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Muscle contraction Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the relationship between the CNS and Muscular movement?

A

The CNS (brain and spinal cord) receives sensory information and decides what kind of response is needed.

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2
Q

If the response needed is movement, the CNS…

A

sends signals along neurons to tell Skeletal muscle to contract.

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3
Q

What is Skeletal muscle?

A

Skeletal muscle (also called striated, striped or voluntary muscle) is the type of muscle you use to move, e.g the biceps and triceps move the lower arm.

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4
Q

What makes up Skeletal muscle?

A

Skeletal muscle is made up of large bundles of long cells called muscle fibres.

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5
Q

What is the name of the cell membrane of muscle fibre cells?

A

Sacrcolemma

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6
Q

Bits of the sarcolemma fold inwards across

A

the muscle fibre and stick into the sarcoplasm (a muscle cell’s cytoplasm)

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7
Q

When the sarcolemma folds this is called…

A

transverse tubules (T) tubules.

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8
Q

What are transverse (T) tubules useful for?

A

Transverse (T) tubules help to help spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibres.

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9
Q

A network of internal membranes called the …

A

sarcoplasmic reticulum runs through the sarcoplasm.

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10
Q

What does the sarcoplasmic reticulum in relation to muscle contraction?

A

The sarcoplasmic reticulum stores and release calcium ions that are needed for muscle contraction.

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11
Q

Why do muscle fibres have a lot of mitochondria?

A

Muscle fibres have a lot of mitochondria to provide the ATP that’s needed for muscle contraction.

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12
Q

muscles cells contain many cells, this is called?

A

They are multinucleate.

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13
Q

Muscle fibres have lots of long, cylindrical organelles called …

A

myofibrils.

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14
Q

What makes up myofibrils?

A

They’re made up of proteins and are highly specialised for contraction.

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15
Q

Myofibrils contain bundles of:

A

thick and thin myofilaments that move past each other to make the muscle contract.

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16
Q

Thick myofilaments are made of the protein …

A

myosin

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17
Q

Thin myofilaments are made of the protein …

A

actin.

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18
Q

If you look at a myofibril under a microscope you’ll see a pattern of:

A

alternating dark and white bands.

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19
Q

Dark bands contain the …

A

thick myosin filaments and some overlapping thin actin filaments - these are called A-bands.

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20
Q

Light bands contain…

A

thin actin filaments only these are called L bands.

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21
Q

A myofibril is made up :

A

short units called sarcomeres.

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22
Q

The ends of each sarcomere are marked with a…

A

Z line.

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23
Q

In the middle of each sarcomere is an …

A

M line.

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24
Q

What is the m line?

A

The M-line is the middle of the myosin filaments.

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25
Q

Around the M-line is the …

A

H-Zone.

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26
Q

The H-zone only contains…

A

myosin filaments.

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27
Q

Myosin and actin filaments slide over another to make :

A

the sarcomeres contract, the myofilaments themselves don’t contract.

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28
Q

The simultaneous contraction of lots of sarcomeres…

A

means the myofibrils and muscle fibres contract.

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29
Q

Sarcomeres return to their…

A

Original length as the muscle relaxes.

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30
Q

What structure do myosin filaments have that are hinged?

A

Myosin filaments have globular heads that are hinged, so they can move back and forth.

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31
Q

Does myosin have a binding site? Explain.

A

Each myosin head has a binding site for actin and a binding site for ATP.

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32
Q

Do Actin filaments have binding sites?

A

Actin filaments have binding sites for myosin heads, called actin myosin-binding sites

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33
Q

What two other proteins are found between actin filaments?

A

Two other proteins called tropomyosin and troponin are found between actin filaments.

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34
Q

What is the purpose of troponin and tropomyosin being attached together?

A

These proteins are attached to each other and they help myofilaments move past each other.

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35
Q

In a resting (unstimulated) muscle the actin myosin-binding site is blocked by …

A

tropomyosin, which is held by troponin.

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36
Q

What is the reason for tropomyosin blocking the actin-myosin binding site?

A

So myofilaments can’t slide past each other because the myosin heads can’t bind to the actin myosin-binding site on the actin filaments.

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37
Q

What happens when the action potential from a motor neurone stimulates a muscle cell?

