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A-Level Biology > Muscles > Flashcards

Muscles Flashcards

1
Q

What is the cytoplasm called in muscle fibres?

A

Sarcoplasm

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2
Q

What is it called that muscle fibres have many nuclei?

A

Multinucleated

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3
Q

What is the cell membrane called in muscle fibres?

A

Sarcolemma

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4
Q

What surrounds myofibrils?

A

Sarcoplasm

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5
Q

Why do you nuclei need to be dotted all over sarcoplasm?

A

Transcription

All muscle cells controlled

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6
Q

What organelle will be in large number in sarcoplasm?

A

Mitochondria
RER
SER

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7
Q

Why is there lots of mitochondria in sarcoplasm?

A

ATP for contraction + protein synthesis

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8
Q

Why is there lots of RER in the sarcoplasm?

A

Protein synthesis

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9
Q

Why is there lots of SER in the sarcoplasm?

A

Storage of Ca2+ for contraction

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10
Q

Describe the structure of striated muscles

A

Individual filaments called myofibrils
Fuse together to form muscle fibres
When individual cells fuse together + microfibrils lay parallel
Each fibre shares sarcoplasm surrounding myofibrils
And sarcolemma
A single muscle cell = multinucleated

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11
Q

What do myofibrils consist of?

A

Actin

Myosin

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12
Q

Describe actin

A

Thinner

Made up of 2 strands coiled around each other

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13
Q

Describe myosin

A

Thicker
Consists of rod-shaped fibres with “bulbed heads”
Bulbed heads project outwards

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14
Q

What do myofibrils also contain?

A

Multiple sarcomeres

Banding pattern

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15
Q

What does the banding pattern of myofibrils cause?

A

Them to appear striped

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16
Q

What are the two main components of the sarcomere?

A

Dark bands

Light bands

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17
Q

What type of bands are dark bands?

A

Anisotropic bands

A - bands

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18
Q

What are the dark bands?

A

Actin + myosin overlap

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19
Q

What do the dark bands depend on?

A

Myosin length

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20
Q

What are the light bands?

A

No overlap

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21
Q

What type of bands are the light bands?

A

Isotropic bands

I - bands

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22
Q

What is the area called where there is only myosin filaments?

A

H - zone

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23
Q

What is the structure of an I - band?

A

Thin actin filaments only

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24
Q

What is the structure of the H - zone?

A

Thick myosin filaments only

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25
Q

What is the structure of an A - band?

A

Thick + thin filaments

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26
Q

How would you calculate the mean length of one sarcomere?

A

Measure the length from one z - line to another

Repeat + calculate

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27
Q

When a muscle contract what happens to the sarcomere?

A

It shortens

Patterns of light + dark bands change

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28
Q

Why do the patterns of the bands change when a muscle contracts?

A

Actin + myosin slide over each other

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29
Q

Why do the sarcomere shorten when the muscle contracts?

A

Sarcomere slides inwards = shortens

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30
Q

What are the 3 connective tissues?

A

Tendon
Ligament
Cartilage

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31
Q

What does the tendon connect?

A

Bone to muscle

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32
Q

What does the ligament connect?

A

Bone to bone

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33
Q

What does the cartilage connect?

A

Found between bones - “shock absorber”

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34
Q

What are muscles?

A

Bundle of fibres
Different structures
Different jobs

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35
Q

What are the three types of muscle?

A

Cardiac
Skeletal
Smooth

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36
Q

What is a cardiac muscle?

A

Present in the heart + acts involuntary (myogenic)

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37
Q

What is a skeletal muscle?

A

Attached to bones, vast majority of muscle, discontinuous contraction + controlled voluntarily

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38
Q

What is a smooth muscle?

A

Involuntary muscle, found in the gut, blood vessel walls + iris
Slow weak contraction

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39
Q

How do muscles act by?

A

Receiving nerve impulse
Work antagonistic pairs (do opposite jobs)
Pulling bones

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40
Q

What is antagonistic?

A

One muscle (prime mover) contracts + the other (antagonist) relaxes

41
Q

What are myofibrils individually?

42
Q

What are the two types of fibres?

A

Slow twitch

Fat twitch

43
Q

What is the speed of contraction for a fast twitch fibre?

44
Q

What is the speed of contraction for a slow twitch fibre?

45
Q

What is the power of contraction for a fast twitch fibre?

A

High intensity

46
Q

What is the power of contraction for a slow twitch fibre?

A

Low intensity

BUT can contract for a prolonged amount of time

47
Q

What is the type of activity of a fast twitch fibre?

A

High level of activity

eg. sprinting

48
Q

What is the type of activity of a slow twitch fibre?

A

Low level of activity (endurance)

eg. walking + long distance run

49
Q

What type of respiration for a fast twitch fibre?

50
Q

What type of respiration for a slow twitch fibre?

51
Q

What is an example of a muscle containing fast twitch fibres?

52
Q

What is an example of a muscle containing slow twitch fibres?

A

Calf muscles

53
Q

What are the adaptions of a slow twitch muscle fibre?

A 
Large amount of myoglobin 
Good supply of glycogen
Good blood vessel network
Many mitochondria 
Small diameter
Darker in colour
54
Q

Why does a slow twitch muscle have a large amount if myoglobin?

A

Steady supply of O2 for respiration (aerobic)

55
Q

Why does a slow twitch muscle have a good supply of glycogen?

