MUSCULAR SYSTEM

Types of Muscle Tissue: Skeletal, Smooth, and Cardiac

* Skeletal, aka “striated”, aka “voluntary” – attached to bones and under conscious, willful control. Has the ability to contract (shorten) and thereby bring about movement

I. Muscle and Muscle Fiber Structure: A muscle is composed of many muscle fibers (muscle fiber = muscle cell). The individual muscles are separated from each other and held in place by a covering called the FASCIA. This fascia also forms TENDONS and APONEUROSES connecting muscles to bones and muscles to muscles.

A muscle also contains 3 different layers of connective tissue: Epimysium – outermost layer, surrounds entire muscle Perimysium – separated and surrounds the FASCICLES (bundles) of muscle fibers Endomysium – surrounds each individual muscle fiber

Skeletal muscle fibers contain numerous nuclei and mitochondria

The muscle fiber membrane is called the SARCOLEMMA and the cytoplasm is called the SARCOPLASM. Within the sarcoplasm are many parallel fibers known as MYOFIBRILS

[pic]

Each myofibril is made of many protein filaments called MYOFILAMENTS. There are two types: MYOSIN – thick filaments ACTIN – thin filaments

Actin and Myosin filaments are arranged in an overlapping pattern of light (“I” bands) and dark (“A” bands). In the middle of each “I” band is a line called a “Z” line. The section of a myofibril from one Z-line to the next Z-line is called a SARCOMERE. The arrangement of these sarcomeres next to each other produces the STRIATIONS of the skeletal muscle fibers.

Each Myofibirl is surrounded by a network of membranous channels called SARCOPLASMIC RETICULUM. Other “tubes”

[pic] between the actin and myosin filaments ( the filaments slide between