Skeletal Muscle Flashcards
What are the 3 types of muscle
Skeletal, Smooth, and Cardiac
Where are the nuclei of skeletal muscle located
On the periphery
Skeletal muscle have a _______ arrangement
Sarcomeric
Skeletal muscle has a ________ syncytium
Multinucleated
Each skeletal muscle fiber is innervated via
a single motor neuron
Contraction of skeletal muscle is
all or none
Skeletal muscle contains what troponin
C
Skeletal muscle cells (fibers) are formed during embryonic development when ?
Hundreds of individual mononucleated myoblasts join end-to-end to form a myotube
The myotube matures into the what
cylindrical myocyte with hundreds of nuclei
Each myocyte is about ___ to ___ in diameter
50 to 60 micrometers
Type I skeletal muscle fibers have intense staining for what
oxidative enzymes
Type I myofibers are rich in what 3 components
NADH transferase, myoglobin, ATPase
Type I myofiber types possess many ?
Mitochondria
Type I myofbers primarily utilize what for energy
oxidative phosphorylation
Type I myofibers produce ___ and ____ contractions
Slow and continuous
Type I myofbers are referred to as _____ or ____ fibers
dark or red
Type IIA myofibers are _________staining for oxidative enzymes
intermediate
Type IIA myofibers utilize both _____ and _____ respiration for ATP production
Aerobic and anaerobic
Type IIA contract more rapidly than what type of fibers
Type I
Type IIA are ____ to fatigue
resistant to fatigue
Type IIB are _____ staining for oxidative enzymes
Light staining
Type IIB utilize primarily _____ for ATP production
Anaerobic respiration
Type IIB contract ________ than type I or Type IIA
more rapidly
Type IIB fatigue ______?
quickly
Type IIB are referred to as ___ or ___ fibers
white or light
Smooth muscle cells are _____ nucleation
mononucleated
Do smooth muscle cells have sarcomeric arrangement
No
Smooth muscles are innervated via
The ANS
Do smooth muscle cells respond “all or none”
No
Smooth muscle cells are connected via?
Gap junctions
Cardiac muscles cells show what kind of nucleation
mononucleated
What is the position of the nuclei in cardiac muscle cells
centrally positioned
In cardiac muscle cells often what
Branch
Cardiac muscle cells have a _____ arrangment
Sarcomeric
Cardiac Muscle cells communicate via
Gap junction: intercalated discs
Are cardiac muscle cells directly innervated
No
Muscle is composed of many?
Fasicles
A fascicle is a bundle of
Myofibers
A myofiber is a bundle of
myofibrils
A myofibril is a
linear array of sarcomeres
Sarcomeres are made up of what two kinds of filaments
Actin (thin) and myosin (thick)
Muscle is covered by a CT sheet called the what
epimysium
A fascicle is surrounded by a CT sheet called the what
perimysium
The perimysium consists of what
fibroblasts and Type I collagen fibers
A myofiber is a muscle cell and is surrounded by a
cell membrane
The cell membrane of a muscle cell is called the
sarcolemma
what covers the muscle fiber, including the sarcolemma
endomysium
The endomysium consists of what
basal lamina and reticular collagen fibers
The basal lamina is secreted by
muscle cells
What is the function of the basal lamina
anchors muscle fibers to each otherhelps to distribute the force of contraction
Sarcomeres are separated from each other by what
z disks
The sarcomere shortens during a contraction as evidenced by what
the z disks becoming closer together
Myosin is a ____ protein with long tails and ___ heads at one end
dimeric, two
Each of the myosin heads has what three characteristics
Actin binding region, ATP-binding region, Light-chain binding region
What are the two kinds of light chains
essential and regulatory
The light chains are similar to ____ but have lost the ability to bind what
calmodulin, calcium
Function of essential light chains
thought to control binding of myosin heads
Function of regulatory light chains
maintain the stability of Myosin II, sites for phosphate binding
what is the name of a polymer of G actin
F actin
F actin’s plus end inserts on the
Z-disk
F-actin’s minus end faces the
H band
Each f actin filament consists of
two polymers wound in an alpha-helix configuration
name two actin associated molecules in skeletal muscle
Troponin and Tropomyosin
Tropomyosin sits where
in the groove between two actin strands of an actin filament
Each tropomyosin spans how many actin monomers
7
Troponin is a complex of what three moelcules
Troponin I, Troponin C, Troponin T
What is the function of Troponin I
Inhibits binding between actin and myosin
What is the function of Troponin C
Binds calcium ions
What is the function of Troponin T
Binds to tropomyosin
____ is the a muscle cells equivalent to endoplasmic reticulum
Sarcoplasmic reticulum
Enlargements of the sarcoplasmic reticulum are located next to what
T-Tubules
