Contraction of Skeletal Muscle fasicle A Muscle Fiber 1 sarcolemma muscle cell membrane extends into muscle fiber forms Ttubules 2 sarcoplasmic reticulum ID: 342049
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Slide1
7.2 Microscopic Anatomy and Contraction of Skeletal Muscle
(fasicle)Slide2
A. Muscle FiberSlide3
1.
sarcolemma
* muscle cell membrane
* extends into muscle fiber (forms T-tubules) Slide4
2.
sarcoplasmic reticulum
(SR)
* has calcium (Ca
2+) storage sites Slide5Slide6
3. Myofibrils and SarcomeresSlide7
a.
myofibrils
* threadlike strands within muscle fibers
* composed of 2 types of
myofilaments : Slide8
thick filaments
* composed of protein
myosin
(shaped like a golf club
- head/tail)Slide9Slide10Slide11
thin filaments
* 2 twisted strands of protein
actin
(contains myosin binding site)Slide12Slide13
* other proteins:
tropomyosin
–
long (wraps around
actin
)
covers the myosin binding sitesSlide14
troponin
–
smaller (bound to
tropomyosin
)
has calcium binding sites.Slide15
b.
sarcomeres * contractile sections of myofibril (striations)
* extend between 2 dark lines (
Z lines
)
Slide16Slide17Slide18Slide19
The Sarcomere
A band
I band
Z disc
sarcomere
thick filament (myosin)
thin filament (actin)
M line
H zoneSlide20
“Sliding Filament” Mechanism
Contraction results from the sliding action of actin and myosin filaments
RELAXED:
CONTRACTED:Slide21
c. Sliding Filaments
* sarcomere shortens = contraction
* thin filaments slide past thick filaments:Slide22
“sliding filament theory”Slide23Slide24Slide25Slide26Slide27Slide28Slide29Slide30
muscle (epimysium)
fascicle (perimysium)
muscle fiber
(endomysium)
myofibril (sarcomeres)
myofilaments (thick & thin)