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KNSS 202: Exercise Physiology > Chapter 1 > Flashcards

Chapter 1 Flashcards

1
Q

Name and describe the 3 types of muscle tissue.

A
  • Smooth muscle: involuntary, hollow organs
  • Cardiac muscle: involuntary, heart
  • Skeletal muscle: voluntary, skeleton
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2
Q

The entire muscle is surrounded by _____ and consists of many bundles called _____.

A
  • epimysium

- fasciculi

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3
Q

Fasciculi is surrounded by ______ and consists of individual muscle cells called _____.

A
  • perimysium

- muscle fibres

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4
Q

Muscle fiber is surrounded by ______ and consists of ______.

A
  • endomysium

- myofibrils divided into sarcomeres

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5
Q

Name the 5 parts of muscle fibres.

A
  • plasmalemma
  • satellite cells
  • sarcoplasm
  • transverse tubules (t tubules)
  • sarcoplasmic reticulum (SR)
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6
Q

Describe the plasmalemma (cell membrane).

A
  • Fuses with tendon
  • Conducts action potential
  • Maintains pH, transports nutrients
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7
Q

Describe satellite cells.

A
  • Muscle growth, development

- Response to injury, immobilization, training

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8
Q

Describe the sarcoplasm.

A
  • Cytoplasm of muscle cell

- Unique features: glycogen storage, myoglobin

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9
Q

Describe t tubules.

A
  • Extensions of plasmalemma

- Carry action potential deep into muscle fiber

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10
Q

Describe the SR.

A

Ca2+ storage

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11
Q

Describe myofibrils.

A
  • Muscle –> fasciculi –> muscle fiber –> myofibril

- Hundreds to thousands per muscle fiber

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12
Q

Describe sarcomeres.

A
  • Basic contractile element of skeletal muscle

- End to end for full myofibril length

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13
Q

Myosin is _____ filament.

A

thick

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14
Q

What does myosin look like?

A

Two intertwined filaments with globular heads

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15
Q

Describe the globular heads on myosin.

A
  • Protrude 360° from thick filament axis

- Will interact with actin filaments for contraction

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16
Q

Myosin is stabilized by _____.

A

titin

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17
Q

Actin is ______ filament.

A

thin

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18
Q

Actin is composed of 3 proteins. Name and describe them.

A
  • Actin: contains myosin-binding site
  • Tropomyosin: covers active site at rest
  • Troponin: anchored to actin, moves tropomyosin
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19
Q

Actin is anchored at ______.

A

Z-disk

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20
Q

Actin is equally spaced out by ______.

A

titin

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21
Q

_____ _____ innervate muscle fibres.

A

α-motor neurons

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22
Q

A motor unit consists of:

A

Single α-motor neuron + all fibers it innervates

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23
Q

More operating motor units =

A

more contractile force

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24
Q

What is the neuromuscular junction?

A

Site of communication between neuron and muscle

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25
Q

What does the neuromuscular junction consist of?

A

synapse between α-motor neuron and muscle fiber

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26
Q

Name and describe the steps in muscle fibre contraction: excitation-contraction coupling.

A
  1. Action potential (AP) starts in brain
  2. AP arrives at axon terminal, releases acetylcholine (ACh)
  3. ACh crosses synapse, binds to ACh receptors on plasmalemma
  4. AP travels down plasmalemma, T-tubules
  5. Triggers Ca2+ release from sarcoplasmic reticulum (SR)
  6. Ca2+ enables actin-myosin contraction
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27
Q

The sliding filament theory is a process of …

A

actin-myosin contraction

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28
Q

Describe what is happening during the relaxed state of the sliding filament theory.

A
  • No actin-myosin interaction at binding site

- Myofilaments overlap a little

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29
Q

Describe what is happening during the contracted state of the sliding filament theory.

A
  • Myosin head pulls actin toward sarcomere center (power stroke)
  • Filaments slide past each other
  • Sarcomeres, myofibrils, muscle fiber all shorten
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30
Q

Describe what is happening after the power stroke ends in the sliding filament theory.

