Lecture 5: Skeletal muscle contraction Flashcards
Epimysium
Connective tissue surrounding entire muscle
Muscle
Made up of multiple fascicles
Perimysium
Connective tissue surrounding each fascicle
Fascicle
A bundle of myofibers
Endomysium
Delicate connective tissue surrounding each myofiber
Sarcolemma
Cell membrane of muscle fiber
Myofiber
Individual multinucleated muscle cell
Myofibril
A chain of sarcomeres within a myofiber
Myofilament
Actin and myosin filaments that make up a sarcomere
T-tubule
Invagination of sarcolemma that lie close to cisternae of the sarcoplasmic reticulum
Form triads with cisternae
Two per sarcomere
Z-discs (Z-lines)
Anchor actin filaments
Located at each end of sarcomere
I -bands
Composed entirely of actin
Width changes during contraction
A-bands
Composed of Actin and myosin
Width does not change during contraction
H-bands
Composed entirely of Myosin
Width changes during contraction
During contraction, Actin filaments:
Form the I-bands which become narrower in width
During contraction, A-bands:
Are equivalent to the length of the myosin filaments and do not change width
During contraction, H-bands:
Are the part of the A band that is not overlapped by actin filaments and becomes narrower
DHP receptors
Voltage-sensitive calcium channels located on sarcolemma T-tubules
Causes conformation change in ryanodine receptors
Minute amount of calcium flows into cytosol via these channels
Ryanodine receptors
Located on cisternae of sarcoplasmic reticulum
Open in response to DHP conformation change
Allow calcium into cytosol from SR