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muscles A+P CH.7 lecture 4 (Duchenne Muscular Dystrophy (genetic,…
muscles A+P CH.7 lecture 4
each muscle cell are long fibers know as muscle fibers
muscle fibers encased in a cell membrane called sarcolemma and has functional units called myofibrils
sarcomeres
functional contractile units of each fiber (thick and thin filaments)
thick
made of protein myosin
thin
made up of protein actin
actin and myosin filaments arranged in repeating units separated from eachother by dark bands called Z-lines (give striated appearance to skeletal muscle)
Z-lines
give striated appearance to skeletal muscle
border each sarcomere
contractions
causes to types of myofilaments to slide toward and shorten each sarcomere (entire muscle)
requires cross-bridges formed between myosin and actin that pull sarcomeres together
ATP and calcium
need for muscle contraction and relaxation
ATP energy helps the myosin heads form and break with actin
when muscle is relaxed, calcium is stored away from the actin and myosin in the sarcoplasmic reticulum
when we use muscle, calcium is realeased from the sarcoplasmic reticulum and causes actin, myosin, and ATP to interact causing contraction
then calcium returns to sarcoplasmic reticulum, cross-bridge is broken and muscle relaxes
ACn (neurotransmitter)
helps excite the muscle (to contract) and sodium ion channels to open and Na then flows into muscle (excites muscle causing Ca to leave)
Duchenne Muscular Dystrophy
genetic, incurable myopathy
Cause: genetic error in dystrophin protein (holds muscle fibers together during contraction) gene
common in boys
S&S: muscle weakness
death usually by respiratory or cardiac failure
Diagnosis: physical examination, evaluation of gait abnormailty, and pseudo hypertrophy of calves
Treatment: none, symptoms management
mitochondrial myopathy
Cause: defect in ATP production in mitochondria
S&S: progressive muscle weakness, hearing loss, diabetes, heart problems, nervous system disorders
Diagnostic tests: genetic tests, biochemical tests, EMG, muscle biopsy
Treatment: none (some drugs increase symptoms)
myasthenia gravis
Cause: immune system attacks acetylcholine receptors at neuromuscular junction
S&S: progressive muscle weakness
Diagnostic Tests: blood tests, EMG
Treatment: steroids, immunosuppresent drugs, plasma exchange, acetylcholine esterase inhibitors
Tetanus
Cause: bacterial infection, clostridium tetani
S&S: progressive descending muscle spasm, paralysis, stiffness and pain
Diagnostic tests: physical exam, lab tests, history of wound
Treatment: wound hygiene, tetanus antitoxin, sedation, ventilator support, pain management