skeletal muscle contraction (midterm 1) - look at figures as well Flashcards
what are satellite cells
resident progenitor cells which matures into either another satellite cell or a myoblast
what is a myoblast
mononucleated cells that fuse to form myotubes
what are myotubes (myofibrils)
multinucleated, function cell of skeletal muscle
what are myofibers
organized structures of myotubes
what happens to satellite cells during skeletal muscle regeneration
they become activated and proliferate -> they can repopulate the reserve or differentiate into myoblasts (absolute number of satellite cells decreases with age)
in the muscle, how are myofibers organized
they’re stacked and bound by connective tissues that contain nerves and blood vessels
what are skeletal muscles composed of
muscle cells, connective tissue, blood vessels, and nerve fibers
what are the primary functions of skeletal muscle
contraction, force generation, and induction of movement
what is the parenchymal cell
muscle fiber responsible for muscle contraction
what is muscle fiber composed of
(10-80 um diameter) sarcolemma -> membrane: muscle -> tendon -> bone
what are myofibrils composed of
sarcomere: actin and myosin
what is an A-band
anisotropic (polarized light) => dark -> areas with both myosin and actin
what is an I-band
isotropic => light -> areas with just actin that helps identify a z-disk
what does a skeletal muscle look like
PICTURE IN NOTES PG 5
what is the sarcolemma
cell membrane of the muscle fiber
what are the ends of actin filaments attached to
a Z disc, which interdigitates with the myosin filaments
what is a sarcomere
the portion of the myofibril that lies between two successive z discs -> normally 2 um when fully stretched resting length
what is titin
maintains the side-by-side relationship between the myosin and actin filaments
what is sarcoplasm
intracellular fluid the spaces between the myofibrils are filled with
what is myosin molecules composed of
two heavy chains (make up myosin tail) and four light chains (make up myosin head)
what are actin filaments composed of
actin, tropomyosin, and troponin
- composed of polymerized G-actin molecules, which each contain one ADP
what are ASP molecules thought to be
active sites on which the cross-bridges of myosin filaments interact to cause muscle contraction
what does it mean when z-bands are closer
more actin and myosin connection = more FORCE
what are the three loosely bound protein subunits of troponin
troponin I = strong affinity for actin
troponin T = strong affinity for tropomyosin
troponin C = strong affinity for calcium ions
what is the walk-along theory of contraction
after Ca++ activation, the heads of the cross-bridges from the myosin filaments become attracted to the active sites of the actin filament, and causes contraction to occur
what is the energy source for contraction
ATP
what determines tension in muscles
actin overlap - more overlap = more tension
how long are sarcomeres
2.2 um - know the figures on slide 24 and 25
what occurs with more fast fibers
faster muscles
what provides 5-8 seconds of additional contraction
phosphocreatine
what provides 60 seconds of contraction
glycogen
what occurs with isometric contraction
muscle length does not change during contraction
what occurs with isotonic contraction
muscle tension does not change during contraction
