Tropmyosin and Troponin are called the regulatory proteins in muscle contraction. Describe the myofibril organization and specific structural and functional role of these two proteins in muscle contraction-relaxation cycle.

3.4. About human skeletal muscle contraction, what are the correct statements? PHYSIOLOGY_basic (OJO) A muscle fiber is made by the parallel apposition of sarcomers. Generation of force relies on the formation of cross-bridges between actin and myosin filaments. In the process of contraction, adenosine triphosphate (ATP) is required both to drive the actin-myosin association-dissociation cycle and to recycle calcium back to the endoplasmic reticulum. Each muscle fiber is innervated by one neuron only. T tubules are plasma membrane invaginations of the sarcolemma that allow excitation-contraction coupling.

The release of calcium ions initiates muscle contractions.Watch this video (http://openstaxcollege.org/l/calciumrole) to learn more about the role of calcium. (a)What are “T-tubules” and what is their role? (b) Pleasealso describe how actin-binding sites are made available forcross-bridging with myosin heads during contraction.

What is the most outer covering (made up of areolar connective tissue sheath) of a muscle fiber called?     endomysium     perimysium     epimysium     sarcolemma What do synaptic vesicles of a neuromuscular junction contain?     sodium     serotonin     calcium     acetylcholine