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Exercise Physiology > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

Subsarcolemmal mitochondria purpose

A

Produce cellular energy needed to maintain active transport of ions across the sarcolemma

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2
Q

Intermyofibrillar mitochondria purpose

A

Provides energy to sustain muscle contraction

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3
Q

Where is the subsarcolemmal mitochondria located

A

Directly beneath the cell membrane

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4
Q

Where is the intermyofibrillar mitochondria located

A

Near the myofibrillar (contractile) proteins

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5
Q

5 components of muscles

A

Muscle —> fascicle —> muscle fibers —> myofibrils —> sarcomere

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6
Q

Thin filament

A

Actin

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7
Q

Thick filament

A

Myosin

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8
Q

Satellite cells

A

Produce more muscle fibers through myoblasts

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9
Q

How do satellite cells aid in muscle growth and repair

A

They increase the number of nuclei to allow for greater protein synthesis

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10
Q

Hypertrophy

A

Increase in muscle size by adding muscle fibers

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11
Q

Result of going from trained to untrained

A

Increased amount of nuclei remains even though the muscle is smaller. Allows for hypertrophy to happen faster

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12
Q

3 basic functions of skeletal muscles

A
  1. locomotion and breathing 2. Postural support 3. Heat production during cold stress
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13
Q

How is the muscle considered an endocrine gland?

A

Skeletal muscle produces myokines during contractions

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14
Q

Myokines role in glucose

A

Stimulate glucose uptake and promote liver glucose production

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15
Q

Myokines role in fat

A

Stimulate fatty acid oxidation and triglyceride breakdown

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16
Q

Myokines role in blood vessels

A

They promote blood vessel growth in the muscle

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17
Q

Interleukin 6 (IL-6)

A

Pro-inflammatory and anti-inflammatory; Produced during exercise and promotes anti-inflammatory effects.

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18
Q

Static muscle movement

A

Muscle exerts force without changing length (isometric)

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19
Q

Concentric

A

Muscle shortened during force production

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20
Q

Eccentric

A

Muscle lengthens during force production (results in soreness typically)

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21
Q

Somatic nervous system

A

Responsible for controlling skeletal muscle

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22
Q

Somatic motor neurons role

A

Carry neural messages from spinal cord to skeletal muscles

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23
Q

Neuromuscular junction

A

Connection point between motor neuron and muscle fiber

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24
Q

Motor end plate

A

Pocket around motor neurons by sarcolemma

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25
Q

How does muscle shortening occur

A

From movement of thin actin filament over thick myosin filament forming cross-bridges

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26
Q

What happens to the z line during muscle contraction

A

As the sarcomere shortens, the distance between the spines of the sarcomere shorten

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27
Q

During a biceps curl, what shortens within the biceps brachii sarcomeres

A

the h zone and the I band

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28
Q

What remains the same in a muscle contraction

A

The m line, the a zone

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29
Q

Where does the energy for muscle contraction come from?

A

Myosin ATPase breaks down ATP as fiber contracts. This releases ADP and Phosphate with energy

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30
Q

5 steps of excitation coupling

A
  1. Action potential stimulates Ach at neuromuscular junction
  2. Ach induces action potential in muscle fiber down t tubule
  3. Action potential releases Ca2+ from SR
  4. Ca2+ initiates troop myosin displacement to reveal myosin binding sites
  5. Myosin forms cross bridges with actin producing force
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31
Q

What does calcium bind to in the muscle

A

The troponin

32
Q

What happens when calcium binds to troponin

A

Tropomyosin moves revealing binding site

33
Q

What type of exercise are muscle cramps associated with?

A

Prolonged high intensity

34
Q

Electrolyte depletion and dehydration theory

A

Sweating increases water and sodium loss which causes muscle cramps. More likely in hot environment

35
Q

What are limitations to the electrolyte depletion and dehydration theory on muscle cramps?

