skeletal muscle in ageing and disease Flashcards
(41 cards)
what is the relationship of the type of muscle fibre and whether or not is fatigueable easily
larger, faster muscle fibres fatigue more easily than smaller, slower muscle fibres
what is the principle of muscle malleability
muscle fibres can exist as pure type 1, pure type 2 or a mixture of the 2 - and can change during time
interventions for muscle wasting disorders need to…
- attentuate muscle atrophy
- promote muscle strength
(but NOT increase muscle fatigue)
why is giving anabolic steriods to patients with muscle wasting disease a bad idea
because despite causing an increase in the muscle bulk, it will cause increased fatigue
what is myostatin
a negative regulator of muscle mass
- causes inhibition of proliferation and differentiation of myoblasts
what are the biggest problems regarding cancer cachexia
it reduces the patients QoL and impairs responses to chemo and radiotherapy
what is critical illness myopathy
inflammatory environment sets off a cascade of signalling pathways that change the balance between synthesis and degredation of protein in favour of degredation occurring over a short period of time
what is sarcopenia
age associated loss of skeletal muscle mass and function
what causes sarcopenia
- disuse
- changing endocrine function
- chronic disease
- inflammation
- insulin resistance
- nutritional deficiency
diagnosis of sarcopenia should be considered in all older people with..
observed declines in physical function, strength or overall health
which signs are consistent with a diagnosis of sarcopenia
- gait speed of less than 1m/s
- unable to stand from a chair unassisted
- bed bound
who do you diagnose sarcopenia
low muscle mass + either low muscle strength or low physical performance
why is sarcopenia a bad thing
- gradually loose their independence
- because it puts the patient at a high risk of mortality, falls, institutionalisation and hospitalisation
what is muscle weakness
an inability to develop an initial force appropriate for the circumstances
beyond what age does the muscle strength decrease
around the age of 50
are fast or slow muscles more affected by loss of force producing capacity
fast
explain the age related motor unit remodelling
denervation of type 2 motor units –> can either lead to:
- atrophy and death of the fibes
- reinnervation by type 2 motor units to change the fibres to slow motor fibres
which type of fibre is the most susceptible to sarcopenia
type 2
what occurs before severe muscle wasting in sarcopenia
slowing of the muscle contraction
why does the slowing of muscle contraction occur
- impaired SR function? - impaired release and reuptake of Ca
- age related changes in Ca handling
what are the features of a motor end plate in someone with sarcopenia
- increase in CT
- aberrant small diameter axons
- dysmyelination
which hormone is associated with a decreased muscle mass
IGF-1
what can we do to try and slow sarcopenia
do strength training
what does strength training do for the elderly
causes significant muscle hypertrophy and increased protein turnover
- especially type 2 fibres