A

When an action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma

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38
Q

What happens to depolarisation after the sarcolemma?

A

Depolarisation spreads down the T-tubules to the sarcolemma reticulum.

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39
Q

What does the action potential cause the sarcoplasmic reticulum to release?

A

Calcium ions into the sarcoplasm.

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40
Q

Calcium ions bind to troponin, causing it to …

A

change shape.

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41
Q

What happens after when the troponin binds to the calcium ions.

A

Calcium ions bind to troponin, causing it to change shape. This pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament.

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42
Q

What happens after, when tropomyosin is pulled out of the actin-myosin active site?

A

This exposes the binding site, which allows the myosin head to bind.

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43
Q

The bond formed when a myosin head binds to an actin filament is called an:

A

actin-myosin cross bridge.

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44
Q

Calcium ions also activate the enzyme…

A

ATPase

45
Q

ATPase breaks down …

A

ATP (into ADP + P) to provide the energy needed for muscle contraction.

46
Q

The energy released from ATP moves the…

A

myosin head which pulls the actin filament along in a kind of rowing action.

47
Q

ATP also provides the energy to break the actin-myosin cross-bridge, so the…

A

myosin head detaches from the actin filament after it’s moved.

48
Q

The myosin head reattaches to a …

A

the different binding site further along the actin filament. A new actin-myosin cross-bridge is formed and the cycle is repeated.

49
Q

How do cross-bridges cause muscle contraction?

A

Many cross-bridges form and break very rapidly, pulling the actin filaments along-which shortens the sarcomere, causing the muscle to contract.

50
Q

What happens to the calcium ions when the muscles stop being stimulated?

A

When the muscles stop being stimulated, calcium ions leave their binding sites on the troponin molecules and are moved by active transport back into the sarcoplasmic reticulum.

51
Q

What happens to the troponin molecule when the calcium ions leave the active site?

A

The troponin molecules return to their original shape, pulling the attached tropomyosin molecules with them. This means tropomyosin molecules block the actin-myosin binding site again.

52
Q

Muscles aren’t contracted because…

A

no myosin heads are attached to actin filaments.

53
Q

What happens to the actin filaments when the muscle does not contract?

A

The actin filaments slide back to their relaxed position, which lengthens the sarcomere.

54
Q

(Aerobic respiration) Most ATP is generated via…

A

Oxidative phosphorylation in the cell’s mitochondria

55
Q

(Aerobic respiration) aerobic respiration only works when there’s oxygen so it’s good for…

A

long periods of low-intensity exercise.

56
Q

(Anaerobic respiration) ATP is made rapidly with …

A

glycolysis

57
Q

(Anaerobic respiration) The end product of glycolysis is…

A

pyruvate, which is converted into lactate by lactate fermentation.

58
Q

(Anaerobic respiration) Lactate can quickly build up in the muscles and cause…

A

muscle fatigue.

59
Q

(Anaerobic respiration) Anaerobic respiration is good for…

A

short periods of hard exercise.

60
Q

(ATP-Creatine Phosphate (CP) System) ATP is made by …

A

Phosphorylating ADP adding a phosphate group taken from creatine phosphate.

61
Q

(ATP-Creatine Phosphate (CP) System) CP is STORED … and the ATP-CP system generates ATP very quickly.

A

inside cells

62
Q

CP runs out after a few seconds so it’s used during …

A

short bursts of vigorous exercise.

63
Q

The ATP-CP system is anaerobic and it’s …

A

alactic (it doesn’t form any lactate)

64
Q

What is a neuromuscular junction?

A

A neuromuscular junction is a synapse between a motor neurone and a muscle cell.

65
Q

Neuromuscular junctions use the neurotransmitter acetylcholine (ACh), which binds to receptors called…

A

nicotinic cholinergic receptors.

66
Q

Neuromuscular junctions work in the same way as …

A

synapses between neurones they release a neurotransmitter, which triggers depolarization in the postsynaptic cell.

67
Q

Depolarisation of a muscle cell always…

A

causes it to contract (if the threshold level is reached)

68
Q

Acetylcholinesterase (AChE) stored in clefts on…

A

the postsynaptic membrane is released to break down acetylcholine after use.

69
Q

Sometimes a chemical (e.g. a drug) may block the release of the neurotransmitter or affect the way it…

A

binds on the receptor on the postsynaptic membrane.

