Lecture 9/10 Flashcards
muscle
shape and characteristics of muscle cells
Elongated cells containing a
great number of cytoplasmic filaments
origin of muscle cells
Mesodermal. Differentiation occurs mainly by a
process of cell lengthening and synthesis of myofibrillar
proteins
different types of muscle and general differentiations.
- Skeletal striated muscle presents cross striations, is voluntary and is attached by
connective tissue to bones - Smooth muscle does not have cross striations and is involuntary
- Cardiac muscle is striated and involuntary
most abundant type of muscle
skeletal muscle
how are muscle cells attached to CT?
attached to collagen by junctional complexes associated with infolding of the plasma membrane (sarcolemma) of the muscle fibre
what are 3 coats of CT that organize the muscle?
classify each
- Epimysium is the dense connective tissue that surrounds the entire muscle.
- Perimysium is the connective tissue that surrounds each bundle of fibres or fascicles.
- Endomysium is the thin layer of connective tissue surrounding each muscle fibre
what fibers and structures are found in the endomysium?
- reticular fibrils (collagen type III)
- elastic fibres
- capillaries
how are muscle fibers made?
multinucleated and results from the embryonic fusion of uninucleated myoblasts
what is the sarcolemma?
cell membrane, or unit membrane
what is the sarcoplasm?
the cytoplasm
where are the nuclei located in skeletal muscle?
peripherally, just under the sarcolemma
what are satellite cells?
stem cells that sit between the
basal lamina and the sarcolemma
what are the main organelles in muscle fibrils?
- myofibrils
- mitochondria
- sER
when does hypertrophy occur in muscle?
in striated muscle (normal in skeletal and abnormal in cardiac)
when does hyperplasia occur in muscle?
normal in smooth muscle
role of CT in skeletal muscle?
mechanical tranducer to
the forces generated by the
contracting muscle cells.
fascicle
bundle of muscle fibers
what are the different lines and bands in the sarcomere?
- Z-line
- I-band
- A-band
- H-band
- m-line
what is the sacromere?
smallest repetitive subunit of the contractile apparatus. The
sarcomere extends from Z line to Z line
what makes up thick filaments?
myosin (2 heavy chains and 4 light chains)
what is present in the M-line?
creatine kinase, which makes ATP from phosphocreatine
role of satellite cells?
make skeletal muscle have limited regeneration since can “give” one of their nuclei to the muscle fiber
what does chymotrypsin do?
cleave the myosin into light meromyosin (LMM) and heavy MM (HMM)
what does papin do?
cleave the HMM into HMMS-1 and 2
what is HMMS-1?
an ATPase and actin binding site
what makes up the thin filaments?
actin
what are the troponin subunits and their roles?
- Tnl: inhibit the actin-myosin interaction
- TnC: binds Ca2+, allowing binding of myosin and therefore cause movement
- TnT: anchors to tropomyosin
where is titin found and what is its role?
in sarcomere, in the I-band where there isn’t any thick filaments, found in between the thin filaments and provides stability by anchoring the thick filaments with the z-disc
where is calcium ATPase and calsequestrin found?
in a terminal cisterna (at an A to I band junction)
Myelinated motor nerves branch out within the ____________ where each nerve gives rise to several terminal wigs called ____________.
perimysium and endomysium; terminal boutons.
what makes up the intercalated disk?
and what are the component of each seperate part?
- zonula adherens: α-Actinin/Vinculin/cadherens
- macula adherens (desmosome): Desmocollin/Desmoglein and Desmoplakins I and II, Plakoglobin, Desmocalmin
- gap junction (the lateral part): connexin 48 (predominantly)
what fibers/filaments are present in smooth muscle and how are they organized?
on dense bodies, where actin filaments branch out. then, myosin filaments are scattered on the actin.
reticular fibers are found outside the BM
