Muscle

Question 1

What is sarcopenia?

Answer 1

Age-associated loss of skeletal muscle mass and function
- diagnosis should be considered in all older patients with observed declines in physical function, strength or overall health

Question 2

Define muscle weakness

Answer 2

An inability to develop an initial force appropriate for the circumstances

Question 3

What are the neural mechanisms underlying age-related motor unit remodelling?

Answer 3

Get a progressive denervation of type 2 motor units, then get a reinnervation of formerly type 2 with type 1 –> get an overall slowing of the muscle

Question 4

What is thought to be the role of the sarcoplasmic reticulum in sarcopenia?

Answer 4

Potential impaired release and reuptake of calcium

Question 5

What are the changes that could occur at the NMJ in ageing that could affect neuromuscular function?

Answer 5

• widening of the end plate
• longer nerve terminals
• fewer side branches

Question 6

What is DMD?

Answer 6

A condition with generalised muscle weakness and muscle wasting affecting limb and trunk muscles first, with calves often enlarged and elevated CK levels

• muscle fibres are broken down and replaced with fat and connective tissue
• wheelchair dependent, eventually cardiac and smooth muscle also affected
• x-linked recessive inheritance

Question 7

What are some clinical features of DMD?

Answer 7

• between 3-6 years the gait becomes lordotic and waddling
• Gowers sign
• enlargement of the calf muscles
• muscles of the lower extremity and torso appear more affected than those of upper extremity
• sparing of extra-ocular muscles

Question 8

What causes DMD?

Answer 8

Mutation in the dystrophin gene
–> deficiency in dystrophin expression, deletion in the gene causes a frame shift that results in premature mRNA translation and the synthesis of very small, unstable fragments

Question 9

What is the difference with BMD?

Answer 9

• onset later (adolescence or adulthood)
• almost identical symptoms to DMD but less severe
• significant amounts of abnormal, smaller molecules (more useful portions of dystrophin than in DMD)
• reading frame preserved

Question 10

What is the mechanism of muscle damage in DMD?

Answer 10

Damage to membranes

• disruption allows influx of calcium, get hypercontraction and necrosis
• increased serum CK

Question 11

What is the current gold standard treatment for DMD?

Answer 11

Corticosteroids

• anti-inflammatory, preservation of smaller muscle fibres
• used to counter effects of chronic inflammation and preserve existing muscle fibres

Question 12

What does BPG do?

Answer 12

Improves the pathophysiology and survival in the dko mice model

• decreased serum CK and latency to fall
• improved max SERCA activity