Which of the following is the last step in the muscle stroke cycle?
a. calcium ions bind to the protein troponin
b. myosin heads form cross-bridges with actin filaments
c. depolarization of the t tubules
d. displacement of tropomyosin, exposing myosin-binding sites on actin
e. atp hydrolysis, the myosin head unbinds the cross-bridge

E. ATP hydrolysis, the myosin head unbinds the cross-bridge

Explanation:

Muscle contraction can be explained by the sliding filament theory and the sequence of events are as follows:

a) Release of acetylcholine neurotransmitter from the motor neuron innervating the muscle fiber at neuro-muscular junction.

b) The membrane of the fiber depolarizes as sodium ions enter inside and an action potential is generated. This action potential propagates to the T- tubules as well.  

c) Depolarization of T-tubules triggers the release of calcium ions from the sarcoplasmic reticulum.

d) Calcium ions bind to TpC component of troponin which causes conformation change and displaces the tropomyosin-troponin complex from myosin binding sites on the surface of actin.

e) Myosin heads can now bind to actin filaments and form the cross-bridges.

f) The actin filaments are then pulled by the myosin heads towards the sarcomere.  This is called the power stroke.

g) Myosin head also has an ATP binding site. Once ATP binds the myosin head detaches from actin.

From the above points, the order of events in the given question would be: C-A-D-B-E

answer: i feel like it would be 3

explanation:

what about it?

is this a ?