A
  • Myosin detaches from active site
  • Myosin head rotates back to original position
  • Myosin attaches to another active site farther down
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31
Q

The sliding filament theory process continues until:

A
  • Z-disk reaches myosin filaments or

- AP stops, Ca2+ gets pumped back into SR

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32
Q

Energy for muscle contraction comes from:

A

Adenosine triphosphate (ATP)

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33
Q

ATP binds to ______ for muscle contraction.

A
  • Binds to myosin head

- ATPase on myosin head

34
Q

ATP =

A

ADP + Pi + energy

35
Q

When does muscle relaxation occur?

A

AP ends, electrical stimulation of SR stops

36
Q

What happens to Ca2+ during muscle relaxation?

A
  • Ca2+ pumped back into SR
  • Stored until next AP arrives
  • Requires ATP
37
Q

Without Ca2+, what happens to troponin and tropomyosin?

A
  • returns to resting conformation
  • Covers myosin-binding site
  • Prevents actin-myosin cross-bridging
38
Q

The average muscle consists of roughly ___% of type I fibres

A

50%

39
Q

For type I muscle fibres, peak tension is in _____ ms.

A
  • 110 ms

- slow twitch

40
Q

The average muscle consists of roughly ___% of type IIa fibres

A

25%

41
Q

The average muscle consists of roughly ___% of type IIx fibres

A

25%

42
Q

For type II muscle fibres, peak tension is in ____ ms.

A
  • 50 ms

- fast twitch

43
Q

What are the 5 ways in that type I muscle fibres differ from type II muscle fibres?

A
  • speed of myosin ATPase varies
  • muscle biopsy
  • gel electrophoresis
  • SR
  • motor units
44
Q

Describe how the speed of myosin ATPase varies between type I and type II muscle fibres.

A
  • Fast myosin ATPase = fast contraction cycling

- Slower myosin ATPase = slower contraction cycling

45
Q

Describe how muscle biopsy can be used to tell the difference between type I and type II muscle fibres.

A
  • Small (10-100 g) piece of muscle removed

- Frozen, sliced, examined under microscope

46
Q

Describe how gel electrophoresis can be used to tell the difference between type I and type II muscle fibres.

A
  • Type I versus II fibers have different types of myosin

- Separates different types of myosin by size

47
Q

Describe how the SR is different between type I and type II muscle fibres.

A
  • Type II fibers have a more highly developed SR

- Faster Ca2+ release, 3 to 5 times faster Vo

48
Q

Describe how motor units differ between type I and type II muscle fibres.

A
  • Type I motor unit: smaller neuron, <300 fibers

- Type II motor unit: larger neuron, >300 fibers

49
Q

Describe the following for type I muscle fibres: oxidative capacity, glycolytic capacity, contractile speed, fatigue resistance, motor unit strength.

A
  • oxidative capacity: high
  • glycolytic capacity: low
  • contractile speed: slow
  • fatigue resistance: high
  • motor unit strength: low
50
Q

Describe the following for type IIa muscle fibres: oxidative capacity, glycolytic capacity, contractile speed, fatigue resistance, motor unit strength.

A
  • oxidative capacity: moderately high
  • glycolytic capacity: high
  • contractile speed: fast
  • fatigue resistance: moderate
  • motor unit strength: high
51
Q

Describe the following for type IIx muscle fibres: oxidative capacity, glycolytic capacity, contractile speed, fatigue resistance, motor unit strength.

A
  • oxidative capacity: low
  • glycolytic capacity: highest
  • contractile speed: fast
  • fatigue resistance: low
  • motor unit strength: high
52
Q

Describe the distribution of fibre types (type I : type II ratios).

A
  • Each person has different ratios
  • Arm and leg ratios are similar in one person
  • Soleus: type I in everyone
53
Q

Endurance athletes predominantly have what muscle fibre type?

A

type I

54
Q

Power athletes predominantly have what muscle fibre type?

A

type II

55
Q

Describe the following for type I muscle fibres: fibres per motor neuron, motor neuron size, motor neuron conduction velocity, contraction speed (ms), type of myosin ATPase, SR development.

