what does the SR store - proteins and calcium
what is the role of the transverse tubules in the muscle fiber - allow inside of muscle to communicate
... [Show More] with the outside of the muscle
how is a sarcomere measured - from z-disc to z-disc
what is contained in the I band of the sarcomere & what color is the band - thin filaments
titin
z-disc
light (isotropic)
what is contained in the A band of the sarcomere & what color is the band - thick filaments
thin filaments
dark (scatters light)
what is contained in the H zone & what color is the band - thick filaments
light
no barbs or myosin
middle zone of the sarcomere
what is contained in the M line - in the middle of the sarcomere, middle of H zone
thick filaments
myomesin
what does titin do in the sarcomere - structural protein
how many zones can you see when the sarcomere is relaxed - all zones can be seen in relaxed state
how many zones can be seen when the sarcomere is contracted - sarcomere shortens
I band shortens
H zone disappears
thick and thin filaments overlap DONT shorten
what is the contractile unit of skeletal muscle - the sarcomere
what is the main component of the thick filaments - myosin
have heavy and light chains
motor heads that move it along the thin filament
what is the largest protein in the body - titin
what are the main components of the thin filaments - actin (where myosin binds)
troponin (moves tropomyosin when Ca2+ is present)
tropomyosin (covers actin active site)
nebulin (sets thin filament length)
CapZ (anchors actin to Z-line on z-disc side)
Tropomodulin (on end of actin, in middle of sarcomere)
alpha-actinin (anchors actin to z-line)
what does desmin do in the sarcomere - interacts with alpha-actinin to anchor z-disc to sarcolemma
what does dystrophin do in the sarcomere - connects sarcomere to sarcolemma
stabilizes the sarcolemma to prevent damage during contractions
1st step of cross-bridge cycle - BINDING
activated myosin binds to actin
ADP and Pi are still bound to myosin
2nd step of cross bridge cycle - POWER STROKE
myosin head swivels
movement of actin filament
ADP and Pi released from myosin
(Pi is released first, before ADP is released)
3rd step of cross bridge cycle - DISSOSCIATION
ATP binds to myosin
Actin and myosin dissociate (cross bridge detaches)
4th step of cross bridge cycle - ACTIVATION
ATP hydrolysis energy activates myosin head
ADP and Pi remain bound to myosin
if Ca2+ still present, cycle continues
how does Ca2+ effect the cross bridge cycle - Ca2+ is needed for the troponin to move the tropomyosin off the actin
when Ca2+ runs out, the cross bridge cycle will stop
troponin has 4 Ca2+ binding sites [Show Less]