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A-Level Biology ONLY > I/E: Muscle Contraction > Flashcards

I/E: Muscle Contraction Flashcards

(54 cards)

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1
Q

Skeletal muscles

A

Used for movement and attached to bones by tendons.

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2
Q

Ligaments

A

Attach bones to other bones.

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3
Q

What type of muscles are skeletal muscles?

A

Antagonistic - contract and relax to move bones at a joint.

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4
Q

Explain the concept of antagonistic pairs:

A

One muscle contracts and the other relaxes.

Contracting muscle = agonist

Relaxing muscle = antagonist

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5
Q

What are skeletal muscles made up of?

A

Muscle fibres

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6
Q

Sarcolemma

A

Cell membrane of muscle fibres

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7
Q

Transverse (T) tubules

A

Inner folds of the sarcolemma that help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.

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8
Q

Sarcoplasm

A

Cytoplasm of the muscle cell.

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9
Q

Muscle fibres

A

Large bundles of long cells that make up the skeletal muscle.

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10
Q

Sarcoplasmic reticulum

A

A network of internal membranes that run through the sarcoplasm, storing and releasing calcium ions that are needed for muscle contraction.

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11
Q

Myofibrils

A

Long, cylindrical organelles found in skeletal muscles that are made up of proteins and are highly specialised for contraction.

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12
Q

Give 3 characteristics of muscle cells:

A
  • Lots of mitochondria to provide ATP for muscle contraction.
  • Multinucleate - contain many nuclei.
  • Myofibrils - highly specialised for contraction.
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13
Q

Describe the overall structure of a skeletal muscle:

A

Muscle –> muscle fibre –> myofibril

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14
Q

What are myofibrils made up of?

A

Myosin and actin (myofilaments) that move past each other to make muscles contract.

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15
Q

Used for movement and attached to bones by tendons.

A

Skeletal muscles

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16
Q

Attach bones to other bones.

A

Ligaments

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17
Q

Cell membrane of muscle fibres

A

Sarcolemma

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18
Q

Inner folds of the sarcolemma that help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.

A

Transverse (T) tubules

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19
Q

Cytoplasm of the muscle cell.

A

Sarcoplasm

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20
Q

Large bundles of long cells that make up the skeletal muscle.

A

Muscle fibres

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21
Q

A network of internal membranes that run through the sarcoplasm, storing and releasing calcium ions that are needed for muscle contraction.

A

Sarcoplasmic reticulum

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22
Q

Long, cylindrical organelles found in skeletal muscles that are made up of proteins and are highly specialised for contraction.

23
Q

Myosin

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A

Protein that makes up thick myofilaments.

24
Q

Actin

Study These Flashcards
A

Protein that makes up thin myofilaments.

