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A2 PE > LEWIS: Muscles > Flashcards

LEWIS: Muscles Flashcards

0
Q

Sarcolemma is the

A

Plasma membrane

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1
Q

Each muscle fibre contains:

A
  • myofibrils
  • mitochondria
  • sarcoplasmic reticulum
  • nuclei
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2
Q

Sarcoplasmic reticulum is the equivalent to the endoplasmic reticulum of cells. It forms a network of channels - acts as a store of

A

Calcium ions that when released initiate muscle contraction

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3
Q

Sarcoplasm is the

A

Liquor interior of a muscle fibre

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4
Q

Striated appearance or muscles is caused by alternating

A

Dark and light bands

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5
Q

Dark bands are called

A

A bands

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6
Q

Light bands are called

A

I bands

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7
Q

The I bands are bisected by the

A

Z line

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8
Q

The centre of A bands is divided by the

A

H zone

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9
Q

The reoccurring unit in a Myofibril is the

A

Sarcomere

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10
Q

The sarcomere goes from

A

One Z line to another

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11
Q

2 myofilaments:

A

Actin

Myosin

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12
Q

Actin filament is the

A

Thin, light band

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13
Q

The thin filament of actin extends in each direction from the

A

Z line

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14
Q

Myosin filament produces the

A

Dark, thick band

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15
Q

Shortening of the sarcomeres in a Myofibril produces the shortening of the Myofibril and in turn, of the

A

Muscle fibre of which it is a part

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16
Q

Where the myofilaments do not overlap is known as the

A

H zone

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17
Q

Step 1 of muscle contraction:

A

1) nerve impulse arrives at the end of motor neurone

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18
Q

Step 2 of muscle contraction:

A

2) acetylcholine is released

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19
Q

Step 3 of muscle contraction:

A

-acetylcholine binds to receptors on motor end plates

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20
Q

Step 4 of muscle contractions:

A

-sodium ions rush into muscle fibres

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21
Q

Step 5 of muscle contractions:

A

Muscle action potential sweeps into T tubules

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22
Q

Step 6 of muscle contractions:

A

-sarcoplasmic reticulum releases calcium ions

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23
Q

Step 7 of muscle contraction

A

Calcium binds to troponin, causing it to change shape

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24
Q

Step 8 of muscle contraction

A

When calcium binds to troponin, it causes tropomyosin to move and expose myosin binding site

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25
Q

Step 9 of muscle contraction

A
  • myosin binds to actin, activating enzyme myosin-ATPase (energy released from ATP breakdown = causes change in shape of myosin head)
  • cross bridge formed
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26
Q

Step 10 of muscle contraction

A

-Myosin pivots pulling actin filaments (ratchet mechanism/power stroke)

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27
Q

Step 11 of muscle contraction:

A

-myosin releases from actin

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28
Q

Step 12 of muscle contraction:

A

Myosin re-extends into ‘ready’ position

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29
Q

As a muscle contracts:

A
  • Z lines come closer together
  • width of the I bands decreases
  • width of the H zones decreases
  • no change in width of A bands
30
Q

Muscle is stretched:

A
  • width of I bands and H zones increases

- no change in the width of A bands

31
Q

At rest, thick myosin heads are prevented from attaching to the thin actin filament due to

A

Tropomyosin

32
Q

muscular contraction is controlled by:

A

proprioceptors
muscle spindle apparatus
golgi tendon organs

33
Q

proprioceptors are sense organs in the muscles, tendons and joints that

A

inform the body of the extent of movement that has taken place

34
Q

Muscle spindle apparatus are very sensitive proprioceptors that lie between skeletal muscle fibres and provide information about the

A

rate of change in muscle length - if muscle is stretched too far they alter tension to shorten muscle, causing a stretch reflex which automatically shortens the muscle

35
Q

Golgi tendon organs are thin pockets of connective tissue that occur where the muscle fibre and tendon meet. They provide information to the CNS concerning the

A

stretch within the muscle
stretched they trigger the reflex inhibition of the muscle that is contracting and stretching the tendon, and the reflex inhibition of the muscle that is contracting and stretching the tendon, and the reflex contraction of the antagonist

36
Q

3 types of muscle fibre:

A

type I - slow oxidative
type IIa - fast oxidative glycolytic
type IIb - fast glycolytic

37
Q

Skeletal muscles contain all 3 types of muscle fibre but not in equal proportions. the mix is mainly

A

genetically determined

38
Q

Muscle fibres are grouped into motor units and only one type of fibre can be found in

A

one particular unit

39
Q

The relative proportion of each fibre type varies in the same muscles of different people. E.g. an endurance athlete will have a greater proportion of slow twitch fibres in the leg muscles than an elite sprinter who will have