70
Q

When a chemical binds to the receptor, it may prevent the action potential from being passed on to…

A

the muscle, so the muscle won’t contract.

71
Q

Inhibiting muscle contraction could prove fatal if it affects the muscles involved in…

A

breathing, e.g. the diaphragm and intercostal muscles. If they can’t contract, ventilation can’t take place and the organism can’t respire aerobically.

72
Q

Skeletal muscle contraction is controlled…

A

consciously.

73
Q

Skeletal muscle is made up of many fibres that have…

A

many nuclei.

74
Q

You can see regular … (a striped pattern) under the microscope.

A

cross-striations

75
Q

Some muscle fibres contract very quickly - they’re used for…

A

speed and strength but fatigue quickly.

76
Q

Some muscle fibres contract slowly and fatigue slowly - they’re used for…

A

endurance and posture.

77
Q

What would you see under a microscope of a skeletal muscle?

A

> Cross striation - alternating dark and light pink stripes these are the A bands and L bands

> Many nuclei in each muscle fibre.

78
Q

Involuntary muscle contraction is controlled…

A

unconsciously.

79
Q

Involuntary muscle contraction is called smooth muscle because…

A

it doesn’t have the striped appearance of voluntary muscle.

80
Q

smooth muscle is found in the walls of your…

A

hollow internal organs, e.g the gut, the blood vessels.

81
Q

your gut smooth muscles contract to move food along, this is called…

A

peristalsis.

82
Q

Your blood vessel smooth muscles contract to …

A

reduce the flow of blood.

83
Q

Each muscle fibre has one…

A

nucleus.

84
Q

The muscle fibres are …, and they’re only 0.2mm long.

A

spindled shaped with pointed ends.

85
Q

The muscles contract…

A

slowly and don’t fatigue.

86
Q

Cardiac muscles contract on its own - it’s…

A

myogenic

87
Q

The rate of contraction in the cardiac muscles is controlled involuntarily by the…

A

autonomic nervous system.

88
Q

Cardiac muscles are found in the …

A

walls of your heart.

89
Q

Cardiac muscles are made of muscle fibres connected by…

A

intercalated discs, which have low electrical resistance so nerve impulses pass easily between cells

90
Q

The muscle fibres are branched to allow…

A

nerve impulses to spread quickly through the whole muscle.

91
Q

Each muscle fibre in the cardiac muscle only has…

A

one nucleus.

92
Q

The muscle fibre in the cardiac muscles is shaped like…

A

cylinders and they’re about 0.1mm long.

93
Q

You can see some cross-striations but the striped pattern isn’t as strong as it is in the…

A

voluntary muscle.

94
Q

Cardiac muscles contract…

A

rhythmically and don’t fatigue.

95
Q

If you have access to specialist equipment you may be able to investigate muscle contraction and fatigue by monitoring the … that occurs.

A

electrical activity.

96
Q

Muscles contract in response to nerve impulses these are …

A

electrical signals.

97
Q

Electrical signals in muscles can be detected by …. places on the skin

A

electrodes.

98
Q

Electrodes connected to a computer produces electrical signals, this procedure is called…

A

electromyography.

99
Q

Electromyography generates electrical signal readings which is called

A

electromyogram.

100
Q

First of all, you need to attach … to places that you want to record from.

A

two electrodes.

101
Q

A third electrode goes on an … (such as the bony wrist area to act as a control.)

A

inactive point

102
Q

Switch off any other electrical equipment as this generates …

A

a noise that interferes with electrical signals from the muscle.

103
Q

Connect the electrodes to an …

A

amplifier and a computer.

104
Q

Keep the muscles… you should see a straight line on the electromyograph.

A

relaxed.

105
Q

Then contract the muscle by bending your arm. You should see spikes on the graph as … are activated to contract muscles.

A

motor units.

106
Q

If you then lift a weight, the amplitude of the trace on the graph will increase there are more…

A

electrical signals because more motor units are required to lift the weight.

107
Q

If you continue to lift the weight your muscles will begin to …

A

fatigue.

108
Q

During fatigue, the electromyograph amplitude will increase. This is because your brain is trying to activate …

A

more motor units to generate the force needed to hold the weight up.

Biology (18 decks)

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