The Muscular System

1. The Muscular System

2. MUSCULAR SYSTEM • Types of Muscle Tissue: Skeletal, Smooth, and Cardiac • Skeletal, aka “striated” • voluntary – attached to bones and under conscious, willful control. • Has the ability to contract (shorten) and thereby bring about movement

3. Cardiac Muscle • Found only in the heart • Striated • Involuntary • Cells connected by intercalated disks

4. Smooth Muscle • Not striated • Involuntary • Walls of hollow organs such as: • Stomach, urinary bladder, respiratory passages • Arranged in sheets/layers

5. Muscle Functions • Producing Movement • Maintaining Posture • Stabilizing Joints • Generating Heat • Maintaining body temperature

6. 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 connecting muscles to bones.

7. 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.

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

10. 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.

12. How do muscles contract? • Stimulated by nerve impulses to contract • Sliding Filament Theory • Muscle cell becomes excited – action potential • Flood of calcium • Myosin heads bind to thin filaments • Form “cross bridges” • Heads bend and pull thin filaments together • Muscle shortens – contracting! • Video animation of muscle contraction