Skeletal Muscle Flashcards
myopathy
disorder of muscle
segmental muscle necrosis
destruction of a portion of the myocyte length
how does muscle regeneration occur
satellite cells reconstitute destroyed muscles
when does fiber hypertrophy occur
response to an increase in load
myotonia
tonic spasm of one or more muscles
hypotonia
deficient tone or tension
arthrogryposis
fixation joints in an extended or flexed position
what is creatine phosphokinase (CK; CPK)
enzyme highly concentrated in muscle and brain
Gower’s sign
indicates weakness of the proximal muscles
- uses hands and arms to walk up form squatting position
Myofibril
repeating units of sarcomeres
What defines a sarcomere
Z line to Z line
what makes a thin filaments in the muscle
actin
what makes up thick filaments in the muscle
myosin
what is the Z band primarily made up of
actin
what is the cell membrane of a muscle cell called
sarcolemma
what is the cytoplasm of a muscle cell called
sarcoplasm
when a muscle cell contracts what regions contract, lengthen.
I band shortens
A band unchanged
acronym of muscle fibers
One slow fat red ox
1, lipid rich, high myoglobin, oxidative
which muscle fiber is for sustained use? sudden use?
fiber 1: sustained
fiber 2: sudden
grouped atrophy
loss of a motor neuron leads to atrophy of associated muscle
fiber type grouping
neuron/axon drop out leads to larger motor units
Denervation atrophy is disorder of what? breakdown of what?
- motor neurons
breakdown of myosin and actin
what is wrong in spinal muscular atrophy
progressive destruction of anterior horn cells and cranial nerve motor neurons
another name for spinal muscular atrophy
infantile motor neuron disease
how is spinal muscular atrophy inherited? what gene is messed up
autosomal recessive
-survival motor neuron 1
what happens to the cell in muscular dystrophy
internal nuclei
fibrofatty tissue
what protein is defected in Duchenne MD? what gene?
Dystrophin protein defect from abnormal gene at Xp21 ( deletion > frame shift or point mutation )
what are some clinical features of Duchenne MD?
normal at birth
delayed walking
pseudohypertrophy of calves
increase CK
how do Duchenne MD patients die
respiratory failure, cardiac decompensation, lung infection
compare Becker MD with Duchenne MD
Becker MD less common, less severe, later onset
what part of the body does Limb Gridle MD occur? what does this cause
proximal muscles
- waddling gait because of weak hip and leg muscles
- trouble getting out of chairs or climbing stairs
- reaching over head hard
- holding arms outstretched
Limb Gridle MD is a defect in what
dystrophyn glycoprotein complex
Facioscapulohumeral MD has weakness where in the body? clinical significance
- facial weakness
- wasting of upper arm and shoulder muscles
- scapular bones look like wings when the arms are raised
Emery-Dreifuss MD onset
10-20;
what is the clinical triad for Emery-Dreifuss MD
- early humeroperoneal weakness
- prominent contractures, ( elbows/ankles)
- cardiomyopathy
muscle clinical signifiance for myotonic dystrophy
stiffness, difficulty releasing grip
- precuss thenar eminence
- weak foot dorsiflexion
- weak intrinsic hand/wrist extension
- facial muscle atrophy and ptosis
what are other clinical findings for myotonic dystrophy
cataracts
endocrinopathy
cardiomyopathy
what is wrong in the autosomal dominant myotonic dystrophy? protein and gene?
Dystrophila myotonia-protein kinase (DMPK)
CTG repeat expansion on 19q
what is the anticipation of mytonic dystrophy
onset at a younger age in succeeding generations
what are three types of hypotonic channelopathies
hyp0kalemic
hyperkalmic
normokalemic
what is the most common hypotonic channelopathy, tell me about it
hypokalemic
- Ca channel mutation
- attacks of flacid weakness
MOA of malignant hyperpyrexia
release Ca from SR
- defective Ca channel and RyR1
- ATP depleted by muscle contraction
- anaerobic metabolism
treatment for malignant hyperpyrexia
Dantrolene
clinical presentation for malignant hyperpyrexia
hypermetabolic state with tachypnea and general muscle contraction
central core disease how is inherited
autosomal dominant
what is wrong in central core disease
RyR1 defect
central core disease is a risk for
malignant hyperthermia
what happens in Nemaline Myopathy
- non-progressive hypotonia, weakness
- proximal limb muslces
- subsarcolemmal spindle-shaped particles fromZ band material
what happens to nuclues of centonuclear myopathy
central nuclei usually confined to type 1 fibers
lipid myopathies
accumulate lipid in myocytes
- defects in carnitine transport system
- defect in mitochondrial dehydrogenase enzyme system
mitochondrial myopathies
- defective mtDNA or nuclear DNA
- ragged red fibers from aggregated mitochondira
- parking lot for paracrystalline inlcusions
Dermatomyositis
skin rash precedes or begins with myositis ( grotten lesions and discoloration of eyelids with periobritl edema)
- muscle weakness
Juvenline Dermatomyositis, how is it different from adult
GI involved causing abdominal pain
MOA of dermatomyositis
CD 4 t and b cells
- microvasculature attached by antibodies and compliment creating ischemia
Polymyositis
muscle weakness
- autoantibodies against tRNA synthetases
- cytotoxic CD8 t cells in endomysium destroy muscle
what lymphs are involved for DM, PM , IBM
DM: CD4 and B
PM: CD 8 T
IBM: CD8 T
which inflammatory myopathies respond to immunosupr
DM and PM
site of injury for inflammatory myopathies
DM: capillaries
PM: endomysium myocyte
IBM: endomysium myocyte
where do inflammatory myopathies begin on body
DM and PM: proximal
IBM: distal
intracellular deposits in inclusion body myosistis are similar to what other disease
Alzheimer’s
what happens to the muslces of thyrotoxic mypopathy
acute or chronic proximal muscle weakness
clinicl symptom for thyrotoxic myopathy
exophthalmic ophthalmoplegia
clinical manifestations of hypothroidism myopathy
cramping/aching muscles
slow movements
slow reflexes
proximal weaknes
Ethonal myopathy, what happens after binge drinking
acute rhabdomyolysis
name 3 drugs for drug induced myopathies
steroid ( proximal weakness, type 2 fibers)
chloroquine ( proximal weakness)
statins
what is ICU myopathy related to ? what does this do to muscles
corticosteroid therapy
- degraded myosin thick filaments
MOA for mysthenia gravis
immunemediated loss of acetylcholine receptors
myasthena gravis patients present with
drooping eyelid
diplopia
what is the muscle response for myasthenia gravis
decremental decrease in muscle response to repeated sitmulus
what is the tenselon test
short acting anticholenesterase
Lambert-Eaton myasthenic sydnrome
antibodies inhibit presynaptic calcium channel and block aceylcholine release
Lambert-Eaton myasthenic syndrome most likely comes from what disease
small cell carcinoma in lung
what is the muscle response forLambert-Eaton myasthenic syndrome
enhanced neurotransmission with repeitive stimulation
