Thick

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18
Q

How does the sacromere contract?

A

Through the co-ordinated sliding of protein filaments past each other

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19
Q

How does the sacromere return to its original shape?

A

Through the returning of sliding protein filaments to their original length when the muscle relaxes

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20
Q

When labelling an actin and myosin diagram what should be labelled? 5

A
  • Z line
  • M line
  • A band
  • I band
  • H Zone
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21
Q

What is the z line?

A

Marks the ends of the sacromere, where sarcomeres joined together sideways

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22
Q

What is the m line?

A

The middle of each sacromere in the middle of the myosin filaments

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23
Q

What are the A bands?

A

Dark bands where the actin and myosin is overlapping

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24
Q

What are the I bands?

A

Light bands with thin actin only

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25
Q

What do the intermediately coloured bands contain?

A

Myosin only

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26
Q

What do the actin and myosin do in contraction?

A
  • Actin moves within myosin, sliding over each other
  • Sacromere shortens in length
  • Muscle length shortens
  • Actin and myosin DO NOT shorten themselves
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27
Q

What are the 2 proteins between actin filaments?

A
  • Troponin

- Tropomyosin

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28
Q

Troponin and tropomyosin are…

A

…attracted to each other

29
Q

What are the myosin filaments made up of?

A
  • Hinged globular heads that move back and forth

- With binding sites for actin and ATP

30
Q

What do actin filaments have?

A

Actin-myosin binding sites for myosin heads

31
Q

Part 1 of sliding filament theory - myosin binding to actin 10

A
  • Nerve impulsive [action potential] arrives from a motor neurone at a neuromuscular junction
  • Stimulates muscle cell
  • Depolarises sacrolema
  • Depolarisation spreads down T tubules to sacrcoplasmic reticulum
  • SR releases stored calcium ions into sacroplasm
  • Calcium ions bind to troponin
  • Causes it to change shape
  • Pulls attached tropomyosin out of actin myosin binding site
  • Exposes actin myosin binding sites on actin filaments
  • Allows myosin head to bind to actin filament forming an actin myosin cross bridge
32
Q

Part 2 of sliding filament theory - the role of ATP 10

A
  • Calcium ions activate ATPase enzyme when actin and myosin bind
  • Causes breakdown of ATP into ADP and Pi to provide energy needed for contraction
  • Myosin changes shape
  • Myosin head moves forward
  • Pulls actin filament along over it
  • ATP molecule binds to myosin head
  • Causes it to detach from the actin filament, breaking the actin myosin bridge
  • An ATPase on the myosin head hydrolyses ATP to form ADP and Pi
  • Causes change in myosin head shape, returning it to its upright position
  • Enables cycle to start again
33
Q

Explain how muscle contraction stops

A
  • Muscle stopped being stimulated by nerve impulses
  • Calcium ions leave binding sites on troponin molecules
  • Moved by active transport back into sarcoplasmic reticulum
  • Troponin molecules return to original shape
  • Pulls attached tropomyosin molecules with them
  • Block actin-myosin binding sites
  • Muscles not contracted
  • No myosin heads attached to actin filaments - no cross bridges
  • Actin filaments slide back to relaxed position
  • Lengthens sacromere
34
Q

What is skeletal muscle used for?

A

Movement

35
Q

How do the arms move? 5

A
  • Bicep stimulated
  • Bicep contracts
  • Tricep relaxes
  • Pulls on tendon
  • Bends/flexes the arm
36
Q

How do muscles work? 4

A
  • Muscles contract/relax
  • To pull on bones at joints
  • Joints bent [flexed]/straightened [extended]
  • Muscles can only pull
37
Q

What are antagonistic pairs/why do muscles work in antagonistic pairs? 3

A
  • Muscles can only work in one direction
  • Therefore there is a need to create opposite forces
  • Two muscles : extensor and flexor are needed to move bone
38
Q

What is an extensor?

A

Muscle causing the extension of a joint when it contracts

39
Q

What is a flexor?

A

Muscle causing the flexing of a joint when it contracts

40
Q

What are ligaments?

A
  • Attach bone to other bone
  • Allow some movement
  • Provides stability
41
Q

How do ligaments provide stability?

A

They have lots of elastic tissue

42
Q

What are tendons?

A
  • Attach muscles to bones
  • Enable muscles to move joints
  • Relatively inelastic
43
Q

Why are tendons relatively inelastic?

