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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
Central/neural causes of temporary reduction in muscular performance
Mechanisms including proximal (upstream) to the NMJ
26
Factors of local fatigue (3)
Fibre composition, failure at NMJ, failure of contractile mechanisms
27
Fast fibres relax _____ times faster than slow fibres
10x
28
Biochemical properties of muscle fibre characteristics (2)
1. oxidative capacity (number of capillaries, mitochondria, myoglobin) 2. type of myosin ATPase (speed of ATP degradation)
29
As strength demand increases, we want to increase (synchrony/asynchrony)
Synchrony
30
What is the rate limiting step of contraction cycle?
ATP hydrolysis
31
Define complete (fused) tetanus
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
Muscle fatigue begins when?
Immediately with the start of physical activity
33
High fibre : nerve = _____ movements
Gross movements
34
Type 1 or 2: well developed short-term glycolytic system
Type 2
35
The max velocity of shortening is greatest at (highest/lowest) force
Lowest
36
Which fibre type has highest maximal shortening velocity? I, IIa, IIx
IIx
37
How do contractile mechanisms start to fail during fatigue?
Depletion of phosphagen stores, increased acidity and temp, and degradation of contractile proteins
38
Two main characteristics of muscle fibre types
1. biochemical properties | 2. Contractile properties
39
Type 1 or 2: Less well-developed glycolytic capacity (ie. less lactate dehydrogenase)
Type 1
40
Define concentric contraction
Muscle shortens during force production
41
At any absolute force, the speed of movement is greater in muscles with a (higher/lower) percent of fast-twitch fibres
Higher
42
Muscle/peripheral causes of temporary reduction in muscular performance
Mechanisms of excitation-contraction coupling as well as metabolic accumulation
43
Isotonic twitches get larger in ________ as recruited in _____ loads
Larger muscle fibres; larger loads
44
Low fibre : nerve = ______ movements
Fine movements
45
A fast-to-slow shift in fibre type characteristics is seen in ________ and ______ training
Endurance and resistance
46
High intensity workouts result in ______ of synapses
greater dispersion
47
Type 1 or 2: Rapid calcium release and reuptake by efficient SR
Type 2
48
Contractile properties of muscle fibre contraction (3)
1. maximal force production (force per unit of cross sectional area) 2. speed of contraction (myosin ATPase activity) 3. muscle fibre efficiency
49
How does staining for type of myosin ATPase tell you which fibre type a sample is?
Type 1 is darkest, type 11a is lightest, and type 11x is in between
50
How does immunohistochemical staining help type fibres?
Antibodies bind selectively to unique myosin proteins, and fibre types are differentiated by colour difference
51
How does gel electrophoresis help type muscle fibres?
Identifies myosin isoforms specific to different fibre types
52
Type 1 or 2: fatigue resistant
Type 1
53
________: increase in muscle fibre number during strength traiinng
Hyperplasia
54
For maximal/explosive contractions, we use (synchrony/asynchrony)
Synchrony
55
What fibre types are more likely to exhibit failure at NMJ?
Type II
56
Endurance training (increases/decreases) oxidative capacity
Increases
57
Isometric twitches within a given muscle cell twitch all have _____ magnitude and shape
the same
58
Metabolic adaptations via improved glucose transport cause.....
Enhanced activation of insulin signalling cascade, and increased [GLUT-4 protein]
59
Increased synchrony (increases/decreases) strength without changing fibre size
Increases
60
Type 1 or 2: generate energy for ATP synthesis via aerobic system
Type 1
61
Type 1 or 2: high myosin ATPase activity
Type 2
62
Define eccentric muscle contraction
Muscle produces force but length increases
63
Hypertrophy or hyperplasia: seen in humans during strength training
Hypertrophy
64
Faster rate of myosin ATP hydrolysis causes a faster rate of _______
crossbridge cycling

EPHE 241 (10 decks)

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