Biology > Muscles > Flashcards

Muscles Flashcards

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1
Q

What are the 3 different types of muscle in the body and what are their functions?

A

Smooth muscle - contracts without conscious control
Cardiac muscle - contracts without conscious control and only in heart
Skeletal muscle - muscle you use to move

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2
Q

How are skeletal muscles attached to bones?

A

By tendons

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3
Q

How are bones attached to each other?

A

By ligaments

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4
Q

How are bones moved at a joint?

A

Pairs of skeletal muscles contract and relax

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5
Q

What are the properties of the skeleton and why is this useful?

A

The bones are incompressible so they act as levers - gives the muscle something to pull against

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6
Q

What are muscles that work together called?

A

Antagonistic pairs

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7
Q

What is the contracting muscle known as?

A

Agonist

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8
Q

What is the relaxing muscle known as?

A

Antagonist

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9
Q

Why do muscles work in pairs?

A

They can’t push - they can only pull when they contract

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10
Q

Give an example of an antagonistic pair of muscles?

A

Biceps and triceps
- When your biceps contract, your triceps relax and this pulls the bone so your arm bends at the elbow
- When your triceps contract, your biceps relax and this pulls the bone so your arm straightens at the elbow

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11
Q

What is skeletal muscle made up of?

A

Muscle fibres - formed from multiple cells fusing together

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12
Q

What is the cell membrane of muscle fibre cells called?

A

Sarcolemma

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13
Q

What is the muscle cell’s cytoplasm known as?

A

Sarcoplasm

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14
Q

What does the sarcolemma do in some part of the muscle fibres?

A

Fold inwards across the muscle fibre and stick into the sarcoplasm - known as transverse (T) tubes

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15
Q

How do T tubes aid the muscle fibre?

A

Help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre

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16
Q

What runs throughout the sarcoplasm?

A

Sarcoplasmic reticulum

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17
Q

What is the function of the sarcoplasmic reticulum?

A

Stores and releases calcium ions that are needed for muscle contraction

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18
Q

What do muscle fibres have a lot of to provide ATP?

A

Mitochondria - ATP for muscle contraction

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19
Q

What is the number of nuclei in muscle fibres like?

A

There are many of them - they are multinucleate

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20
Q

What do muscle fibres have a lot of that are specific to muscles?

A

Long, cylindrical organelles known as myofibrils that are highly specialised for contraction

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21
Q

How will a muscle fibre appear under an optical microscope?

A

Depends on how its stained and whether it’s a longitudinal (across the length) or transverse (through the structure) cross section

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22
Q

What do myofibrils contain?

A

Bundles of thick and thin myofilaments

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23
Q

What do myofilaments do to make a muscle contract?

A

Move past each other

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24
Q

What are thick myofilaments made up of?

