Histology - UCI Medicine - Muscle
Terms
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- muscle cells: char
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multinucleate (peripheral nuclei)
from a single myoblast
polygonal shape in x-section
one cell can be as long as whole muscle - damage to muscle fiber
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will die
myoblasts still present and will regenerate missing fibers - skeletal muscle in tongue: char
- multidirectional fasciculi
- perimysium
- separates fasicles
- sarcomere bands
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Z: disc (thin line): connections of actin (alpha actinin binds it to z disc)
A: dark: thick myosin fibers and overlap of actin
I: light: actin only - myosin components
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heavy and light meromyosin chains:
two alpha helices of rod light make up light
heavy is just the end, includes some light parts and the heavy heads - light meromyosin
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won't complex with actin
will form filaments - heavy meromyosin
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ATPase activity
won't form filaments - sliding filament theory of contraction
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ADP form of light chain has affinity for thick filament
power stroke: when no ADP is present
with just ADP will cause state of rigor (mortis): cross linking betw. actin and myosin filaments - calcium dependent reg. of contraction
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tropomyosin: chain that holds troponin
troponin: no Ca2+ will hold actin filament awy from actin head
w/ Ca will expose binding site for contraction - t-tubules and sarc. reticulum
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SR encloses myofibril
t-tubule triad (system) links SRs together
t-t is depaolarized and Ca channels open up to fill cytoplasm around myofibril->contraction->free Ca recovered to shut down contraction - triad
- a t-tubule and the ends of two adjacent SRs makes up the t-t triad
- type 1
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-slow twitch
-resistant to fatigue
-lots of myoglobin
-smaller diameter->gen. less force
-contract slowly
-aerobic resp. dep.<-^mitochon.
-have smaller nerve fibers - type II
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fast twitch
-low myoglobin->white muscle
-larger diam.
-rapid contraction
-anaerobic, glycolysis, few mito., fatigue quickly
-inn. by large diam. nerve fibers - muscle fiber typing (I or II)
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number of mitochondria (TCA assay)
slow: stain darkly b/c of more mito.
fast: stain lighter
denervation renervation will cause you to lose checkerboard pattern of fast/slow-> prblem - Duchenne Musc. Dystrophy
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prob in dystrophin (just beneath membrane)
linking actin cytoskeleton to EC matrix
histology:
round or swollen m. fibers
macrophages present
central nuclei (newly formed cells) - muscle spindles
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sensory structures in muscle fibers
prioprioceptors
relays info about muscle movement - golgi in muscle
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sensory organs in tendons
tell about stretch - cardiac muscle: char
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centrally placed single nucleus
bifurcated
intercalated discs connecting cells - cardiac muscle: histology
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variability in diameter (because of branching)
central nucleus obvious in cross section
striations seen in EM - intercalated discs
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complex of cell/cel connections
fascia adherens: like zonula adherens
desmosome: spot welds
gap jxns: electrical/metab. conxtn - intercalated disc: histology
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darks spot is desmosome
actin filament is adhered to adherens
where memb. is very close, where gap jxns are - atrial granules
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only in atrial walls
endocrine
contain peptide to reg. BP
^BP->^vasodilation - purkinje fibers: char
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conducting cells that keep heart beating in rythm
signal begins at SA node and propagates out to AV node->purkinje cells
make up AV node and bundle of His, etc. - purkinje fibers: histo
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large diam fibers with few contractile fibers
stain lightly, look empty - smooth muscle: char
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large ducts, uterus
spindle shaped
orthogonal fasicles: multidirectional
actin and myosin throughout cytoplasm, no bands - smooth muscle: histo: EM
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-oval shaped nucleus
-round in cross section
-perimysium between fasicles
-actin and myosin random in cytoplasm
-desmosome jxn also where actin attached
-gap jxns for e- coupling