Enlargements of the sarcoplasmic reticulum are refferred to as what
Cisternae
Cisternae sequester what
Calcium ions
T-Tubules are what
extensions of the sarcolemma that extend down into the sarcoplasm
Where are T-Tubules of skeletal muscle located
Where the A and I bands meet
T-Tubules provide _______ for myofiber contraction by transferring the AP of the sarcolemma into _____ release from the cisternae
electromechanical coupling, calcium
Each _____ molecule extends from the z-band along the length of one thin actin filament
Nebulin
_____ acts like a template for the regulation of thin filaments length
Nebulin
Each titin molecule extends from
Z-disk to M-line
During relaxation titin generates ______ through ____ when the sarcomere is stretched
Passive tension, elastic extension
A segment of _____ is closely associated with myosin and maintains the central position of the thick filaments in the sarcomere
Titin
Alpha beta- crystallin is what
heat-shock protein that protects desmin from mechanical stress
What is dystrophin
one of the proteins that links the alpha-actinin/desmin complex to cytoplasmic side of sarcolemma Anchors actin to the sarcolemmaReinforces sarcolemma during muscle contraction
What links dystrophin (intracellular) to laminin-2 (extracellular)
Dystroglycan complex
What attaches thin filaments to the z-line
alpha actinin
What are the two main function of titin
Provides myosin with elasticitycenters thick filaments in the sarcomere
What extends form z-disk to middle of H-band and connects ends of thick filaments to Z-line
Titin
Titin has a molecular weight of about
3 million
What binds desmin filaments
Plectin
What is the framework of desmin filaments which surrounds the Z line and extends into each sarcomere
Desmin intermediate filaments
What links myofibrils laterally and to the sarcolemma
Desmin intermediate filaments
What extends form z disc to end of actin filaments
nebulin
What serves as the template to regulate length of actin filaments
Nebulin
What links actin filaments to transmemebrane proteins of muscle cell plasma membranes
Dystrophin
Dystrophin is a ______
Calponin
Dystrophin, a calponin, links actin filaments ot transmembrane proteins of muscle cell plasma membranes, which then link to the ECM, for what purpose
help maintain cell stability during muscle contraction
Muscular dystrophy, is inherited how
X-linked
Muscular dystrophy results in what
progressive degeneration of skeletal muscle
Dystrophin is absent in patients with what
Duchenne’s muscular dystrophy
Dystrophin is abnormal in patients with what
Becker’s muscular dystrophy
An intermediate filament extending from one myofibril to the other and anchored to the sarcolemma, encircles the Z disk of each sarcomere
Desmin
Desmin inserts into specialized sarcolemma attachment regions known as what
costameres
Desmin facilitates the what
coordinated contraction of individual myofibrils by holding adjacent myofibrils together and linking them to the sarcolemma
What links adjacent design filaments to each other
Plectin
what is a heat shock protein associated with design, that protects this intermediate filament form street-induced damage
alpha beta- Crystallin
Mutations of ____, ___, and _____, cause fragility of the myofibrils and their destruction after continuous stress
Desmin, plectin, alpha beta- crystallin
Mutation in _____ causes congenital muscle dystrophy
Laminin 2
what links dystrophin to laminin-2
Dystroglycan complex
Satellite cells attache to _____ before ____ is laid down
Myotubes, basal lamina
Satellite cells function as
Stem cells
Are Satellite Cells generally quiescent
Yes
Satellite cells can become ______ in times of stress
mitotic
Satellite cells give rise to
myogenic precursor cells
What is the function of myogenic precursor cells
replace damaged muscle by proliferating, fusing, and differentiating into skeletal muscle fibers.
Satellite Cells have a ____ receptor that when acted on by ___ makes them proliferate
C-Met Recepotr, HGF
What are the components of the neuromuscular spindle
Extrafusal fibers Intrafusal fibers Alphamotor neurons Gamma motor neurons Primary and secondary afferent fibers
What are the two kinds of intrafusal fibers
Nuclear bag fibers and Nuclear chain fibers
The Nuclear bag region is the ____ region
Sensory region
The alpha motor neurons extend to the ____ fibers
extrafusal fibers
The gamma motor fibers extend to the
intrafusal fibers.
The intrafusal fibers are _____ than the extrafusal muscle fibers
thinner
Contraction of ____ muscle fibers, arranged in parallel to the spindle, reduces tension on the muscle spindle, which slacks
extrafusal
Activation of gamma motor neurons of the spindle does what
contracts the poles of the spindle thereby pulling the sensory region supplied by sensory nerve fibers.