A

Glucose store

56
Q

Why does a slow twitch muscle have a good blood vessel network?

A

High O2 conc

57
Q

Why does a slow twitch muscle have many mitochondria?

A

More respiration

58
Q

Why does a slow twitch muscle have a small diameter?

A

Smaller diffusion pathway

59
Q

Why does a slow twitch muscle tend to be darker in colour?

A

Good blood supply for O2

60
Q

What are the adaptations of a fast twitch muscle fibre?

A

Thicker + more myosin filaments
High conc of enzymes
Store phosphocreatine

61
Q

Why does a fast twitch muscle have a high conc of enzymes?

A

For anaerobic respiration

62
Q

Why does a fast twitch muscle have a store of phosphocreatine?

A

Provide energy to restore ATP

63
Q

Why do fast twitch muscle fibres tire quickly?

A

Fewer blood vessels
Run out of O2 much quicker
Thicker larger diffusion distance

64
Q

What colour are fast twitch muscle fibres?

65
Q

What colour are slow twitch muscle fibres?

66
Q

Why do you need two different types of muscle fibres?

A

So we can carry out two different levels of activity

67
Q

Why are fast twitch muscle fibres light?

A

Fewer blood vessels
As only needs a short burst of energy
So respires anaerobically
So doesn’t need steady supply of O2

68
Q

Why are slow twitch muscles dark?

A

Good blood vessel supply
As respires aerobically
So needs readily available O2 supply

69
Q

What is a neuromuscular junction?

A

Where a motor neuron meets skeletal muscle fibre

70
Q

What do multiple junctions allow in neuromuscular junctions?

A

Multiple fibres stimulated
Speeds up response
Contraction quicker + more powerful
Threshold met

71
Q

The strength by which a nerve or muscle fibre responds to a stimulus is independent of what?

A

Strength of the stimulus

72
Q

What happens if the stimulus does not have enough energy?

A

Threshold value not met

73
Q

What happens at a neuromuscular junction?

A

Cholinergic synapse

74
Q

What is the neurotransmitter at neuromuscular junction?

A

Acetylcholine

75
Q

What is the enzyme that hydrolyses neurotransmitters?

A

Acetylcholinesterase

76
Q

Explain how synaptic transmission takes place at neuromuscular junction

A 
Depolarisation of presynaptic neurone 
Ca channels open
Influx of Ca2+ into presynaptic knob
Vesicle fuse with membrane
Neurotransmitter diffuse across synaptic cleft
Bind to Na channels
Na channels open
Influx of NA+ into muscle fibre
New A.P if threshold exceeded
77
Q

How do muscles contract?

A

A.P travels deep into muscle fibre through:
T tubules
Branch through sarcoplasm
Cause Ca2+ released

78
Q

What type of neurone is a neuromuscular junction?

A

Motor neurone

79
Q

What is the neuromuscular junction?

A

Only excitatory

80
Q

Where does the neuromuscular junction happen?

A

Neurone to muscles

81
Q

What does the neurotransmitter bind to in a neuromuscular junction?

A

Acetylcholine binds to receptor on membrane of muscle fibre

82
Q

What is the cholinergic synapse?

A

Excitatory or inhibitory

83
Q

Where does cholinergic synapse happen?

A

Neurone to neurone or effectors

84
Q

What neurones are involved in cholinergic synapse?

85
Q

What does the neurotransmitter bind to in cholinergic synapse?

A

Acetylcholine binds to receptors on post synaptic membrane

86
Q

What is tropomyosin?

A

Long + thin fibrous strands

Wrap around actin filament

87
Q

What is troponin?

A

Globular protein involved in muscle contraction

88
Q

What doe Ca do in the sliding filament model?

A

Activates ATPase

Causes tropomyosin to change shape + free binding site

89
Q

What does ATP do in the sliding filament model?

A

Hydrolysis of ATP = energy for head to detach

90
Q

Describe the sliding filament model

A

Ca2+ channels open in plasm membrane + SR
Ca2+ released from SR + binds to troponin
Causes tropomyosin change shape + free binding site
ADP attaches to myosin head
Binds to actin binding site + flexes
ATP attaches to head = detaches
Hydrolysis of AT = energy for myosin to “cock” head + return to normal
Myosin with ADP attaches then reattaches further along actin

91
Q

What happens when the nervous stimulation stops what will happen?

A 
Ca2+ actively transported back into SR
Troponin reverts to original shape
Tropomyosin blocks binding site
Myosin head cannot bind
Muscle relaxes
92
Q

What does muscle contraction rely on energy to do?

A

Move myosin head

Reabsorb Ca+ into ER

93
Q

Where does the energy come from?

A

Oxidative phosphorylation in mitochondria

Anaerobically = phosphorylation using phosphocreatine

94
Q

What is phosphocreatine?

A

Buffer supply of phosphate stored in the muscle, used to restore ATP

95
Q

How is this energy released from phosphocreatine?

A 
Reverse supply of phosphate 
Broken down when energy is needed 
Combines with ADP to reform ATP
Immediately available
Replenished using phosphate from ATP when muscle relaxed
96
Q

What happens to the A-band in the sarcomere when a muscle contracts?

A

Stays the same

97
Q

What happens to the I-band in the sarcomere when a muscle contracts?

A

Gets shorter

98
Q

What happens to the H-zone in the sarcomere when a muscle contracts?

A

Gets shorter

A-Level Biology (21 decks)

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