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Exercise Physiology > Muscle Structure and Function Part 1 W4 > Flashcards

Muscle Structure and Function Part 1 W4 Flashcards

1
Q

What are the functions of skeletal muscle?

A

Force production for locomotion and breathing
Force production for postural support
Heat production during cold stress
Act as an endocrine organ

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2
Q

What are flexors muscle actions?

A

Decreases joint angles

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3
Q

What are extensors muscle actions?

A

Increases joint angles

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4
Q

What is the sarcolemma?

A

Muscle cell membrane

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5
Q

What is the basement membrane?

A

Just below endomysium

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6
Q

What is the endomysium?

A

Surrounds muscle fibres

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7
Q

What is the perimysium?

A

Surrounds fascicles

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8
Q

What is the epimysium?

A

Surrounds entire muscle

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9
Q

What is the microstructure of myofibrils?

A

Contains contractile proteins:
- Actin (thin filament)
- Myosin (thick filament)

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10
Q

What is the microstructure of the sarcomere?

A

Z line
M line
H zone
A band
I band

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11
Q

What is the sarcoplasmic reticulum?

A

Storage sites for calcium
Terminal cisternae

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12
Q

What is the transverse tubules?

A

Extend from sarcolemma to sarcoplasmic reticulum

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13
Q

How does satellite cells play a key role in muscle growth and repair?

A

They increase the number of nuclei in mature muscle fibres

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14
Q

What is the myonuclear domain?

A

Volume of sarcoplasm surrounding each nucleus
Each nucleus can support a limited myonuclear domain

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15
Q

What is myonuclei and muscle hypertrophy relationship?

A

Increased myonuclei

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16
Q

What is myonuclei and muscle atrophy relationship?

A

Decreased myonuclei

17
Q

What allows for greater protein synthesis?

A

More myonuclear

18
Q

What is the neuromuscular junction?

A

Junction between motor neuron and muscle fibre

19
Q

What is the motor end plate?

A

Pocket formed around motor neuron by sarcolemma

20
Q

What is the neuromuscular cleft?

A

Short gap between neuron and muscle fibre

21
Q

What is acetylcholine?

A

Ach is a neurotransmitter released from the motor neuron
Causes an end-plate potential (EPP)
Depolarization of muscle fibre
Signal for muscle contraction

22
Q

In the sliding filament model, what causes muscle shortening to occur?

A

Movement of actin filament over the myosin filament

23
Q

What is cross-bridge formation?

A

Actin and myosin form to create a “power stroke”

24
Q

What is a repeated contraction cycle?

A

A single contraction cycle shortens the muscle by 1% of resting length
Some muscles can shorten up to 60% of resting length

25
Q

What is excitation-contraction coupling?

A

Sequence of events where nerve impulses reaches muscle membrane and leads to muscle shortening by cross-bridge activity

26
Q

What is contraction mediated by?

A

Calcium

27
Q

What is fatigue?

A

A decline in muscle power output

28
Q

What does a decline in muscle power output occur due to?

A

Decrease in muscle force production at the cross-bridge level
Decrease in muscle shortening velocity

29
Q

What are the possible causes of fatigue in heavy intensity exercise?

A

Decreased Ca2+ release from the sarcoplasmic reticulum
Accumulation of metabolites that inhibit myofilament sensitivity to Ca2+

30
Q

What are the key metabolites contributing to fatigue during heavy intensity exercise?

A

Pi, H+ and free radicals

  • Pi and free radicals modify cross-bridge head and reduce number of cross-bridges bound to actin
  • H+ ions bind to Ca2+ binding sites on troponin, preventing Ca2+ binding and contraction
31
Q

What are the possible causes of fatigue in moderate intensity exercise?

A

Increased radical production
Glycogen depletion

32
Q

What are the key metabolites contributing to fatigue?

A

Accumulation of Pi and H+ do not contribute to fatigue during moderate intensity exercise

Radical accumulation of modifies cross-bridge head and reduces number of cross-bridges bound to actin

Depletion of muscle glycogen reduces TCA cycle intermediates and decreases ATP production via oxidative phosphorylation

33
Q

What is EAMS (Exercise-associated muscle cramps)?

A

Spasmodic, Involuntary muscle contractions

34
Q

What is EAMS likely to cause in the spinal cord?

A

Hyperactive motor neurons

High-intensity exercise can alter muscle spindle and Golgi Tendon Organ function
Increased excitatory activity of muscle spindles and reduced inhibitory effect of the Golgi Tendon Organ

35
Q

What strategies can be used to alleviate EAMS?

A

Passive stretching often relieves this type of muscle cramp

Possible that activating ion channels (transient receptor potential channels) in the mouth/ throat could send inhibitory signals to the spinal cord, and thus inhibit overactive motor neurons

Exercise Physiology (24 decks)

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