Muscles in Health and Disease Flashcards
What is muscle important for
- Store for intracellular ions such as potassium and small amounts of calcium in the dissolved water
- Important for heat production
- Glucose handling
How much body weight and store of water is muscle
40% of body mass
80% of water
what are the different types of muscle
skeletal muscle/stirated
cardiac muscle
smooth muscle
what is sacromere made up of
actin and myosin
describe skeletal muscle
- stripy appearance
- nuclei in the periphery
in skeletal muscle what is central nuclei are marker of
muscle regrowth - new muscle formation
describe the nerve supply to the skeletal muscle
LMN – ventral horn of the spinal cord, exit from the ventral root, enter from the peripheral nerves, motor neurone then spreads out to innervated 5 and up to 100 or more muscle fibres
what happens when you lose a single motor neurone innervation
Affects all muscle fibres innervated by that motor neurone
- in about 2 months the muscles will atrophy
- Small angulated muscle fibres
what is a motor unit
all muscles fibres innervated by that Motor neurone
if only one single motor neurone looses its innervation what can other neurones od
Sprouting of remaining motorneuron axons synapse with denervated fibres.
Motor units enlarge and rather than been scattered they appear as groups.
What is fibre type determined by
Fibre type determined by primary motor neuron
- motor unit fibres all same fibre time
describe what happens in motor neurone disease
- In conditions where you have continuous loss of motor neurons it comes to the point where more of the motor neuornes have died and the remaining motor neurone have tried to asses the muscle fibres that are being innervated and the motor unit is larger
If that motor nuerone then dies then a lot of muscles loose innervation
what is infant hypotonia
- infants muscles are hypotonic
- get a floppy hypotonic baby
what can cause infantile hypotonia
- myopathic reason
- most of the fibres are small with a few massive hypertrophic fibres
What are the two types of infantile hypotonia
- Large type 1 muscle fibres (paler) = Slow type 1 fibres aerobic metabolism mainly
- Small type 2 muscle fibres (darker) = Fast type 2 fibres mixed aerobic and anaerobic metabolism
- Small fibres = type 1 fibres = Slow type 1 fibres aerobic metabolism mainly
- Type 2 fibres are normal to larger in diameter. = Fast type 2 fibres mixed aerobic and anaerobic metabolism
what is the good thing about infantile hypotonia
- usually sort itself out but no lasting problems
- but may not be able to do lots of exercise as they may fatigue more easily
What are the two types of skeletal muscle
Slow type 1 fibres aerobic metabolism mainly
Fast type 2 fibres mixed aerobic and anaerobic metabolism
What is sarcopenia
the loss of skeletal muscle mass and strength as a result of ageing.
How much skeletal muscle mass is lost after the age of 50 years
- 5 – 1% loss after age of 50 years
- But up to 3% - 5% if physically inactive
what happens to bone mass and muscle mass with ageing
- loss muscle mass = sarcopenia
- loose bone mass = osteoporosis
- muscle strengths is lost therefore impaired balance
- decreased bone strength
- these things contribute to fracture
What are general symptoms of muscle disorders
Pain and weakness Twitching and cramps Muscle atrophy and contractures Family history Drug exposure Endocrine disorders
How do you diagnose muscle disorders
Biopsy
EMG - electromyography
What are the two inflammatory myopathies and what is the difference
Polymyositis
Dermatomyositis (only difference is with this one you get a skin rash)
where do inflammatory myopathies start
Starts at the periphery of the muscle fascile
describe the characteristics of inflammatory myopathies
Associated with microbial infection
Autoimmune
Proximal muscle weakness (around shoulder and around the hip)
5-10 million per year
2:1 prevalence in females
40-60 years
what are the clinical features of inflammatory myopathies
Symmetrical involvement of large proximal muscles of shoulders, arms and thigh
how do you diagnose inflammatory myopathies
Serum creatine kinase elevated = marker of muscle damage
EMG
- typical irritability in 90%
Biopsy most definitive
- Variation in fibre size
- Central nuclei
- Necrosis and regeneration
- Infiltrate of inflammatory cells (lymphocytes)
What is found in the biopsy in inflammatory myopathies
Lymphocytes surround and invade individual muscle fibres (CD8+ T lymphocytes) with some macrophages to remove necrotic fibres
- damaged muscle fibres
- centrally located nuclei where there is regeneration
What does the Dermatomyositis rash look like
Dermatomyositis rash is typically purplish in colour and often
has a streaky pattern. Heliotrope
rash over eyelids with oedema
in inflammatory myopathies what antibody is found positive
ANA positive in 90% of cases
- anti-Jo1 antibody (20-40% of cases)
what is subcutaneous calcifications
Autoimmune connective tissue disease
Calcification in muscles and in skin
what is the treatment of inflammatory myopathies
Corticosteriods
- High dose 1mg/kg prednisone per day
- Maintained until creatine kinase normal
- If stopped early flares in disease and difficult to control
- Azathioprine
- Methotrexate
what is the survival rate for inflammatory myopathies
5 year survival = 80%
8 year survival = 73%
Death from malignancy, infection and pulmonary involvement
More likely if anti-Jo 1 positive
what is inclusion body myositis
- most common muscle disease of the elderly
- poor prognosis
- loss of specific muscle groups
what is the must common muscle disease of the elderly
inclusion body myositis
what is inclusion body myositis more common in
males
what is elevated in inclusion body myositis
Mild elevation in creatine kinase
what muscles are affected by inclusion body myositis
Finger and wrist flexors more than extensors and shoulder abductors
Knee extensors more than hip flexors
what problems are associated with inclusion body myositis
Associated polyneuropathy
Loss of quadriceps reflex
Dysphagia
what does the biopsy of inclusion body myositis
Fibres contain empty vacuoles and clumps
of cellular material
that contain amyloid
like material (congo red).