A

So all the force is transmitted to the bone

44
Q

What is a joint?

A

Point where two bones meet

45
Q

What are the synovial joints?

A

Joints allowing for bone movement

46
Q

What are synovial joints separated by?

A

A cavity filled with synovial fluid

47
Q

What is the synovial fluid?

A

A viscious and sticky lubricant allowing for free movement of bones

48
Q

What is the cartilage like?

A

White, hard and rubbery

49
Q

What does the cartilage do?

A

Protects bones within joints and is a shock absorber

50
Q

What are the two types of muscle fibres?

A
  • Slow twitch

- Fast twitch

51
Q

What affects proportion of slow twitch to high twitch muscle fibres?

A
  • Genetics
  • Endurance training
  • Type of muscles
52
Q

What proportion of muscle fibres do endurance trainers/endurance muscles [e.g back muscles] have?

A

High slow twitch to fast twitch proportion

53
Q

List the properties of slow twitch fibres compared to fast twitch 9

A
  • More aerobic respiration
  • Darker muscle fibres: higher myoglobin levels
  • High amounts of respiratory enzymes
  • More capillaries
  • Lower glycogen content
  • More mitochondria
  • Less sarcoplasmic reticulum
  • Fatigues less quickly
  • Lower levels of creatine phosphate
54
Q

List the properties of fast twitch fibres compared to slow twitch 9

A
  • More anaerobic respiration
  • Higher levels of creatine phosphate
  • Higher glycogen content
  • Less mitochondria
  • Less capillaries
  • More sarcoplasmic reticulum
  • Fatigues more quickly
  • Less respiratory enzymes
  • Ligher muscle fibres: lower myoglobin levels
  • Higher levels of creatine phosphate
55
Q

Why are slow twitch muscle fibres darker? 3

A
  • Higher myoglobin levels
  • Higher O2 store
  • Ensures sufficient supply of O2 for aerobic respiration
56
Q

Why do slow twitch muscle fibres have more capillaries? 3

A
  • Better blood supply
  • Facilitates faster supply of glucose and oxygen for aerobic respiration
  • Faster removal of CO2
57
Q

Why are slow twitch muscle fibres have more mitochondria?

A

Krebs Cycle and oxidative phosphorylation take place here for aerobic respiration

58
Q

Why do slow twitch muscle fibres have lower glycogen content? 3

A
  • Slow twitch in use fairly constantly
  • No need to store glucose
  • Just needs continual supply
59
Q

Why do slow twitch muscle fibres have less sarcoplasmic reticulum? 3

A
  • Less Ca+ needed to be released
  • Actin/myosin don’t need as quick initiation
  • Muscle contraction is slower
60
Q

Why do slow twitch muscles fatigue less quickly?

A

Less anaerobic respiration so less lactic acid

61
Q

Why are fast twitch muscle fibres lighter? 2

A
  • Lower myoglobin levels

- Anaerobic respiration occurs so no oxygen needs to be stored in these fibres

62
Q

Why do slow twitch muscle fibres have less capillaries? 3

A

Mostly anaerobic respiration so no oxygen supply needed

63
Q

Why do slow twitch muscle fibres higher glycogen content? 3

A
  • Only used occasionally
  • When used to large supply of glucose needed
  • Stored there in preparation
64
Q

Why do slow twitch muscle fibres less mitochondria? 3

A
  • Mostly undergoes anaerobic respiration
  • Involves glycolysis
  • Occurs in cytoplasm
65
Q

Why do slow twitch muscle fibres have more sarcoplasmic reticulum? 3

A
  • Releases more Ca+ ions
  • Initiates movements of actin and myosin
  • Faster muscle contraction
66
Q

Why do slow twitch muscle fibres fatigue more quickly? 3

A

Anaerobic respiration releases lactic acid

67
Q

What is the purpose of slow twitch fibres? 2

A
  • Specialised for slower, sustained contraction

- Long periods of exercise and endurance activities: marathons/posture

68
Q

What is the purpose of fast twitch fibres? 2

A
  • Specialised for rapid, intense contraction

- Short bursts of speed and power: eye movement and sprinting

69
Q

What is myoglobin? 4

A
  • Similar to haemoglobin
  • Has a high affinity for oxygen
  • Only releases it when O2 concentration falls very low
  • Therefore acts as oxygen store

Bio 7: Run For Your Life (11 decks)

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