Muscle Study Guide

1. Describe how connective tissue is part of the structure of a skeletal muscle.

* An individual skeletal muscle is separated from adjacent muscles and held in position by layers of dense connective tissue called fascia.

* The fascia surrounds each muscle and may project beyond the ends of the muscle fiber to form a cordlike tendon.

* Aponeuroses are broad fibrous sheets of connective tissue which may attach to bone or the coverings of adjacent muscles. They sometimes intertwine with tendon fibers.

* Epimysium= the layer of connective tissue that closely surrounds a skeletal muscle.

* Perimysium= another layer of connective tissue that extends inward from the epimysium, and separated the muscle tissue into small sections.

* These sections contain bundles of skeletal muscle fibers called fascicles. Each muscle fiber within a fascicle lies within a layer of connective tissue in the form of a thin covering called endomysium.

2. Major parts of the skeletal muscle fiber.

* The sarcoplasm (cytoplasm) has abundant, parallel threadlike structures called myofibrils. The myofibrils play a fundamental role in the muscle contraction mechanism. They consist of 2 kinds of protein filaments:

A. Thick filaments composed of the protein myosin

B. Thin filaments composed of the protein actin

* The organization of these filaments make light and dark striations characteristic of skeletal and cardiac muscle. The striations form a repeating pattern of units called sarcomeres. Muscle fibers are basically collections of sarcomeres.

* The striation pattern of skeletal muscle has 2 major parts:

A. The I bands (the light bands) are composed of thin actin filaments held directly to structures by Z lines, which appear in the center of I bands.

B. A bands (the dark bands) are compsed of thick myosin filaments overlapping thin actin filaments. A bands are made up of the overlapping region AND also a slightly lighter central region, the H...