muscles Flashcards
what is the smallest unit of the muscle
myofibril
what is a myofibril made up of
sarcomeres
what are myofibrils surrounded by and what to they contain
sarcolema
what are the two main protein that make up the sarcomere
actin and myosin
describe the structure of actin
fibrous, two strands twisted around each other
describe the structure of myosin
myosin head and myosin tail
which part of the sarcomere does the myosin form
the thick filament
which part of the sarcomere does the actin form
the thin filament
what is the I band
just actin (at the ends)
what is the A band
everywhere that theres myosin (overlapping and on its own)
which band is darker A or I
A
what is the H zone
just myosin (the very centre)
whats the Z line
the middle line (splits the I band in two)
what protein does calcium bind to and Tropomyosin is bound to
Troponin
Sliding Filament Mechanism
Acetylcholine binds to receptors on the muscle and causes a wave of depolarisation. And this travels down the T tubule and causes calcium ion gated channels to open on sarcoplasmic reticulum and calcium leaves the sarcoplasmic reticulum and goes into the sarcoplasm. This causes Tropomyosin to move, meaning the myosin binding site is now free. Myosin head binds to the actin. It has ADP and Pi bound. The myosin head bends forwards. This causes the ADP and Pi to be released. ATP binds which causes the myosin head to detach from the actin. Then ATP hydrolysis bends it back to its original position and it starts again.
