LEWIS: Muscles Flashcards Preview

A2 PE > LEWIS: Muscles > Flashcards

Flashcards in LEWIS: Muscles Deck (74):
0

Each muscle fibre contains:

-myofibrils
-mitochondria
-sarcoplasmic reticulum
-nuclei

1

Sarcolemma is the

Plasma membrane

2

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

Calcium ions that when released initiate muscle contraction

3

Sarcoplasm is the

Liquor interior of a muscle fibre

4

Striated appearance or muscles is caused by alternating

Dark and light bands

5

Dark bands are called

A bands

6

Light bands are called

I bands

7

The I bands are bisected by the

Z line

8

The centre of A bands is divided by the

H zone

9

The reoccurring unit in a Myofibril is the

Sarcomere

10

The sarcomere goes from

One Z line to another

11

2 myofilaments:

Actin
Myosin

12

Actin filament is the

Thin, light band

13

The thin filament of actin extends in each direction from the

Z line

14

Myosin filament produces the

Dark, thick band

15

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

Muscle fibre of which it is a part

16

Where the myofilaments do not overlap is known as the

H zone

17

Step 1 of muscle contraction:

1) nerve impulse arrives at the end of motor neurone

18

Step 2 of muscle contraction:

2) acetylcholine is released

19

Step 3 of muscle contraction:

-acetylcholine binds to receptors on motor end plates

20

Step 4 of muscle contractions:

-sodium ions rush into muscle fibres

21

Step 5 of muscle contractions:

Muscle action potential sweeps into T tubules

22

Step 6 of muscle contractions:

-sarcoplasmic reticulum releases calcium ions

23

Step 7 of muscle contraction

Calcium binds to troponin, causing it to change shape

24

Step 8 of muscle contraction

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

25

Step 9 of muscle contraction

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

26

Step 10 of muscle contraction

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

27

Step 11 of muscle contraction:

-myosin releases from actin

28

Step 12 of muscle contraction:

Myosin re-extends into 'ready' position

29

As a muscle contracts:

-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

Muscle is stretched:

-width of I bands and H zones increases
-no change in the width of A bands

31

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

Tropomyosin

32

muscular contraction is controlled by:

proprioceptors
muscle spindle apparatus
golgi tendon organs

33

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

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

34

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

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

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

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

3 types of muscle fibre:

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

37

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

genetically determined

38

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

one particular unit

39

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

more fast-twitch

40

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

continuous v weight

41

Capillary density:
TYPE I
TYPE IIa
TYPE IIb


high
medium
low

42

Aerobic capacity:
TYPE I
TYPE IIa
TYPE IIb


high
medium
low

43

Anaerobic capacity:
TYPE I
TYPE IIa
TYPE IIb


Low
medium
high

44

Fatigue levels:
TYPE I
TYPE IIa
TYPE IIb


low
medium
high

45

Myoglobin levels:
TYPE I
TYPE IIa
TYPE IIb


high
medium
low

46

Glycogen levels:
TYPE I
TYPE IIa
TYPE IIb


low
high
high

47

Triglyceride levels:
TYPE I
TYPE IIa
TYPE IIb


high
medium
low

48

Contraction speed:
TYPE I
TYPE IIa
TYPE IIb


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

49

Mitochondrial density:
TYPE I
TYPE IIa
TYPE IIb


high
medium
low

50

A bands =

both actin and myosin

51

I bands =

actin only

52

H zones =

myosin only

53

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

stays the same

54

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

prolonged exercise

55

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

Aerobic energy pathways

56

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

anaerobic energy pathways

57

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

phosphocreatine

58

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

1 mile run/400m swim

59

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

100m sprints/50m swims

60

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

physical - length of lever, VO2 max, physique
psychological - motivation, commitment, confidence

61

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

neuromuscular junction

62

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

motor unit

63

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

all-or-nothing law

64

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

partial contraction

65

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

occur

66

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

occur

67

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

recruitment
frequency
timing

68

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

force that can be produced



multiple summation

69

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

wave summation

70

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

summation

71

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

number and size of motor units involved

72

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

spatial summation

73

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

strength exerted by the muscle