Filamentous inclusions of IBM
have optical properties of amyloid and contain beta amyloid, hyperphosphorylated
tau, apolipoprotein E,
presenillin 1, prion protein,
and other proteins that accumulate in muscle
give example of x linked muscular dystrophies
Duchenne and Becker muscular dystrophies
Limb girdle muscular dystrophy
Emery-Dreifuss muscular dystrophy
What are muscular dystrophies
Progressive genetically linked degenerative myopathies
- Effecting the cytoskeletal proteins that maintain the integrity of the muscle membrane and the connection with the extracellular matrix outside the cell
name some autosomal recessive muscular dystrophies
Limb girdle muscular dystrophy
Emery-Dreifuss muscular dystrophy
name some autosomal dominant muscular dystrophies
Facioscapulohumeral muscular dystrophy
Limb girdle muscular dystrophy
Emery-Dreifuss muscular dystrophy
Oculopharyngeal muscular dystrophy
name the muscle areas that are affected by
- Duchenne and Becker
- Limb Girdle
- Facto-scapulo humeral
- emery- Dreifuss
Duchenne and Becker
- arm
- plantar flexors
- thigh
Limb Girdle
- thigh
- shoulder region
Facto-scapulo humeral
- face
- shouter region
- plantar flexors
emery- Dreifuss
- shoulder and arm
- plantar flexors
What is the most common muscular dystrophy
- Duchenne muscular dystrophy is the most common
what happens in Duchenne muscular dystrophy
It is the completely loos of dysphotrin protein,
Usually connects the contractile apparatus to the ECM and maintains the integrity of the muscle membrane
How many people get Duchenne muscular dystrophy
20-30 per 100,000 males per year (1:3,500 male babies)
what muscles are affected by Duchenne muscular dystrophy
Proximal muscle weakness during first 2 years
describe duchen muscular dystrophy and its progression
Continuous slow decline
- Unable to walk by 7-12 years
- Death usually mid twenties to early thirties
- heart is affected therefore they often die from cardiomyopathy
What happens to creatine kinase in Duchenne muscular dystrophy
severely elevated
describe the biopsy of Duchenne muscular dystrophy
- Fibre size variability
- Endomysial fibrosis
- Degenerating muscle fibres undergoing myophagocytosis
- repeated degeneration and regeneration of muscle fibres therefore you end up depleting the muscle stem cells
- eventually you loose the muscle fibres and replace it with fibrotic or fat
what is Beckers disease
- Dysphotrin protein is shortened and is not as good as protecting the muscle membrane but still works
- Therefore it is milder
What is the treatment for Duchenne muscular dystrophy
- corticosteroids
what can corticosteroids induce
Type 2 fibre atrophy
- Has implications on person being able to move
- Type 1 is for posture whereas type 2 is for movement and generating force- has influence of ability of individual to move
- Take them off corticosteroids and this fibre goes back to its original size therefore the atrophy is not permanent
what can stains lead to
Approx 10% of patients
Rhabdomyolysis - myoglobin clogs the kidneys and can cause potential renal filature
how can alcohol damage the muscle
- have muscle atrophy
- Chronic - slow progressive proximal weakness
- Acute - single heavy session
What is fibromyalgia
- connective tissue disorder
- Widespread muscle pain
describe fibromyalgia diagnostic criteria
Both sides of the body, above and below waist, in axial skeleton
Combination of 11 or more of 18 specific tender points - 2kg of pressure applied
what is the trigger of fibromyalgia
Antipolymer antibodies
- 50% of patients positive
what is fibromyalgia associated with
Associated fatigue and sleep disturbance
30-60 year age group
80-90% patients female
describe the cycle of fibromyalgia
Muscle tension from daily stress leads to fatigue muscle stiffness and pain
Pain leads to poor quality of sleep
Sleep increases the stress levels and you ability to be able to cope with stress so you feel more pain and this leads round
what is the treatment of fibromyalgia
Tricyclic antidepressants
- amitriptyline
SSRIs
- fluoxetine
Exercise
Complementary therapy
