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Questions and Answers
Which process is associated with sarcopenia?
What leads to larger motor units in older individuals?
Which factor can attenuate ageing-related motor unit remodeling?
In ageing-related motor unit decline, what is a potential limit on physical activity's capacity?
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What is a characteristic of motor unit jitter in some diseases?
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Which age group is likely to have a higher number of motor units in the tibialis anterior muscle?
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What is one of the functional consequences of aging in relation to muscle fibers?
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Which type of fiber area increases as a result of decades of aging?
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What is a contributing factor to sarcopenia and whole muscle strength loss in aging individuals?
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Which type of muscle fibers are typically associated with slowed contractile response in older adults?
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In terms of fatiguability, which age group generally experiences less fatigue in isometric tasks according to the text?
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What is one of the factors influencing fatiguability according to the text?
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What is a possible factor contributing to sarcopenia?
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What is a characteristic of muscle weakness in old age?
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How do old adults differ from young controls in terms of muscle activation?
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Which neurotransmitter level is NOT decreased in individuals experiencing sarcopenia?
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What is a consequence of cortical hypo-excitability in the context of muscle function?
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What factors does not cause sarcopenia?
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Study Notes
Aging and Motor Unit Remodeling
- A motor unit (MU) consists of a motoneuron and the muscle fibers it innervates
- Aging leads to a decline in the number of MUs and an increase in the percentage of Type I (slow-twitch) fibers
- Collateral reinnervation: an intact MU can reinnervate fibers orphaned by the death of another MU
Functional Consequences of Aging
- Sarcopenia: age-related loss of skeletal muscle mass, strength, and power
- Slowed contractile response in older adults
- Decreased muscle strength and speed with aging
Age-Related Decline in Motor Units
- Number of MUs declines with advancing age, with an accelerated decline after 60 years
- Case study: a 92-year-old with a single MU, demonstrating denervation 5 weeks later
Motor Unit Discharge Rate
- Motor unit discharge rate (Hz) decreases with age
- Average motor unit discharge rates for different muscles (e.g., First Dorsal Interosseous, Biceps Brachii, Triceps Brachii, etc.)
Motor Unit Jitter
- Motor unit jitter is increased in some diseases and with aging compared to healthy young adults
- Assessing motor unit jitter by overlaying many action potentials and aligning based on the 1st muscle fiber
Estimates of Motor Unit Numbers
- Estimates of motor unit numbers in male tibialis anterior of young, older, and masters runners
- Number of motor units decreases with age, with some attenuation in masters athletes
Take-Home Points
- Sarcopenia is an age-related loss of skeletal muscle mass, strength, and power with central and peripheral components
- Motor unit death and collateral reinnervation lead to larger and perhaps slower motor units
- Physical activity can attenuate age-related motor unit remodeling, but may have limitations in very old age
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Description
Test your knowledge on identifying motor unit jitter in muscle fibers based on various research studies. Questions cover topics such as diseases affecting motor unit jitter, aging effects, and alignment techniques for muscle fiber action potentials.