25
A-bands
Dark bands of the myofibril that contains the thick myosin filaments and some overlapping thin actin filaments.
26
I-bands
Light bands of the myofibril that contains thin actin filaments only.
27
Sarcomeres
Short units that makes up the myofibril.
28
Z-line
Marks the end of each sarcomere.
29
M-line
Marks the middle of each sarcomere.
30
H-zone
The zone around the M-line that only contains myosin filaments.
31
Protein that makes up thick myofilaments.
Myosin
32
Protein that makes up thin myofilaments.
Actin
33
Dark bands of the myofibril that contains the thick myosin filaments and some overlapping thin actin filaments.
A-bands
34
Light bands of the myofibril that contains thin actin filaments only.
I-bands
35
Short units that makes up the myofibril.
Sarcomeres
36
Marks the end of each sarcomere.
Z-line
37
Marks the middle of each sarcomere.
M-line
38
The zone around the M-line that only contains myosin filaments.
H-zone
39
Explain the sliding filament theory in relation to muscle contraction:
* Myosin and actin filaments slide over one another to make the sarcomeres contract. * Simultaneous contraction of lots of sarcomeres means myofibrils and muscles contract. * Sarcomeres return to their original length as the muscle relaxes.
40
According to the sliding filament theory, during muscle contraction what happens to the length of: * the A-band? * the I-band? * the H-zone? * the sarcomere as a whole?
A-band stays the same length I-band gets shorter H-zone gets shorter Sarcomeres get shorter.
41
Describe the heads of myosin filaments:
* Globular * Hinged * Binding site for actin * Binding site for ATP.
42
Actin-myosin binding sites
Binding sites for myosin heads found on actin filaments.
43
Binding sites for myosin heads found on actin filaments.
Actin-myosin binding sitesActin
44
Tropomyosin
Protein found between actin filaments that helps myofilaments move past each other.
45
Protein found between actin filaments that helps myofilaments move past each other.
Tropomyosin
46
# 11 points/steps Describe how muscle contraction is triggered by an influc of calcium ions:
1. Stimulation of muscle cell depolarises the sarcolemma and spreads down the T-tubules to the sarcoplasmic reticulum. 2. SR releases stored Ca2+ ions into the sarcoplasm. 3. Ca2+ binds to protein attached to tropomyosin, causing it to change shape - **pulls attached tropomyosin out of the actin-myosin binding site.** 4. Exposes the binding site, allowing the myosin head to bind. 5. Actin-myosin cross bridge forms. 6. Ca2+ activates ATP hydrolase which hydrolyses ATP to provide energy. 7. Causes myosin head to bend, pullling the actin filament in a rowing action. 8. Another ATP molecule provides energy to break actin-myosin cross bridge, so myosin head detached from actin filament. 9. Myosin head reattaches to a different binding site further along the actin filament. 10. New actin-myosin cross bridge forms and the cycle repeats as long as Ca ions are present. 11. This shortens the sarcomere.
47
In resting muscles, what blocks the binding sites? ## Footnote *What does this mean?*
Actin-myosin binding site is blocked by tropomyosin. ## Footnote *Myofilaments can't slide past each other because the myosin heads can't bind to the actin-myosin binding site on the actin filaments.*
48
In a muscle, what happens when excitation stops/the muscle stops being stimulated?
1. Ca2+ leave binding sites and are moved by active transport back into sarcoplasmic reticulum. 2. ATP is needed. 3. Causes the tropomyosin to move back, so they block the actin-myosin binding sites again. 4. Muscles aren't contracted as there are no myosin heads attached to actin filaments. 5. Actin filaments slide back to relaxed position, lengthening the sarcomere.
49
Name the main 3 ways that ATP is continually generated so that exercise can continue:
1. Aerobic respiration 2. Anaerobic respiration 3. ATP-Phosphocreatine (PCr) system
50
How is most ATP generated during aerobic respiration? ## Footnote *What exercise is aerobic respiration good for an why?*
* Most ATP generated via oxidative phosphorylation in mitochondria. * *Good for low-intensity exercise as it only works when there's oxygen.*
51
How is ATP generated during anaerobic respiration? ## Footnote *What type of exercise is anaerobic respiration good for and why?*
* ATP is rapidly made by glycolysis. * *Good for short periods of hard exercise, as the end product of glycolysis is pyruvate which is converted to lactate by lactate fermentation.* * *Lactate build up can cause muscle fatigue.*
52
How does the PCr system generate ATP? Where is PCr stored? *What exercise is PCr best for and why?*
* ATP is phosphorylated using a phosphate group taken from PCr. * Stored inside cells. * Best for short bursts of vigorous exercise as it generates ATP very quickly and runs out after a few seconds.
53
What are the two types of muscle fibres in skeletal muscles?
Slow twitch and fast twitch
54
What are the differences between slow and fast twitch muscle fibres? * Contraction speed? * Found in high proportion where? * Good for what type of exercise? * Tiredness? * Releasing energy? * Colour? * Mitochondria and blood vessels?
* ST contract slowly, FT contract quickly. * ST high proportion in muscles used for posture, FT high proportion in muscles used for fast movement. * ST good for endurance activities, FT good for short burst of speed and power. * ST can work for a long time without getting tired, FT get tired easily. * ST release energy slowly through aerobic respiration, FT release energy quickly through anaerobic respiration using glycogen. * ST reddish colour as rich in myoglobin, FT whitish in colour as low in myoglobin. * ST have lots of mitochondria and blood vessels supplying muscle with oxygen, FT have few mitochondria and blood vessels.

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