a. The fiber, as a whole, is surrounded by a membrane known as the sarcolemma. The sarcolemma has specialized invaginations that enter the interior of the fiber at right angles to the sarcolemma. These are called transverse tubules (T-tubules). The T-tubules connect with the extracellular space and allow interstitial fluid to flow in and through the striated muscle fiber.
b. The fiber is filled with a type of intracellular fluid called sarcoplasm.
SARCO = flesh c. Within the sarcoplasm is a tubular system called the sarcoplasmic reticulum that stores calcium, which is necessary for the muscle activation and contraction.
d. Myofilaments are found in the sarcoplasm.
MYO = muscle
FIL = thread
Myofilaments are long complexes of protein molecules, either actin or myosin. Thus, there are two main types of myofilaments: actin and myosin. The myosin filaments are thicker and have appendages known as myosin "bridges." The myosin filaments are surrounded by the thinner actin filaments.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.