18 - Muscle in Health and Disease Flashcards
What percent of body mass should be muscle
40%
80% of water
Muscle function
Movement and strenght
Heat production
Glucose metabolism
Store for intracellular ions
Features of skeletal muscle
Striated
Multinucleated fibres
Peripheral nucleus
What is the significance of central nuclei in skeletal muscle
The muscle is going through repair
What is a motor unit
Functional unit of a group of muscle fibres that will all contract at the same time
What happens if loss of innervation in adult of single motor neuron
all muscle fibres innervated by that motor neuron are affected – muscle undergoes atrophy
What is infantile hypotonia
Floppy baby sydrome - baby with decreased tone which can be caused by many reasons
What would you look at if suspect a myopathic hypotonia
ATPase
Size of fibres
What is congenital fibre type disproportion
Disproportion in different types of fibres
t1 - large type 1 muscle fibres (aerobic) with t2 - small t2 muscle fibres (mixed)
can also have the opposite
Usually evens out
Sarcopenia
Muscle is lost and replaced by fat
More likely to have osteoporosis
percentage of muscle loss after the age of 50
0.5 - 1%
3-5% if physically inactive
What is the difference between polymyositis and dermatomyositis
They are the exact same however dermatomyositis includes skin involvement(rash)
What is dermatomyositis
An autoimmune condition causing proximal muscle weakness (hip and shoulders)
Biopsy of dermatomyositis pation
The outer part of the fascicle there is invasion of inflammatory cells (CD8 T lymphocytes)
Variation in fibre size
Central nuclei
Macrophages
Clinical features of dermatomyositis
Symmetrical
Serum creatinine kinase elevated
EMG of patient with dermatomyositis
Typically irritable in 90%
- looks like the muscle is always active
Fibrillations at rest + spontaneous activity
What does the rash look like in dermatomyositis
Purple
Streaky pattern
Heliotrope rash over eyelids, cheek, back with oedema
What is the autoantibody that is present in 20-40% of dermatomyositis cases
Anti-Jo1 antibody
Golgi apparatus antibody
What does the Anti-Jo1 antibody cause
Subcutaneous calcification in muscles and in skin
Treatment of dermatomyositis
Corticosteroids - maintained until creatinine kinase is normal (high dose prednisone)
Azathioprine
Methotrexate
What is Inclusion body myositis
Inflammatory myopathy causing muscle weakness
Which muscles affected in inclusion body myositis
Finger and wrist flexors
Knee extensors
Loss of quadriceps reflex
Dysphagia
Biopsy of inclusion body myositis
Fibres contain empty vacuoles + clumps of cellular material that contain amyloid like material - stains with congo red
What do the filamentous inclusion contain
Beta amyloid
Hyperphosphorylated tau
apolipprotein E
presenillin E
What is duchenne syndrome
Complete loss of dystrophin
What is becker syndrome
A milder form of duchennes
What is dystrophins funciton
Acts as a shock absorber, prevents muscle fibres being damaged
When does the symptoms of duchennes present
Proximal muscle weakness for up to 2 years
Continuous slow decline
Unable to walk by 7-12 years
Death mid 20s to 30s
Creatine kinase levels in duchennes
Elevated massively
Biopsy of duchennes
Fibre size variability
Endomysial fibrosis
Loss of muscle replaced with fibrotic material and fat
What can long term corticosteroids do to muscle
type 2 fibre atrophy
What can statins cause
rhabdomyolysis
What is fibromyalgia
Pain in the fibrous tissue of muscle - widespread muscle pain
Where does fibromyalgia occur in the body
Both sides of body
above and below the waist
How do you diagnose fibromyalgia
Combination of 11 or more out of 18 tender points
Cycle of fibromyalgia issues
Pain Muscle tension Daily stress Limited activity Fatigue Depression Muscle stiffness
Common groups with fibromyalgia
30-60 y/o
80-90% are female
Treatment for fibromyalgia
Tricyclic depressants for sleep - amitriptyline
SSRIS also for sleep - fluoxetine
Exercise
Complementary therapy
