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EPHE 241 > Muscles II > Flashcards

Muscles II Flashcards

1
Q

Type 1 or 2: large and numerous mitochondria

A

Type 1

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2
Q

Type 1 or 2: slow rate of cross-bridge cycling

A

Type 1

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3
Q

Force generation in muscle depends on (3)

A
  1. types and number of motor units recruited
  2. initial muscle length
  3. nature of neural stimulation of motor unit
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4
Q

Define incomplete (unfused) tetanus

A

Sustained but wavering contraction

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5
Q

How is oxidative capacity increased?

A

Increased capillarization, number of mitochondria, and amount of glycolyti cenzymes

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6
Q

Weight training (increases/decreases) synchrony

A

Increases

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7
Q

How are muscle fibres typed? (4)

A
  1. muscle biopsy
  2. staining for type of myosin ATPase
  3. immunohistochemical staining
  4. gel electrophoresis
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8
Q

Type 1 or 2: Higher capacity for electrical transmission of APs

A

Type 2

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9
Q

Frequency of stimulation depends on… (3)

A
  1. simple twitch
  2. summation
  3. tetanus
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10
Q

Three characteristics in which skeletal muscle fibre types differ

A
  1. primary mechanisms to produce ATP
  2. type of motor neuron innervation
  3. type of myosin heavy chain expressed
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11
Q

Prolonged workouts result in _______ NMJ area

A

More expansive

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12
Q

Slow fibres have myosin with _____ ATPase activity

A

Slow

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13
Q

Two reasons that fast fibres exert more force than slow fibres

A
  1. max force per cross-sectional area

2. more cross-bridges per cross-sectional area

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14
Q

Fast fibres contract ____ times faster than slow fibres

A

2-3x

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15
Q

Fast fibres have myosin with ______ ATPase activity

A

Fast

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16
Q

Define isometric contraction

A

Muscle exerts force without changing length

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17
Q

Define asynchronous summation

A

During submaximal contraction, mu contract and summate asynchronously (some contract while other’s relax)

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18
Q

How does fibre composition affect fatigue?

A

Fuel availibility

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19
Q

Action potential through motor neuron causes release of ACh at _____ muscle fibres that it innervates

A

All

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20
Q

Rate limiting step of relaxation

A

Ca2+ ATPase

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21
Q

Muscle hypertrophy causes (increased/decreased) protein synthesis, statelite cell (proliferation/degredation), (less/more) and (thinner/thicker) myofibrils, (less/more) sarcomeres, and increased stores of ____, _____, ______

A

Increased; proliferation; more thicker; more; and ATP, CrP, glycogen

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22
Q

Breakdown of fibres in non-athletes (%)

A

50-50 fast and slow

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23
Q

Load changes with

A

Position of limb

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24
Q

________: increase in muscle fibre size with strength training

A

Hypertrophy

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25
Q

Central/neural causes of temporary reduction in muscular performance

A

Mechanisms including proximal (upstream) to the NMJ

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26
Q

Factors of local fatigue (3)

A

Fibre composition, failure at NMJ, failure of contractile mechanisms

27
Q

Fast fibres relax _____ times faster than slow fibres

A

10x

28
Q

Biochemical properties of muscle fibre characteristics (2)

A
  1. oxidative capacity (number of capillaries, mitochondria, myoglobin)
  2. type of myosin ATPase (speed of ATP degradation)
29
Q

As strength demand increases, we want to increase (synchrony/asynchrony)

A

Synchrony

30
Q

What is the rate limiting step of contraction cycle?

A

ATP hydrolysis

31
Q

Define complete (fused) tetanus

A

When all troponin has Ca2+ bound and crossbridge cycling is maxed out, so individual contractions can’t be measured and a smooth, max force contraction occurs

32
Q

Muscle fatigue begins when?

A

Immediately with the start of physical activity

33
Q

High fibre : nerve = _____ movements

A

Gross movements

34
Q

Type 1 or 2: well developed short-term glycolytic system

A

Type 2

35
Q

The max velocity of shortening is greatest at (highest/lowest) force

A

Lowest

36
Q

Which fibre type has highest maximal shortening velocity? I, IIa, IIx

A

IIx

37
Q

How do contractile mechanisms start to fail during fatigue?

A

Depletion of phosphagen stores, increased acidity and temp, and degradation of contractile proteins

38
Q

Two main characteristics of muscle fibre types

A
  1. biochemical properties

2. Contractile properties

39
Q

Type 1 or 2: Less well-developed glycolytic capacity (ie. less lactate dehydrogenase)

A

Type 1

40
Q

Define concentric contraction

A

Muscle shortens during force production

41
Q

At any absolute force, the speed of movement is greater in muscles with a (higher/lower) percent of fast-twitch fibres

A

Higher

42
Q

Muscle/peripheral causes of temporary reduction in muscular performance

A

Mechanisms of excitation-contraction coupling as well as metabolic accumulation

43
Q

Isotonic twitches get larger in ________ as recruited in _____ loads

A

Larger muscle fibres; larger loads

44
Q

Low fibre : nerve = ______ movements

A

Fine movements

45
Q

A fast-to-slow shift in fibre type characteristics is seen in ________ and ______ training

A

Endurance and resistance

46
Q

High intensity workouts result in ______ of synapses

A

greater dispersion

47
Q

Type 1 or 2: Rapid calcium release and reuptake by efficient SR

A

Type 2

48
Q

Contractile properties of muscle fibre contraction (3)

A
  1. maximal force production (force per unit of cross sectional area)
  2. speed of contraction (myosin ATPase activity)
  3. muscle fibre efficiency
49
Q

How does staining for type of myosin ATPase tell you which fibre type a sample is?

A

Type 1 is darkest, type 11a is lightest, and type 11x is in between

50
Q

How does immunohistochemical staining help type fibres?

A

Antibodies bind selectively to unique myosin proteins, and fibre types are differentiated by colour difference

51
Q

How does gel electrophoresis help type muscle fibres?

A

Identifies myosin isoforms specific to different fibre types

52
Q

Type 1 or 2: fatigue resistant

A

Type 1

53
Q

________: increase in muscle fibre number during strength traiinng

A

Hyperplasia

54
Q

For maximal/explosive contractions, we use (synchrony/asynchrony)

A

Synchrony

55
Q

What fibre types are more likely to exhibit failure at NMJ?

A

Type II

56
Q

Endurance training (increases/decreases) oxidative capacity

A

Increases

57
Q

Isometric twitches within a given muscle cell twitch all have _____ magnitude and shape

A

the same

58
Q

Metabolic adaptations via improved glucose transport cause…..

A

Enhanced activation of insulin signalling cascade, and increased [GLUT-4 protein]

59
Q

Increased synchrony (increases/decreases) strength without changing fibre size

A

Increases

60
Q

Type 1 or 2: generate energy for ATP synthesis via aerobic system

A

Type 1

61
Q

Type 1 or 2: high myosin ATPase activity

A

Type 2

62
Q

Define eccentric muscle contraction

A

Muscle produces force but length increases

63
Q

Hypertrophy or hyperplasia: seen in humans during strength training

A

Hypertrophy

64
Q

Faster rate of myosin ATP hydrolysis causes a faster rate of _______

A

crossbridge cycling

EPHE 241 (10 decks)

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