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A-level Biology AQA > 3.4.4 Skeletal Muscles as Effectors > Flashcards

3.4.4 Skeletal Muscles as Effectors Flashcards

1
Q

Muscles act as _____ and are stimulated to contract by _____

A

Muscles act as effectors and are stimulated to contract by neurones

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2
Q

What is skeletal muscle made up of?

A

Muscle fibres (large bundles of long cells)

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3
Q

What is sarcolemma?

A

Cell membrane of muscle fibre cells

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4
Q

What are transverse (T) tubules and what is their function?

A

Extensions of the sarcolemma that transmit electrical signals, to ensure that the entire muscle receives the impulse to contract simultaneously.

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5
Q

What is the sarcoplasmic reticulum?

A

specialised endoplasmic reticulum that is responsible for storing and releasing calcium ions.

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6
Q

Muscle fibres are _______ because several cells merge to form one muscle fibre.

A

Muscle fibres are multinucleate( have multiple nucleus)

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7
Q

Name 2 things muscle fibres have lots of

A
  • Mitochondria
    • Provides ATP needed for muscle contraction
  • Myofibrils (cylindrical organelles)
    • Made up of proteins and are highly specialised for contraction
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8
Q

State what 1) is

A
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9
Q

State what 2) is

A
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10
Q

State what 3) is

A
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11
Q

State what 4) is

A
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12
Q

State what 5) is

A
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13
Q

How is skeletal muscle attached to bones?

A

By tendons

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14
Q

Muscle Contraction

What do bones acts as when a pair of skeletal muscles contract and relax to move bones at a joint?

A

So act as levers, giving muscles something to pull against

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15
Q

Muscles that work together to move a bone are called ________ ____

A

antagonistic pairs

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16
Q

Muscles act in Antagonistic Pairs

State what muscle is agonist

A

Contracting muscle

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17
Q

Muscles act in Antagonistic Pairs

State what muscle is antagonist

A

Relaxing muscle

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18
Q

Describe what happens when your biceps contracts

A
  • Biceps contract (agonist), triceps relaxes (antagonist)
  • Pulls bone so your arm bends (flexes) at the elbow
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19
Q

Describe what happens when your biceps relaxes

A
  • Biceps relaxes (antagonist), triceps contracts (agonist)
  • Pulls bone so your arm straightens (extends) at the elbow
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20
Q

Myofibrils contain thick and thin ____ that ___ ___ ____ ____ to make muscles contract

A

Myofibrils contain thick and thin myofilaments that slide past each other to make muscles contract

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21
Q

What are thick myofilaments made from?

A

Protein myosin

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22
Q

What are thin myofilaments made from?

A

Protein actin

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23
Q

State what 1) is

A
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24
Q

State what 2) is

A
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25
Q

State what 3) is

A
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26
Q

State what 4) is

A
27
Q

State what 5) is

A
28
Q

State what 6) is

A
29
Q

Why do A-bands appear darker?

A

∵ contain thick myosin filaments & some overlap with actin filaments

30
Q

Why do I-bands appear lighter?

A

∵ only contain thin actin filaments

31
Q

The H-zone is the lighter region at the centre of A-band. Why is it lighter?

A

Only contains myosin filaments

32
Q

The M-line is ______ of ____ filaments

A

The M-line is middle of myosin filaments

33
Q

What is a sarcomere?

A

Distance between Z-line to Z-line

34
Q

What theory explains muscle contraction?

A

Sliding Filament Theory

35
Q

Describe the sliding filament theory

A
  • Myosin and actin filaments slide over one another to make sarcomeres contract
    • Myofilaments don’t contract
  • Simultaneous contraction of lots of sarcomeres means myofibrils and muscle fibres contract
  • Sarcomeres return to their original length as muscle relaxes
36
Q

State what happens to lengths of A-bands, I-bands, H-zones, sacromeres when sacromeres contract

A
37
Q

State what 1) is

A
38
Q

State what 2) is

A
39
Q

State what 3) is

A
40
Q

State what 4) is

A
41
Q

Describe the shape of myosin filaments’ heads

A

Have globular heads that are hinged

(Move back and forth)

42
Q

State what the 2 binding sites on a myosin head are for

A

actin & ATP

43
Q

What are the binding sites on actin filaments for & what are they called?