A
  • fibres per motor neuron: < or equal to 300
  • motor neuron size: smaller
  • motor neuron conduction velocity: slower
  • contraction speed (ms): 110
  • type of myosin ATPase: slow
  • SR development: low
56
Q

Describe the following for type II muscle fibres: fibres per motor neuron, motor neuron size, motor neuron conduction velocity, contraction speed (ms), type of myosin ATPase, SR development.

A
  • fibres per motor neuron: > or equal to 300
  • motor neuron size: larger
  • motor neuron conduction velocity: faster
  • contraction speed (ms): 50
  • type of myosin ATPase: fast
  • SR development: high
57
Q

Describe type I fibres during exercise.

A
  • high aerobic endurance

- efficiently produce ATP from fat, carbohydrate

58
Q

Type I fibres have high aerobic endurance, meaning:

A
  • Can maintain exercise for prolonged periods
  • Require oxygen for ATP production
  • Low-intensity aerobic exercise, daily activities
59
Q

Describe type II fibres in general during exercise.

A
  • Poor aerobic endurance, fatigue quickly

- Produce ATP anaerobically

60
Q

Describe type IIa fibres during exercise.

A
  • More force, faster fatigue than type I

- Short, high-intensity endurance events (1,600 m run)

61
Q

Describe type IIx fibres during exercise.

A
  • Seldom used for everyday activities

- Short, explosive sprints (100 m)

62
Q

Name 3 fibre type determinants.

A
  • genetic factors
  • training factors
  • aging
63
Q

Describe how genetic factors can influence fibre type determinants.

A
  • Determine which α-motor neurons innervate fibers

- Fibers differentiate based on α-motor neuron

64
Q

Describe how training factors can influence fibre type determinants.

A
  • Endurance versus strength training, detraining

- Can induce small (10%) change in fiber type

65
Q

Describe how aging can influence fibre type determinants.

A

muscles lose type II motor units

66
Q

Muscle fibre recruitment is also called …

A

motor unit recruitment

67
Q

Less force production means…

A

fewer or smaller motor units

68
Q

More force production means…

A

more or larger motor units

69
Q

Type ___ motor units smaller than type _____.

A

type I smaller than type II

70
Q

What is the recruitment order for muscle fibre types?

A
  • Smallest (type I) motor units recruited first
  • Midsized (type IIa) motor units recruited next
  • Largest (type IIx) motor units recruited last
71
Q

What is the size principle?

A

order of recruitment of motor units directly related to size of α-motor neuron

72
Q

Name factors (other than muscle fibre type) that can be a predictor of success.

A
  • cardiovascular function
  • motivation
  • training habits
  • muscle size
73
Q

Name the 2 types of muscle contraction.

A
  • static (isometric contraction)

- dynamic contraction

74
Q

Describe static (isometric) contraction.

A
  • Muscle produces force but does not change length
  • Joint angle does not change
  • Myosin cross-bridges form and recycle, no sliding
75
Q

Describe dynamic contraction.

A
  • Muscle produces force and changes length

- Joint movement produced

76
Q

What are the 2 subtypes of dynamic contraction?

A
  • concentric contraction

- eccentric contraction

77
Q

Describe concentric contraction.

A
  • Muscle shortens while producing force
  • Most familiar type of contraction
  • Sarcomere shortens, filaments slide toward center
78
Q

Describe eccentric contraction.

A
  • Muscle lengthens while producing force
  • Cross-bridges form but sarcomere lengthens
  • Example: lowering heavy weight
79
Q

Describe the generation of force in different types of motor units.

A
  • type I motor units: less force

- type II motor units: more force

80
Q

What are the 3 words used to describe the frequency of stimulation (rate coding)? Describe them.

A
  • twitch: 1 stimulation
  • summation: 3 stimuli
  • tetanus: continual stimulation
81
Q

Describe the length-tension relationship.

A
  • Optimal sarcomere length = optimal overlap

- Too short or too stretched = little or no force develops

82
Q

Describe the speed-force relationship.

A
  • Concentric: maximal force development decreases at higher speeds
  • Eccentric: maximal force development increases at higher speeds

KNSS 202: Exercise Physiology (4 decks)

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