Muscle Physiology

How They Work

Muscle Fibers

Muscles are made of many individual cells called fibersThe Fascia connects the individual fibers to form a muscle and it separates muscles from each other.

Muscles have 3 layers of C.T.

Epimysium: outermost layer that surrounds the whole musclePerimysium: Surrounds and separates the fasciclesEndomysium: surrounds each individual muscle fiber

Muscle fiber membrane:The plasma membrane of a muscle fiber is called the sarcolemmaThe cytoplasm is called the sarcoplasm

Inside the sarcolemma

The many parallel fibers inside the muscle cell are called myofibrils.Each myofibril is made of protein filaments called myofilaments.The thin filaments are actin.The thick filaments are called myosin.

What is a sarcomere?

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 the SARCOMERE.

The arrangement of the sarcomeres produces the familiar striations of skeletal muscle.