A

more fast-twitch

40
Q

Training is a way the body can produce adaptations to the proportions of muscle fibres:

A

continuous v weight

41
Q

Capillary density:
TYPE I
TYPE IIa
TYPE IIb

A

high
medium
low

42
Q

Aerobic capacity:
TYPE I
TYPE IIa
TYPE IIb

A

high
medium
low

43
Q

Anaerobic capacity:
TYPE I
TYPE IIa
TYPE IIb

A

Low
medium
high

44
Q

Fatigue levels:
TYPE I
TYPE IIa
TYPE IIb

A

low
medium
high

45
Q

Myoglobin levels:
TYPE I
TYPE IIa
TYPE IIb

A

high
medium
low

46
Q

Glycogen levels:
TYPE I
TYPE IIa
TYPE IIb

A

low
high
high

47
Q

Triglyceride levels:
TYPE I
TYPE IIa
TYPE IIb

A

high
medium
low

48
Q

Contraction speed:
TYPE I
TYPE IIa
TYPE IIb

A

slow (10)
fast (50)
fast (50)

49
Q

Mitochondrial density:
TYPE I
TYPE IIa
TYPE IIb

A

high
medium
low

50
Q

A bands =

A

both actin and myosin

51
Q

I bands =

A

actin only

52
Q

H zones =

A

myosin only

53
Q

Muscle contracts, Z lines move closer together, the width of the I bands and H zones decreases while the A band

A

stays the same

54
Q

Slow twitch fibres tend to be smaller in size and produce less overall force than fast-twitch, and they are more energy efficient, producing more force for the same energy input, therefore are well adapted for

A

prolonged exercise

55
Q

Slow twitch = high endurance levels and are suited to aerobic exercise. Produce ATP primarily from

A

Aerobic energy pathways

56
Q

fast twitch better suited to anaerobic activity, as they produce their ATP primarily from

A

anaerobic energy pathways

57
Q

fast twitch are well adapted to short, intense burst of effort. Large diameter as there are more myosin filaments - able to produce more force.
Due to more complex arrangement of sarcoplasmic reticulum, calcium ions can be released and returned to storage more quickly than in slow twitch. Also possess a different myosin-ATPase which releases ATP quicker than than slow twitch.
Fast twitch also have larger stores of

A

phosphocreatine

58
Q

FOG fibres fatigue easily because of their limited endurance. Used mainly for short, high-intensity endurance events, e.g.

A

1 mile run/400m swim

59
Q

FG primarily used in low intensity exercise or highly explosive events:

A

100m sprints/50m swims

60
Q

presence of high proportion of slow-twitch and fast-twitch fibres is not the sole determinant of good performance. likely other factors must influence:

A

physical - length of lever, VO2 max, physique

psychological - motivation, commitment, confidence

61
Q

motor neurones leading to skeletal muscles have branches, each of which meets a muscle fibre at a

A

neuromuscular junction

62
Q

nerve impulses passing down a single motor neurone will thus trigger contraction in all the muscle fibres at which the branches of that neurone end. This minimum unit of contraction is called a

A

motor unit

63
Q

Each muscle fibre within a motor unit either contracts or does not contract - this is the

A

all-or-nothing law

64
Q

The all or nothing law states that muscle fibres either contract or do not contract. There is no such thing as a

A

partial contraction

65
Q

If an impulse is equal to or more than the threshold (minimum amount of stimulation required to start a contraction) then the muscle action will

66
Q

If the impulse is less than the threshold then no muscle action will

67
Q

Gradation of contraction refers to the strength or force exerted by a muscle and is dependent on:

A

recruitment
frequency
timing

68
Q

Recruitment: the greater the number of motor units that are recruited, the greater the number of muscle fibres that will contract. This increases the

More motor units also referred to as

Which units we use, depending on whether they are fast or slow twitch will affect the force

A

force that can be produced

multiple summation

69
Q

Frequency: the greater the frequency of stimuli the greater the tension developed by the muscle.
Stimuli occur very infrequently, the calcium concentration in the sarcomere returns to resting levels before the arrival of the next stimulus.
When the stimuli occur frequently, not all the calcium released in response to the first stimulation is taken back into the sarcoplasmic reticulum, as a result summation occurs - also called

A

wave summation

70
Q

wave summation, where repeated activation of a motor neurone stimulating a given muscle fibre results in

71
Q

spatial summation is changes in strength of contraction are brought about by altering the

A

number and size of motor units involved

72
Q

Timing: if all the motor units are stimulated at the same time, then maximum force can be applied. This is referred to as

A

spatial summation

73
Q

spatial summation, occurs when several impulses from different neurones all arrive at the same time, therefore increasing the

A

strength exerted by the muscle

A2 PE (27 decks)

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