A

The protein myosin

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25
What are thin myofilaments made up of?
The protein actin
26
What will you see if you look at a myofibril under an electron microscope?
A pattern of alternating dark and light bands
27
What do the dark bands of a myofibril contain and what are they known as?
The thick myosin filaments and some overlapping thin actin filaments - called Anisotropic (A) bands
28
What do the light bands of a myofibril contain and what are they known as?
Thin actin filaments only - called Isotropic (I) -bands
29
What is a myofibril made up of?
Many short units called sarcomeres
30
What are the ends of each sarcomere marked with?
A z-line
31
What is in the middle of each sarcomere?
The M-line - this is the middle of the myosin filaments
32
What is around the M-line in a sarcomere?
The H-zone - only contains myosin filaments
33
What is the sliding filament theory for?
Explains muscle contraction
34
What is the sliding filament theory?
This is where myosin and actin filaments slide over one another to make the sarcomeres contract
35
Do myofilaments themselves contract?
No
36
What does the simultaneous contraction of lots of sarcomeres cause?
The myofibrils and the muscle fibres contract
37
What happens to the sarcomere as the muscle relaxes?
Returns to their original length
38
During muscle contraction, what happens to the all the zones in the myofibril?
A-band stays the same length H- zone and I-band get shorter Z lines get closer together
39
What do myosin filaments have attached to them and why is their purpose?
- Globular heads that are hinged, so they can move back and forth - Binding site for actin - Binding site for ATP
40
What do actin filaments have on them and what is their purpose?
- Binding sites for myosin heads, called actin-myosin binding sites
41
What protein is found between actin filaments?
Tropomyosin - helps myofilaments move past each other
42
What are the 4 stages of muscle contraction?
1. Arrival of an action potential 2. Movement of the actin filament 3. Breaking of the cross bridge 4. Return to resting state
43
What happens when an action potential from a motor neurone stimulates a muscle cell?
It depolarises the sarcolemma
44
What happens when the sarcolemma is depolarised?
- Depolarisation spreads down the T-tubules to the sarcoplasmic reticulum - Causes it to release stored calcium ions into the sarcoplasm
45
What does the influx of calcium ions into the sarcoplasm trigger?
Muscle contraction
46
How do calcium ions interact with tropomyosin?
Bind to a protein attached to it, causing the protein to change shape - this pulls the attached tropomyosin out of the actin-myosin binding site
47
What happens when tropomyosin is removed from the binding site?
The site is exposed, so myosin head can bind
48
What is the bond between a myosin head and an actin filament called?
Actin-myosin cross bridge
49
What do calcium ions activate in muscles?
Enzyme ATP hydrolase - hydrolyses ATP to provide energy for muscle contraction
50
What does the energy released from ATP cause the myosin head to do when it is bound to the actin filament?
Hydrolysis of of ATP causes it to bend, pulling the actin filament along
51
How does the myosin head detach from the actin filament after it has pulled it along?
- Unbind ADP and Pi - Rebind a new ATP - Causes myosin to detach from the actin filament
52
How does the myosin move back to its starting position?
ATP hydrolyses, causing myosin to 're-cock' into the 'ready' position
53
What does the myosin head do once it has detached from the actin filament?
Returns to its starting position and reattaches to a different binding site further along the filament - cycle repeats
54
How does the creation of actin myosin cross bridges cause the muscle to contract?
Many of these bridges form and break rapidly, pulling the actin filament along - shortens the sarcomere causing the muscle to contract
55
What happens when a muscle stops being stimulated?
Calcium ions leave their binding sites and are moved by active transport back to sarcoplasmic reticulum
56
What happens when calcium ions leave their binding sites between actin filaments?
- Tropomyosin molecules move back and block the actin-myosin binding sites - Actin filaments slide back to their relaxed position, which lengthens the sarcomere
57
How is ATP generated for muscle contraction?
1. Aerobic respiration 2. Anaerobic respiration (lactate builds up here) 3. ATP - phosphocreatine system (PCr)
58
How is ATP made from PCr?
By phosphorylating ADP using a phosphate group from PCr ADP + PCr = ATP + Cr (creatine)
59
Why is the ATP PCr system used to provide energy for muscle contraction?
PCr is stored inside cells and this system generates ATP very quickly
60
When is the ATP-PCr system used?
During short bursts of vigorous exercise - PCr runs out after a few seconds
61
Does the ATP-PCr system require oxygen?
No - it is anaerobic but doesn't produce any lactate
62
What happens to some of the creatine in the ATP-PCr system?
Gets broken down into creatinine, which is removed from body via kidneys
63
When can creatinine levels be higher in people?
In people who exercise regularly and have high muscle mass - however could also indicate kidney damage
64
What 2 muscle fibres is skeletal muscle made up of?
Slow twitch and fast twitch
65
What are the characteristics of slow twitch muscle fibres?
They contract slowly and can work for a long time without getting tired - good for endurance activities
66
Where are high proportions of slow twitch muscle fibres found?
In muscles you use for posture
67
How is energy released in slow twitch muscle fibres?
Released slowly through aerobic respiration
68
What do slow twitch muscle fibres have a lot of?
- Mitochondria - Blood vessels to supply muscles with oxygen - Myoglobin - a red coloured protein that stores oxygen
69
Where are the mitochondria mainly found in slow twitch muscle fibres?
Near the edge so there's a short diffusion pathway for oxygen from the blood vessels to the mitochondria
70
What are characteristics of fast twitch muscle fibres?
Contract very quickly but also get tired quickly - good for short bursts of speed and power
71
Where are high proportions of fast twitch muscle fibres found?
In muscles you use for movement
72
How is energy released in fast twitch muscle fibres?
- Released quickly through anaerobic respiration using glycogen - Also have stores of PCr
73
What do fast twitch muscle fibres not have a lot of?
- Mitochondria - Blood vessels - Myoglobin - so they can't store much oxygen
74
Define details of skeletal muscle?
Striated All the muscle fibres are aligned
75
Define details of smooth muscle?
Involuntary Still has muscle fibres but not aligned - not striated
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