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Exercise & Environment > Structural properties and activation of muscle > Flashcards

Structural properties and activation of muscle Flashcards

1
Q

muscle’s prime function

A

convert chemical energy stored in ATP bonds into mechanical work

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2
Q

functions of muscle

A
  • movement
  • maintain posture when sitting and standing
  • breathe, talk, eat
  • hold body structures together
  • act as a brake to slow movements
  • source of heat
  • dynamic metabolic store
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3
Q

muscoskeletal system

A

muscle, bone and connective tissue

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4
Q

how much of human is muscoskeletal system

A

~75% lean body mass of health person

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5
Q

major component of muscle

A

water - 75%!

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6
Q

20% of muscle is

A

protein

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7
Q

5% of muscle is

A

inorganic salts and other substances

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8
Q

muscle is comprised of

A

water 75%
protein 20%
5% inorganic salts and other

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9
Q

types of protein in muscle

A

1000s of different proteins.
40% is myosin
20% is actin
rest is other proteins including tropomyosin

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10
Q

epimysium

A

connective tissue around the muscle that holds structure

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11
Q

connective tissue around the muscle that holds structure

A

epimysium

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12
Q

what are myofibrils made up of

A

triations of sarcomas

sarcomas are the basic contractile unit

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13
Q

what are sarcomas

A

basic contractile unit

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14
Q

what is the basic contractile unit

A

sarcomas

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15
Q

composition of sarcomere

A

limits - dark bands
thick filaments - myosin
thin filaments - actin

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16
Q

thin filaments

A

actin

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17
Q

thick filaments

A

myosin

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18
Q

myosin

A

thick filaments of sarcomere

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19
Q

actin

A

thin filaments of sarcomere

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20
Q

how do the actin and myosin interact (brief)

A

sliding of the myosin head

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21
Q

key feature of filaments

A

they are not fixed so sarcomeres can shorten and contract

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22
Q

name of muscle fibre response to one electrical pulse

A

twitch

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23
Q

what causes an isometric twitch

A

it is a mechanical response to a single electrical response

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24
Q

Pt

A

max force peak twitch

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25
Q

EMD

A

electrical mechanical delay

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26
Q

TPT

A

time to peak tension

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27
Q

1/2RT

A

1/2 relaxation time

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28
Q

how many phases of a twitch, and what’s the difference

A

2
1st phase is fast
2nd phase is slow

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29
Q

what differs the response of fibre to electrical pulse

A

fibre type; slow or fast

fatigue

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30
Q

events of propagation of an action potential

A
  • AP travels down t-tubule
  • AP activates the sarcoplasmic reticulum
  • SPR is open to release ca2+
  • ca2+ binds to thin filament/actin
  • myosin then binds to action
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31
Q

knowing events of propagation helps with what

A

knowing where problem is for targeting drug treatment

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32
Q

when are events of propagation disturbed

A

fatigue and disease

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33
Q

response to many electrical pulses

A

tetanus

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34
Q

tetanus

A

response to many electrical pulses

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35
Q

difference between twitch and tetanus

A 
twitch = one electrical pulse
tetanus = many electrical pulses
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36
Q

what happens when there is little to no gap between stimuli of muscle fibres

A

there is no time for relaxation, causing pulses to become fused

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37
Q

when do pulses become fused

A

when there is not enough time between multiple stimuli for relaxation

38
Q

how long does half removal of calcium take

A

~80ms = long time

39
Q

what happens at 10Hz

A

concentration of calcium builds, leading to partially fused tetanus

40
Q

at what stimuli frequency does tetanus begin to fuse and why

A

10Hz, because the concentration of calcium starts to build

41
Q

what does high rate of impulses cause high levels of

A

calcium in the cytoplasms

this interrupts cross-bridge cycling

42
Q

what effect does consistently high levels of calcium in cytoplasm do

A

permits cross bridge cycling

43
Q

what interrupts cross-bridge cycling

A

high rate of impulses which causes consistently high levels of calcium in the cytoplasm

44
Q

functions of sarcomeres in series

A
  • sprinter
  • high velocity
  • low force
45
Q

function of sarcomeres in parallel

A
  • body builder
  • low velocity
  • high force
46
Q

in what contraction does muscle fibre length not change

A

isometric

47
Q

in what contraction does muscle fibre shorten

A

concentric

48
Q

isometric contraction

A
  • myosin bound to actin
  • myosin try to push action
  • overall length of muscle doesn’t change
    e. g holding a heavy load
49
Q

concentric contraction

A
  • myosin bound to actin
  • myosin successfully push actin
  • sarcomere shorting occurs
  • muscle length shortens
    e. g lifting a heavy load
50
Q

high force low velocity

A

isometric contraction

51
Q

low force high velocity

A

concentric contraction

52
Q

when is force maximum

A

when velocity is zero

53
Q

what is force when velocity is zero

A

force is maximum

54
Q

power equation

A

power = force x velocity

55
Q

how do force, power and velocity link

A

power = force x velocity

56
Q

why can force not be produced with great velocity

A

when going fast, only a small proportion of myosin heads can attach

57
Q

during which contractions can power be measured

A

concentric, not isometric

?

