Unit 2 Muscle Flashcards
skeletal muscle embryonic origins
mesoderm
somites
cardiac muscle embryonic origins
splanchnic mesoderm
smooth muscle embryonic origins
somatic mesoderm
splanchnic mesoderm
types of muscle tissue
skeletal
cardiac
smooth
muscle fibers
elongated
only skeletal and smooth
skeletal muscle
attach to bones or skin
single, very long, cylindrical, multinucleate with striations
voluntary
contract rapidly, tire easily, powerful
skeletal muscle tissue
packaged into skeletal muscles; organs that are attached to bones and skin
skeletal muscle fibers
longest of all muscle and have striations
terminology
muscle fiber = muscle cell
syncytium = multinucleate
sarco = meat
epimysium
dense irregular CT surrounding entire muscle; may blend with fascia
perimysium
fibrous CT surrounding fascicles
endomysium
fine areolar CT surrounding each muscle fiber
muscle fiber
sarcolemma sarcoplasm myofibrils sarcoplasmic reticulum T tubules
sarcolemma
muscle fiber plasma membrane
sarcoplasm
muscle fiber cytoplasm
contains many glycosides for glycogen storage, myoglobin for O2 storage
myofibrils
densely packed rodlike elements
accounts for approx. 80% muscle fiber volume
myofibril features
striations
sarcomeres
myofilaments
striations
stripes formed from repeating series of dark and light bands along length of each myofibril
A band
dark regions
H zone
M line
thick and thin filament
H zone
lighter region in middle of dark A band
thick filaments
sarcoplasmic reticulum
- network of smooth ER tubules surrounding each myofibril
- run longitudinally
- terminal cisterns from perpendicular cross channels at A-I band junction
- regulation of intracellular calcium levels
M line
line of myomesin (protein) that bisects H zone vertically
I bands
lighter regions
Z line (disc)
thin filament
Z line
coin-shaped sheet of proteins on midline of light I band
sarcomere
smallest contractile unit
A band with 1/2 I band at each end (Z line-Z line)
M line bisects H band
myomesin anchors adjacent thick filaments
sliding filament model
thin actin filament reversibly and slide over thick myosin filament
requires ATP expenditure, presence of calcium
muscle contraction
- total length of sarcomere decreases
- Z discs move closer together
- I band length decreases
- A band length doesn’t change
myofilaments
orderly arrangement of actin and myosin within sarcomere
actin myofilaments
thin, extend across I bad, partway to A band
anchored by Z line
myosin myofilaments
thick, extend length of A band
connected at M line
T tubules
- tube formed by profusion of sarcolemma deep into cell interior at A-I band junction between terminal cisterns
- allow electrical nerve transmissions to reach deep into interior of each muscle fiber
triad
skeletal
area formed from terminal cistern of one sarcomere, T tubule, and terminal cistern of neighboring sarcomere
T tubules (alt. def.)
- deep invagination of the sarcolemma (skeletal/cardiac)
2. allow depolarization of membrane to quickly penetrate to the interior of the cell
repair of skeletal muscle
fibers are most-mitotic
finite satellite cells can be exhausted
satellite cells
skeletal
within basal lamina
myogenesis
divide to produce myoblasts to fuse and replace fibers
cardiac muscle
striated, involuntary
forms myocardium
branched with 1-2 nuclei
cells joined by intercalated discs
diad
cardiac
T tubules
single cisterna of SR
located at Z lines, one per sarcomere
intercalated discs
desmosomes
gap junctions
cardiac SR
less elaborate than skeletal
single terminal cisterna
diads
cardiac T tubules
wider, less numerous
one per sarcomere
cardiac muscle repair
post mitotic
cells are replaced with non-contractile CT
smooth (visceral) muscle
non striated, involuntary
small tapered cells with centrally located nuclei
SR is reduced/absent
no sarcomeres
bundles of crisscrossing myofilaments
form bundles, sheets linked via gap junctions
fusiform
smooth muscle repair
mitotic
replace lost cells or increase mass
hyperplasia
increase number
hypertrophy
increase size
smooth muscle specializations
caveolae
dense bodies
caveolae
invagination of smooth muscle cells
ion channels
associated with SR
dense bodies
act like Z disc
