W29-L3,4: Skeletal muscle and ageing Flashcards
In the slowest contracting are there fast twitch fibres?
Yes
What are the goal of interventions to attenuate muscle wasting?
- attenuate muscle atrophy
* promote muscle strength
What is myostatin and what does knocking it out cause?
myostatin is a “negative regulator” of muscle mass and knocking out causes increase of muscle mass
What is disuse muscle atrophy?
when the muscle is not used eg loss of gravity which upsets balance of synthesis vs degradation
What is seen in muscle wasting in the ICU?
significant inflammation which upsets balance of synthesis and degradation, disruption of architecture and atrophy of muscle
What is sarcopenia?
age-associated loss of skeletal muscle mass and function
What is used for the diagnosis of sarcopenia?
- low muscle mass
- low muscle strength
- low physical performance
What type of muscle activity declines the fastest?
muscle activity that
requires explosive contraction
What is muscle weakness?
an inability to develop an initial force appropriate for the circumstances
Beyond what age is there a steep drop in muscle strength?
50
Which muscles are more protected from sarcopenia?
Slower muscles
What happens to fibres that lose their innervation?
They atrophy
What can re-innervation of muscles fibres cause?
Causes them to change from fast to slow fibres
When does slowing of contraction occur?
Occurs before severe muscle wasting
Are there neural changes in sacropenia?
Yes, not just muscle effects
How does connective tissue within muscle change with advancing age?
Become stiffened because they loose their elasticity due to increased connective tissue
Are the effects of ageing on muscle reversible?
No, but they can be attenuated
Are older muscles still responsive to interventions like strength training?
Yes
What is the onset of Duchenne muscular dystrophy?
About 2-6 years old
What are the symptoms of Duchenne muscular dystrophy?
Generalised weakness and often enlarged calves
What is the progression of Duchenne muscular dystrophy?
Progresses slowly but survival is rare beyond late twenties
What is the inheritance of Duchenne muscular dystrophy?
X linked recessive
What is gowers sign?
Have to walk themselves up to stand up
What causes Duchenne muscular dystrophy?
mutation in the dystrophin gene which causes deficiency in dystrophin expression (usually complete absence)
What is the role of dystrophin?
cytoskeletal protein that holds the fibres in place
What is the dystrophin-glycoprotein complex?
shock absorber that helps transmits forces
What is onset of becker muscular dystrophy?
adolescence or adulthood
What are the symptoms of becker muscular dystrophy?
Almost identical to duchenne but much less severe
What is the progression of becker muscular dystrophy?
Slowly, survival into mid to late adulthood
What is inheritance of becker muscular dystrophy?
X-linked recessive
What is the cause of becker muscular dystrophy?
Significant amounts of abnormal smaller dystrophin molecules
How is Ca+ associated with dystophin?
loss of integrity of the membrane causes increased intracellular
Ca, which activates proteases that breaks down muscle
What are some possible treatments for muscular dystrophy?
- correction of genetic defect
- Cell therapy (eg stem cell)
- pharmacological therapies to prevent symptoms
