Muscles II: Microscopic Anatomy/Sarcomere Flashcards
(48 cards)
components of muscle fiber
sarcolemma, sarcoplasm, sarcoplasmic reticulum
two main structures unique to muscle fibers
t-tubules, sarcoplasmic reticulum
t-tubules
deep invaginations of the sarcolemma that extend into the sarcoplasm
t-tubules purpose
carry impulses from sarcolemma to help stimulate contraction. bring sarcolemma close to sarcoplasmic reticulum and all regions of the cell
where do t-tubules open to?
the outside of the muscle fiber
do t-tubules contain extracellular fluid?
yes
sarcoplasmic reticulum
internal membrane complex
purpose of sarcoplasmic reticulum
stores calcium used to initiate contraction
cisternae of sarcoplasmic reticulum
enlargend portion of calcium storage that released calcium when action potential travels down the transverse tubules eliciting muscle contraction
triad
structure made up of two terminal cristae and one t-tubule
purpose of triad
link between sarcolemma and sacroplasmic reticulum at all regions to have synchronous release of calcium (allows muscles to contract forcefully)
myofibrils
cylindrical structure within the muscle fibers that run the length of the cell
myofilaments
strands of protein that allow for contraction
2 types of myofilaments
thin, thick filaments
thick filaments are composed of
myosin
myosin 2 strands
intertwined tails and globular head
what do heads of the myosin form?
cross bridges
myosin contain binding site for
actin, ATP binding
thin filaments extend toward ____ of thick filament, heads extend ______ toward thin filament
middle, outward
thin filaments composed of
2 f-actin twisted around each other (filamentous)
g-actin shape
spherical
each actin strand is made of
g-actin (globular)
2 regulatory proteins that are part of the thin filament
tropomyosin, troponin
tropomyosin
threadlike protein covering part of actin
