Week 4 - Muscle Ageing Flashcards

1
Q

Define sarcopenia.

A

age related loss of muscle mass

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2
Q

In reference to sarcopenia, answer the following.
- When does muscle mass begin to decline?
- What age does the slow phase of age-related muscle decline range from?
- By age 80, what % of total muscle mass can be lost?

A
  • 25
  • 25-50 years
  • 50%
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3
Q

Is strength loss greater in lower or upper body with ageing?

A

Lower body - 40% decline
Upper body - 33% decline

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4
Q

Relationship between muscle power and ageing.

A

Muscle power decreases with age

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5
Q

What underlies the functional declines (loss in muscle strength) with age?

A

1) A loss of muscle mass (fiber loss and atrophy)
2) Muscle quality is reduced
3) Neuromuscular alterations

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6
Q

What is the average rate of muscle mass loss after 40 years old? What about after 70 years old?

A
  • 8% per decade to 70 years old
  • 15% per decade
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7
Q

Is there a greater muscle mass loss relative to body mass in men or women?

A

Men

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8
Q

What muscle fiber atrophies faster with age, type I or type II?

A

type II

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9
Q

What is greater, losses in muscle strength or losses in muscle mass?

A

losses in muscle strength are far greater than muscle mass loss

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10
Q

How is muscle quality reduced with age?

A

Increase in subcutaneous and intermuscular fat, and less muscle.
Increased non-contractile material.

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11
Q

How does neuromuscular alterations explain loss in muscle strength as we age?

A

Aging results in motor unit loss which results in muscle fibers (predominantly type II) becoming denervated which causes muscle fiber atrophy or fiber loss.

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12
Q

Denervation and reinnervation of muscle fibers

A
  • Loss of motor neurons leaves fibers denervated.
    This results:
  • Type II fiber loss
  • Type II fiber atrophy due to less innervation (lower motor unit firing frequency)
  • OR reinnervation of fibers by type I motor units.
  • When fibers are reinnervated by other motor units this creates larger motor units that are less efficient.
  • Denervation without reinnervation results in type II fiber loss.
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13
Q

What are the two options for denervated muscle fibers when we have the loss of motor units?

A

1) Atrophy and loss
2) Atrophy and reinnervation

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14
Q

How does denervation and collateral re-innervation alter muscle characteristics?

A
  • Increased co-expression of myosin isoforms
  • Decreased force output
  • Decreased velocity of contraction and hence power
  • Altered fatigue resistance
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15
Q

The effect of reinnervation of fibers

A
  • Increased size of motor units (make them less efficient)
  • Preserves some muscle mass
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16
Q

Why may fatigue resistance increase in old age?

A

Type II fibers innervated by type I motor units with age and so they behave more like type I fibers with a higher fatigue resistance. However, they produce less force.

17
Q

What is disease-related muscle wasting termed?

A

cachexia