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KNSS 202: Exercise Physiology > Chapter 1 > Flashcards

Flashcards in Chapter 1 Deck (82):
1

Name and describe the 3 types of muscle tissue.

- Smooth muscle: involuntary, hollow organs
- Cardiac muscle: involuntary, heart
- Skeletal muscle: voluntary, skeleton

2

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

- epimysium
- fasciculi

3

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

- perimysium
- muscle fibres

4

Muscle fiber is surrounded by ______ and consists of ______.

- endomysium
- myofibrils divided into sarcomeres

5

Name the 5 parts of muscle fibres.

- plasmalemma
- satellite cells
- sarcoplasm
- transverse tubules (t tubules)
- sarcoplasmic reticulum (SR)

6

Describe the plasmalemma (cell membrane).

- Fuses with tendon
- Conducts action potential
- Maintains pH, transports nutrients

7

Describe satellite cells.

- Muscle growth, development
- Response to injury, immobilization, training

8

Describe the sarcoplasm.

- Cytoplasm of muscle cell
- Unique features: glycogen storage, myoglobin

9

Describe t tubules.

- Extensions of plasmalemma
- Carry action potential deep into muscle fiber

10

Describe the SR.

Ca2+ storage

11

Describe myofibrils.

- Muscle --> fasciculi --> muscle fiber --> myofibril
- Hundreds to thousands per muscle fiber

12

Describe sarcomeres.

- Basic contractile element of skeletal muscle
- End to end for full myofibril length

13

Myosin is _____ filament.

thick

14

What does myosin look like?

Two intertwined filaments with globular heads

15

Describe the globular heads on myosin.

- Protrude 360° from thick filament axis
- Will interact with actin filaments for contraction

16

Myosin is stabilized by _____.

titin

17

Actin is ______ filament.

thin

18

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

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

19

Actin is anchored at ______.

Z-disk

20

Actin is equally spaced out by ______.

titin

21

_____ _____ innervate muscle fibres.

α-motor neurons

22

A motor unit consists of:

Single α-motor neuron + all fibers it innervates

23

More operating motor units =

more contractile force

24

What is the neuromuscular junction?

Site of communication between neuron and muscle

25

What does the neuromuscular junction consist of?

synapse between α-motor neuron and muscle fiber

26

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

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

27

The sliding filament theory is a process of ...

actin-myosin contraction

28

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

- No actin-myosin interaction at binding site
- Myofilaments overlap a little

29

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

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

30

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

- Myosin detaches from active site
- Myosin head rotates back to original position
- Myosin attaches to another active site farther down

31

The sliding filament theory process continues until:

- Z-disk reaches myosin filaments or
- AP stops, Ca2+ gets pumped back into SR

32

Energy for muscle contraction comes from:

Adenosine triphosphate (ATP)

33

ATP binds to ______ for muscle contraction.

- Binds to myosin head
- ATPase on myosin head

34

ATP =

ADP + Pi + energy

35

When does muscle relaxation occur?

AP ends, electrical stimulation of SR stops

36

What happens to Ca2+ during muscle relaxation?

- Ca2+ pumped back into SR
- Stored until next AP arrives
- Requires ATP

37

Without Ca2+, what happens to troponin and tropomyosin?

- returns to resting conformation
- Covers myosin-binding site
- Prevents actin-myosin cross-bridging

38

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

50%

39

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

- 110 ms
- slow twitch

40

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

25%

41

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

25%

42

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

- 50 ms
- fast twitch

43

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

- speed of myosin ATPase varies
- muscle biopsy
- gel electrophoresis
- SR
- motor units

44

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

- Fast myosin ATPase = fast contraction cycling
- Slower myosin ATPase = slower contraction cycling

45

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

- Small (10-100 g) piece of muscle removed
- Frozen, sliced, examined under microscope

46

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

- Type I versus II fibers have different types of myosin
- Separates different types of myosin by size

47

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

- Type II fibers have a more highly developed SR
- Faster Ca2+ release, 3 to 5 times faster Vo

48

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

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

49

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

- oxidative capacity: high
- glycolytic capacity: low
- contractile speed: slow
- fatigue resistance: high
- motor unit strength: low

50

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

- oxidative capacity: moderately high
- glycolytic capacity: high
- contractile speed: fast
- fatigue resistance: moderate
- motor unit strength: high

51

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

- oxidative capacity: low
- glycolytic capacity: highest
- contractile speed: fast
- fatigue resistance: low
- motor unit strength: high

52

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

- Each person has different ratios
- Arm and leg ratios are similar in one person
- Soleus: type I in everyone

53

Endurance athletes predominantly have what muscle fibre type?

type I

54

Power athletes predominantly have what muscle fibre type?

type II

55

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.

- 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

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.

- 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

Describe type I fibres during exercise.

- high aerobic endurance
- efficiently produce ATP from fat, carbohydrate

58

Type I fibres have high aerobic endurance, meaning:

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

59

Describe type II fibres in general during exercise.

- Poor aerobic endurance, fatigue quickly
- Produce ATP anaerobically

60

Describe type IIa fibres during exercise.

- More force, faster fatigue than type I
- Short, high-intensity endurance events (1,600 m run)

61

Describe type IIx fibres during exercise.

- Seldom used for everyday activities
- Short, explosive sprints (100 m)

62

Name 3 fibre type determinants.

- genetic factors
- training factors
- aging

63

Describe how genetic factors can influence fibre type determinants.

- Determine which α-motor neurons innervate fibers
- Fibers differentiate based on α-motor neuron

64

Describe how training factors can influence fibre type determinants.

- Endurance versus strength training, detraining
- Can induce small (10%) change in fiber type

65

Describe how aging can influence fibre type determinants.

muscles lose type II motor units

66

Muscle fibre recruitment is also called ...

motor unit recruitment

67

Less force production means...

fewer or smaller motor units

68

More force production means...

more or larger motor units

69

Type ___ motor units smaller than type _____.

type I smaller than type II

70

What is the recruitment order for muscle fibre types?

- Smallest (type I) motor units recruited first
- Midsized (type IIa) motor units recruited next
- Largest (type IIx) motor units recruited last

71

What is the size principle?

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

72

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

- cardiovascular function
- motivation
- training habits
- muscle size

73

Name the 2 types of muscle contraction.

- static (isometric contraction)
- dynamic contraction

74

Describe static (isometric) contraction.

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

75

Describe dynamic contraction.

- Muscle produces force and changes length
- Joint movement produced

76

What are the 2 subtypes of dynamic contraction?

- concentric contraction
- eccentric contraction

77

Describe concentric contraction.

- Muscle shortens while producing force
- Most familiar type of contraction
- Sarcomere shortens, filaments slide toward center

78

Describe eccentric contraction.

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

79

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

- type I motor units: less force
- type II motor units: more force

80

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

- twitch: 1 stimulation
- summation: 3 stimuli
- tetanus: continual stimulation

81

Describe the length-tension relationship.

- Optimal sarcomere length = optimal overlap
- Too short or too stretched = little or no force develops

82

Describe the speed-force relationship.

- Concentric: maximal force development decreases at higher speeds
- Eccentric: maximal force development increases at higher speeds