Lecture 34 - Ageing and skeletal muscle Flashcards Preview

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Flashcards in Lecture 34 - Ageing and skeletal muscle Deck (24):
1

What are the multifactorial causes of sarcopenia?

disuse, changing endocrine function, chronic diseases, inflammation, insulin resistance, and nutritional deficiencies

2

What is the criteria for patients to be considering to be exhibiting sarcopenia?

bedridden, can't independently rise from a chair
gait speed

3

What are the 3 criteria that define sarcopenia?

1. low muscle mass
2. low muscle strength
3. low physical performance

4

Sarcopenia is independent of?

(societal factors)

ethnicity,
disease states,
income,
health behaviours

5

drop off is greater for activities that require...

force and power

6

typically __ muscles are more affected than ___ muscles

typically fast muscles are more affected than slow muscles

7

What are the factors controlling muscle mass?

Nutritional status
hormones
genetics
innervation
inflammation
oxidative stress
blood flow
exercise (activity)
Disease
protein synthesis/degradation

8

sarcopenia is a neuromuscle syndrome, meaning...

it is concerning Motor units

there is selective de-innervation of the type to MUs

followed by reinnervation with type 1 MUs

9

What causes the selective deinnervation of fast MUs?

Two possibilities:

Loss of signals from nerves to muscles

loss of signals from muscles back to nerves

a difficult hypothesis to test - significant interplay between neural and muscular pathways

10

True of false

with sarcopenia, There is a loss of mosaic pattern of fast and slow fibre distribution

true

fibre type grouping due to selective loss of MUs

11

Before there is wasting of muscle fibres there are other changed, including:

slowing of contraction

changes in SR - impaired release and reuptake of Ca2+

age-related changes in Ca2+ handling affect speed of contraction

contributes to falls and fall-related injuries (can't quickly retain balance)

12

Summarise the motoneuron changes in aging

a loss of motoneurons with aging and a loss of numbers and diameters of motor axons in the ventral roots

some of these cease functioning (fibres may die)

other send out new axonal branches called sprouts

most susceptible MUs are those for the type IIB fibres and this loss of fast-twitch units, not surprisingly, will prolong contraction time

fast fibres reinnervate less successfully than slow fibers

fast fibres remain deinnervated or they are reinnervated by axonal sprouting from slow fibres.

The loss and atrophy of muscle fibres and the remodelling contribute to overall muscle atrophy

13

possible demyelination could affect NT, slow AP propagation. Other changes to NMJ include:

gradual changes in pre/post synaptic components, incl.

widening of end -plate
longer nerve terminals
fewer side branches

14

There is an increase in ____ in aging muscle making it more stiff

collagen

15

what are the changes in skeletal biomechanica variables with ageing muscle?

decrase max running velocity

decrease stride length

decease stride frequency

increase stride cycle time

increase braking and push off contact time

16

Summarise the cellular and molecular changes that contribute to sarcopenia

muscle fibre
satellite cells
E-c couplng
Adipocyte infiltration
mitochonria
myofilaments
fiber type transformation

muscle fibre
-decrease in number and size (predominately type II)

Satellite cells
- reduced number
- less response to injury

E-c couplng
- disruption/uncoupling
-deficits in Ca2+ release

Adipocyte infiltration
- increase inter and intra muscular adipose tissue

mitochondria
- reduced number
- loss of enzyme content

myofilaments
- reuced single fibre maximal force
- reduction in myosin protein content and function
- reduction in elasticity

fiber type transformation
- fast to slow fibre type shift

17

what happens to sports performance with ageing?

elite status does not protect msucle from gradual losses in fibres/MUs

loss of power a concern for athletes

injuries are more common

most elite athletes begin to show some decine in performance by their 30s

18

what are the problems facing older champions?

diminishing muscle mass

progressive decrease in size of type II fobres

declining VO2 MAX
stiffening connective tissue

19

What can we do to intervene against sarcopenia?

we must attempt to conserve muscle strength for both the prevention and reversal of age-related changes

this can be facilitated by the incorporation of strength training

20

Strength training in the eldery can be effective at adressing...

increase muscle strength, total body mass and muscle fibre area

significant fibre hypertrophy

21

true or false

the strength training adaptations in elderly are likely to result from a combination of neural adaptations and muscle hypertrophy

but we must face the fact that loss of msucle mass is inevitable

true

strength training must be a lifelong commitment if it is to be a preventative measure

22

what are the relevant hormonal changes with ageing

decreased circulating levels of anabolic hormones contribute to changes in muscle size and strength

hormones include: GH, IGF-1, testosterone

compromises efficiency of muscle regeneration as a consequence of daily ''wear and tear''

23

what are the therapeutic approaches for combating sarcopenia

exercise - strength training

protein supplements

hormonal - GH, testosterone precursors, selective androgen receptor modulators

24

true or false

exercise can slow the rate which the sarcopenia changes occur - therefore exercise is very important

true

but there are practical considerations: is high-intensity strength training suitable for most adults, some maybe not.