Chapter 22 - Skeletal Muscle Flashcards
two types of skeletal muscle fibers
I: slow-twitch (endurance)
II: fast-twitch (power)
myotrauma
injury to muscle or tendon (strain) –stretching or tearing
symptoms of muscle strain
pain
redness or bruising
limited mobility
muscle weakness
how do skeletal muscles repair themselves?
satellite cells
how long does it usually take for muscle strains to heal?
8-10 weeks
myalgia
muscle pain
muscle tests
-biopsy
-electromyography (action potential)
-lab tests (creatine kinase) *increased levels indicate muscle disorder
myopathic vs. neurogenic
myopathic: muscle is affected
neuropathic: motor neuron affected
myopathy
muscle fibers don’t function for any one of many reasons – results in muscle weakness
acquired myopathy :
muscle weakness from:
infections
inflammation
endocrine/metabolic
alcohol
hereditary/genetic myopathy:
muscle weakness from:
mutations in genes coding for parts of a muscle
inflammatory myopathy
muscle weakness from inflammation from another disease
muscular dystrophies
group of disorders that cause degeneration of skeletal muscle fibers
is muscular dystrophy myopathic or neuropathic
myopathic
what are skeletal muscle fibers replaced by in muscular dystrophy disorders?
fat and fibrous tissue
where do muscular dystrophies typically occur?
extremities, shoulders, and heart – can lead to paralysis
most common type of muscular dystrophy
Duchenne (X-linked, recessive)
is duchenne muscular dystrophy more common in men or women?
men
a mutation in a gene that encodes ____ is the cause for duchenne MD
dystrophin
when do manifestations of duchenne MD begin?
3 years old; loss of ambulation between 8-12
main manifestation of duchenne MD?
enlarged calves (pseudo-hypertrophy); it’s not muscle, but fat and scar tissue
-slow motor development
-progressive wewkness
-clumsy, fall a lot
-sitting and standing difficult
life span of someone with Duchenne MD
12-20; die from respiratory insufficiency or pneumonia
chronic inflammatory myopathy symptoms
-progressive muscle weakness
-elevated CK levels
-systemic inflammation (CRP)
types of chronic inflammatory myopathy
polymyositis: muscle only; lymphocyte infiltration
dermatomyositis: rash of eyelids, face, upper chest
metabolic myopathy
metabolic disease causing muscle weakness
McArdle’s Disease
autosomal recessive disease that is a defect of myophosphorylase (break down glycogen) *glycogen storage disease
symptoms of McArdle’s disease
exercise intolerance
painful muscle cramps
myoglobinuria
rhabdomyolysis
dissolving of skeletal muscle
etiology of rhabdomyolysis
damaged skeletal muscle cells leak myoglobin and K+ into plasma which is filtered through the glomerulus and cause orange/brown urine color
complications of rhabdomyolysis
nephrotoxicity - acute renal failure
tubular obstruction
third spacing
fluid sequestration in damaged tissue –> dehydration –> decreased blood flow to kidneys
what is myasthenia gravis
autoimmune disease failure of neuromuscular transmission//connection (nerve cell can’t connect to muscle correctly)
etiology of myasthenia gravis
blockage and destruction of acetylcholine receptors
what is myasthenia gravis characterized by?
muscled weakness that is aggravated by repeated contraction
which muscle is typically affected with myasthenia gravis?
muscle with small motor units – ocular muscles
can progress to facial muscles, limbs, and respiratory system
diagnostic testing of myasthenia gravis
tensilon test
EMG
serum assay
treatment for myasthenia gravis
-immunosuppressives, cholinesterase inhibitors
-thymectomy
rhabdomyoma
rare BENIGN tumor of striated muscle
rhadomyosarcoma
rare malignant tumor of striated muscle; more common in head, neck; more common in children
paralysis types
flaccid: reduced muscle tone; lower motor neuron
spastic: over toned muscle, hyperirritable nerves
quadriplegia (tetra)
above 1st thoracic; all 4 limbs
paraplegia
below 1st thoracic; legs
hemiplegia
one sided paralysis
hemiparesis
one sided weakness
