Answer:
A large vein that carries blood to the heart from other areas of the body. The vena cava has two parts: the superior vena cava and the inferior vena cava. The superior vena cava carries blood from the head, neck, arms, and chest.
The five proteins of the myofilaments are the following:
<span>1.
</span>Myosin, shaped like a golf club, with two
polypeptides intertwined to form a shaftlike tail and a double globular head,
or cross-bridge, projecting from it at an angle.
<span>2. </span>Fibrous actin is like a bead necklace—a string
of subunits called globular (G) actin. Each G actin has an active site that can
bind to the head of a myosin molecule.
<span>3. </span>Tropomyosin. It blocks the active sites of six
or seven G actins and prevents myosin cross-bridges from binding to them when a
muscle fiber is relaxed.
<span>4. </span>Troponin a smaller calcium-binding protein bound
to each tropomyosin molecule.
<span>5. </span>Titin (connectin), run through the core of a
thick filament, emerge from the end of it, and connect it to a structure called
the Z disc.
between 5.6 and 13 cm long
<span>So that the cells can function correctly. </span>