58
Q

what athlete would have muscles in parallel

A

body builder

59
Q

what athlete would have muscles in series

A

sprinter

60
Q

what produces more power; muscles in series or parallel

A

both produce equal power!

  • parallel = low velocity, high force
  • series = high velocity, low force
61
Q

factors of parallel power

A
  • force adds up
  • each elements feels only part of whole force
  • movements do not add up
  • each element experiences whole movement
62
Q

factors of series power

A
  • forces do not add up
  • each element feels whole force
  • movements do add up
  • movement is shared between elements
63
Q

defining fibre type for slow and fast twitch fibres

A

composition of myosin heavy chain isoform

64
Q

how many types of myosin heavy chain

A

3

Type 1, Type 2a, Type 2x

65
Q

What are the types of myosin heavy chain

A

Type 1, slow
Type 2a, fast
Type 2x fast

66
Q

myosin heavy chains for fast twitch

A

type 2a

type 2 x

67
Q

myosin heavy chains for slow twitch

A

typa 1

68
Q

what myosin heavy chain has peak isometric force at 110ms

A

type 1

69
Q

what myosin heavy chain has peak isometric force at 50ms

A

type 2a

70
Q

when is peak isometric force for type 1 myosin heavy chain

A

110ms (slow)

71
Q

when is peak isometric force for type 2a myosin heavy chain

A

50ms (fast)

72
Q

what athlete has more type 1 myosin heavy chain

A

endurance athelte

73
Q

what athletes have more type 2 myosin heavy chain

A

sprinters

74
Q

what comprises a motor unit

A

a single motor neurone and all the muscle fibres that it innervates

75
Q

how many muscle fibres does one motor neurone innervate

A

varies! some less than 10, some over 2,000

76
Q

example of muscle that has few motor units

A

gastrocnemius

big muscle that needs to be efficient and so has few neurons that innervate lots of fibres

77
Q

example of muscle with lots of motor units

A

extraocular muscles need to react quickly with fine tuning. Lots of neurons in charge of few fibres each

78
Q

neural mechanisms responsible for muscle fibre recruitment

A
  • spatial recruitment

- temporal recruitment

79
Q

another term for muscle fibre recruitment

A

motor unit recruitment

80
Q

spatial recruitment

A

for big muscles, legs

  • recruit the minimum number of motor units needed
  • smallest type I recruited first
  • mid sized type IIa recruited next
  • largest type IIx recruits last
81
Q

what is the principle of spacial recruitment

A

Size/ Henneman principle

82
Q

temporal recruitment

A

for fine and fast adjustment; eyes

  • rate coding refers to the motor unit firing rate
  • frequency
  • active motor units can discharge at higher frequencies to generate greater tensions
  • smaller muscles rely more on rate coding
  • larger muscles of mixed fibre rely more on recruitment
83
Q

wha affects whole muscle activation

A
  • muscle arcitecture
  • antagonist co-contraction
  • neural activation
  • temperature
  • fibre type
  • hormones
84
Q

muscle architecture that affects activation

A

physiological cross-sectional area = PSCA
anatomical cross-sectional area = ACSA
- angle of pennation

85
Q

variables of neural activation for muscles

A
  • recruitment
  • firing rate
  • motor unit synchronisation
86
Q

angle of pinnation

A

ideally muscles would have nicely arranged fibres for maximum force output
in reality, most have pinnation angles
pinnation angles give different force direction causing complicated transmission of force

87
Q

how to measure ACSA

A 
accurate: magnetic resonance image
less accurate:
- computerised topography
- ultra sound b-mode
- tape measure & skin fold
- tape measure
88
Q

relating muscle force to tendon force

A

muscle force =

tendon force/cos(pennation angle)

89
Q

antagonist co-contraction

A

when one muscle contracts, the other relaxes
- antagonist muscle acts as brake, producing small but sufficient force to brake as needed and reduce eternal force of agonist

90
Q

net force equation

A

force of agonist - force of antagonist

91
Q

is myosin activation muscle activation

A

yes, but not solely! lots of other factors involved and needed to understand exercise and disease

Exercise & Environment (14 decks)

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