A
  • Myosin heads
  • Called actin-myosin binding sites
44
Q

What does tropomyosin (found between actin filaments) help to do?

A

Helps myofilaments move past each other

45
Q

In resting (unstimulated) muscle, why are actin-myosin binding sites blocked by tropomyosin?

A

So myofilaments can’t slide past each other ∵ myosin heads can’t bind actin-myosin binding site on actin filaments

46
Q

Describe how muscles contract in detail

A
  1. When action potential from motor neurone stimulates muscle cell, it depolarises sarcolemma
    1. Depolarisation spreads down T-tubules
    2. = sarcoplasmic reticulum releases Ca2+ into sarcoplasm
  2. Influx of Ca2+ causes tropomyosin molecules to more, exposing binding sites
  3. Myosin heads, have ADP attached, attach to binding site on actin, creating actin-myosin cross bridge
  4. Ca2+ activate ATPase to hydrolyse ATP to ADP
    1. Energy released causes myosin heads to bend, pulling actin filament
  5. Another ATP molecule attaches to myosin head, causing myosin to detach from actin
    1. With ADP myosin head can reattach to actin
  6. Myosin head then reattaches to different binding sites further along actin
    1. New actin-myosin cross bridge is formed & cycle is repeated
47
Q

Describe what happens when muscle stops being stimulated (i.e. when excitation stops)

A
  1. When muscle stops being stimulated, Ca2+ ions leave binding sites and moved by active transport back into sarcoplasmic reticulum
  2. Causes tropomyosin molecules to move back & block actin-myosin binding sites
  3. Muscles aren’t contracted ∵ no myosin heads are attached to actin filaments
  4. Actin filaments slide back to their relaxed position which lengthens sarcomere
48
Q

Name the 3 main ways in which ATP is continually generated for
muscle contraction

A
  1. Aerobic respiration
  2. Anaerobic respiration
  3. ATP-Phosphocreatine (PCr System)
49
Q

How is most of ATP generated in aerobic respiration?

A

via oxidative phosphorylation in mitochondria

50
Q

What type of excercise is aerobic respiration best for?

A

Long periods of low-intensity exercise

51
Q

What type of excercise is anaerobic respiration best for?

A

Short periods of hard exercise

52
Q

Why is anaerobic respiration only good for short periods of hard exercise?

A
  • ATP rapidly made by glycolysis
  • Lactate quickly builds up in muscle & = muscle fatigue
53
Q

Describe how ATP is generated from the ATP-Phosphocreatine (PCr system)

A
  • ATP is made by phosphorylating ADP
  • Adding phosphate group from PCr
54
Q

For what type of excercise is the ATP-PCr system best used for?

A

Short bursts of vigorous exercise

55
Q

Why is the ATP-PCr system best used for short bursts of vigorous exercise?

A
  • PCr is stored inside cells and ATP-PCr system generates ATP very quickly
  • PCr runs out after a few seconds
56
Q

ATP-PCr system is _____ and ____

A

ATP-PCr system is anaerobic and alactic (doesn’t form any lactate)

57
Q

How is creatine (Cr) removed from the body?

A

Creatine (Cr) gets broken down into creatinine - removed from body via kidneys

58
Q

In what types of people are creatinine levels higher in?

A

People who exercise regularly and those with high muscle mass

59
Q

What can high creatinine levels sometimes indicate?

A

Kidney damage

60
Q

Name 2 types of muscle fibres

A
  • Slow twitch
  • Fast twitch
61
Q

Different muscles have different proportions of…

A

slow and fast twitch fibres

62
Q

Name 6 differences between slow and fast twitch fibres

A
63
Q

Name 3 things fast twitch contains

A
  • High conc. of enzymes used in anaerobic respiration
  • A store of phosphocreatine
  • High concentration of glycogen
64
Q

What is used to reform phosphocreatine?

A

ATP

A-level Biology AQA (41 decks)

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