Healthy aging Flashcards
what is the relationship between age and average speed
linear relationship
- as age increases, average speed decreases
- motor performance declines with age
what is the main part of the aging of the motor system
reduction in the number of motor neurons
what is caused by the reduction in motor neurons
larger amplitude in EMG due to remodelling process that results in greater proportion of large MUs
why is there a shift to the large MUs
as MN declines, the muscle fibres they innervated either die or get innervated by a branch of another MN
(causes shift towards larger MUs)
(large survives a bit longer than small)
what is sarcopenia
general reduction in muscle mass
- remodelling of the motor pool ends up in sarcopenia because some muscle fibres get deprived of innervation and are lost
where is there the most atrophy and why
larger atrophy effect in the lower limbs compared to the upper limbs
- lots of activity is done in the lower limbs and that declines the most through aging
why do men lose more compared to women
larger shift in anabolic hormones
(larger decreases in testosterone with age)
what is the difference in loss between different fibre types
loss of muscle is smallest for the type 1 fibres
20% loss compared to ~40% for other types
larger MUs kept and slow fibres kept (usually don’t go together)
what is the difference in muscle force in older muscle
older MUs fire at lower rates
older muscles have slower twitch contractions
older adults develop torque in their muscles at a slower rate
maximal rate of contraction drops by around 50%
longer interval between the first APs to muscle
what is lost during sensory system aging
40% loss of both hair cell receptors and vestibular nerve fibres
- hair cells die first and then nerve is lost after lack of activity
- loss of hair cells is continuous
what happens to the VOR gain during sensory aging
slightly reduced due to central gain enhancement
- CNS has “turned up the volume” on the remaining receptors to have the same output while making up for the lost receptors
what happens to the VSR during sensory aging
central gain enhancement seen
- older adults have a higher response to lower frequency (0-5Hz) and lower response to higher frequencies
(assessed using SVS)
why do older adults respond better to lower frequencies
because they are the frequencies of head mvmt that occur naturally
(physiological range of head mvmts)
what happens to perceptual sensitivity to head rotations and translations
reduced sensitivity
harder to differentiate between right, and left, and no rotation
what is central gain enhancement used for in perceptual sensitivity
done for the frequencies important/common in daily life
used to decrease threshold within the physiological range in order to increase the “volume” where important
