myosin heads contain 2 smaller, ______ _____________ _______ that act as cross bridges during contraction.
ATP binds to the myosin _____.
TRUE or FALSE: actin has no head or tail.
__ actin bears active sites for myosin head attachment during contraction.
__ actin consists of G actin subunits. Also called fibrous actin.
TRUE or FALSE: troponin is bound to tropomyosin not to actin.
TRUE or FALSE: the SR is in contact with every myofibril so it is present when the muscle needs to contract.
what takes the action potential from the nerve to the cell?
t tubule proteins are _______ sensors.
SR foot proteins are gated channels that regulate ______ release from the SR cisternae.
TRUE or FALSE: just because there is contraction that does not mean there is shortening.
skeletal muscles are stimulated by ________ motor neurons.
axon terminal and muscle fiber are separated by a gel-filled space called the ________ _____.
TRUE or FALSE: in the generation of an action potential Na+ moves into the cell until it reaches the threshold. At that point the muscle contracts. It is all or none--like firing a gun. It only takes 1 force.
in ___________ Na+ channels close and voltage-gated K+ channels open.
TRUE or FALSE: during repolarization that muscle cannot contract.
what is the threshold number of muscle?
what is the resting number of muscle?
the ______ period is the time between AP initiation and the beginning of contraction.
it changes shape
what does voltage-sensitive tubule protein mean?
Ca2+ and ATP
What 2 things are required for cross bridge cycling?