Motor Units
What is a "Motor Unit"
One motor neuron plus all of the muscle fibers that it stimulates.
Many muscle fibers make up a...
Fascicle
Tropomyosin
What type of neurotransmitter is released to stimulate muscle contraction?
Acetylcholine (ACh)
Which is the thin filament?
Many fascicles make up a...
Muscle
What is a "cross bridge"
When myosin heads bind to actin filaments.
What is the function of calcium binding to troponin?
Alters shape of troponin and moves tropomyosin off myosin binding site on actin
What does calcium bind to in the muscle cell?
Troponin
What is blocking myosin from binding to actin when a muscle is relaxed?
Tropomyosin
Many myofibrils make up a...
What is the event called when myosin crossbridges pull actin towards the center of the sarcomere?
Power stroke
What happens when when acetylcholine is released?
It stimulates the release of calcium from the sarcoplasmic reticulum.
Which filament moves during a contraction?
Actin
What structure releases calcium?
Sarcoplasmic Reticulum
What controls the movement of tropomyosin?
Troponin, regulated by calcium.
What part of the sarcomere contains ONLY actin?
I band
Large motor units -> powerful, non-specific movements
Small motor units -> small, specific movements
Motor neuron releases acetylcholine -> acetylcholine causes the release of calcium from the sarcoplasmic reticulum -> calcium binds to troponin -> troponin moves tropomyosin off of the myosin binding sites -> myosin binds to actin -> muscle contracts
What surrounds the muscle as a whole?
Epimysium
What is the last step of the cross bridge cycle?
ATP binds to the myosin head causing the myosin to release from the actin and reset for another power stroke.
Which areas of the sarcomere essentially disappear when a muscle contracts?
The I band and the H zone.