A

It doesn’t explain for how cramps are localized

36
Q

Neuromuscular control theory

A

Abnormal spinal reflex activity due to fatigue

37
Q

How does fatigue cause abnormal spinal reflex activity

A

increased excitatory activity of muscle spindles and reduced inhibitory effect of golgi tendon organ

38
Q

Muscle spindle role

A

Detect stretch of the muscle

39
Q

Golgi tendon organ role

A

Causes muscle to relax

40
Q

How does passive stretching relieve muscle cramps

A

Activated the golgi tendon organ to inhibit motor neurons in the spinal cord resulting in muscle relaxation

41
Q

TRP channels

A

When activated, send inhibitory signals to the spinal cord to inhibit overactive motor neurons that cause cramping

42
Q

4 steps of muscle spindle activity

A
  1. Spindle detect stretch
  2. Sensory neurons send AP to spinal cord
  3. Sensory neurons synapse with alpha motor neurons
  4. Stimulation of alpha motor neurons causes the muscles to contract and resist being stretched
43
Q

Type 1 fibers

A

Slow twitch fibers; oxidative fibers

44
Q

Type IIa fibers

A

Immediate fibers; fast-oxidative glycolytic fibers

45
Q

Type IIx

A

Fast twitch fibers; fast-glycolytic fibers

46
Q

Which fibers have the most mitochondria

A

Slow type I fibers> type IIa> type IIx

47
Q

Which fibers are most resistent to fatigue

A

Slow type 1> type IIa > type IIx

48
Q

Predominant energy system for Type I fibers

A

Aerobic

49
Q

Predominant energy system to type IIa fibers

A

Combo in aerobic and anaerobic

50
Q

Predominant energy system for type IIx fibers

A

Anaerobic

51
Q

Increased number of capillaries means

A

More oxygen and blood delivered to muscle fibers

52
Q

Mitochondria is associated with

A

Oxygen to generate ATP. More mitochondria means more oxidative slower to fatigue type 1 fibers

53
Q

What delivers oxygen to mitochondria

A

Myoglobin

54
Q

Which fibers break down ATP the fastest?

A

Fast fibers break down ATP faster and have higher ATPace activity
Type IIx> Type IIa> Type I

55
Q

What is the speed of contraction (Vmax) dependent on?

A

Myosin ATPase activity. The faster the sarcoplasmic reticulum releases Ca2+ will increase ATPase activity. Fast fibers are more efficient at this

56
Q

Why do larger muscle fibers produce more force

A

They have more actin and myosin than small fibers do.

57
Q

Which muscle fiber types have the greatest speed

A

Type IIx > type IIa > type I due to size

58
Q

Power in relation to muscle contraction

A

Power = force x shortening velocity
Fast fibers have a higher shortening velocity and greater force due to size and number of actin and myosins

59
Q

Which muscle fibers are more efficient at generating force

A

Fast fibers use more ATP to generate force than slow type I fibers do so they are less efficient

60
Q

Type of fibers in power athletes

A

Higher % of fast fibers

61
Q

Fiber type in endurance athletes

A

Higher % in slow fibers

62
Q

What amount of motor units produce more force

A

The more motor units recruited, the more force generated

63
Q

What motor unit speed generates greater force?

A

Faster motor units

64
Q

Type s motor units

A

the smallest of the motor neurons; innervate type 1(slow) muscle fibers

65
Q

Type FR motor units

A

(Fatigue resistant) innervate type IIa muscle fibers

66
Q

Type FF motor units

A

(Fast , fatiguable) Largest motor unit; innervate type IIx muscle fibers

67
Q

What is the motor unit recruitment pattern during graded exercise

A

Type s —> type Fr —> type FF

68
Q

What is the muscle fiber type recruitment pattern in graded exercise

A

Type I —> type IIa —> type IIx

69
Q

How does increasing stimulus produce more force

A

Increasing stimulus (increasing weight) recruits more motor units

70
Q

What muscle length produces the most force

A

Whichever length has the ability for the most cross bridge formations

71
Q

Why is force production additive

A

Increases Ca2+ availability allows for more contraction coupling

72
Q

Why can’t we assume muscle soreness is a result of Lactic acid?

A

Lactate removal happens within 60 minutes post exercise and soreness doesn’t always result after repetitive training

73
Q

Delayed onset muscle soreness

A

24-48 hrs post; microscopic teases in muscle fibers or connective tissues; eeccentric

74
Q

What is responsible for soreness within hours

A

Sarcomere damage

75
Q

What is responsible for soreness following days

A

Immune cell infiltration

76
Q

What is responsible for soreness days to weeks post exercise

A

Satellite cell activation causing hypertorphy

77
Q

6 steps of DOMS

A
  1. Structural damage to muscle fibers
  2. Membrane damage
  3. Calcium leaks out of SR
  4. Cellular breakdown of proteins
  5. Inflammatory response
  6. Edema and pain

Exercise Physiology (12 decks)

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