HB+Muscular+System

=Muscular System=

What are the three types of muscles in the human body?

 * Humans have three types of muscle tissue. Smooth Muscle is involuntary and occurs in walls of internal organs. Cardiac Muscle is involuntary and occurs in walls of the heart. Skeletal muscle is voluntary, contains bundles of muscle fibers called fascicles, and is usually attached by tendons to the skeleton.

List and discuss the functions of muscles.

 * Skeletal Muscle has several functions. The help maintain posture, provide movement and heat, protect underlying organs.

Give an example that illustrates how muscles work in antagonistic pairs.

 * When achieving movement, some muscles are prime movers, some are synergists, and others are antagonists.

Describe the microscopic anatomy of muscle fiber and explain the sliding filament model of muscle contraction.

 * Muscle fibers contain myofibrils, and myofibrils contain actin and myosin filaments. Muscle contraction occurs when sarcomeres shorten and actin filaments slide past myosin filaments.

Describe the structure and function of the neuromuscular junction.

 * Nerve impulses travel down motor neurons and stimulate muscle fibers at neuromuscular junctions.

Describe the events as myosin pulls actin toward the center of the sarcomere.

 * Myosin filaments break down ATP and attach to actin filaments, forming cross-bridges. When ADP and P are released, cross-bridges change their positions. This pulls actin filaments to the center of a sarcomere.

Contrast a muscle twitch with summation and tetanus.

 * When a motor unit is stimulated by infrequent electrical impulses, a single contradiction occurs that lasts only a fraction of a second, its called a muscle twitch. After relaxing completely, Summutation is increased in the muscle contraction until maximal sustained contraction, called tetanus.

What is muscle tone, and how is it maintained?

 * In the body, a continuous slight tension called muscle tone is maintained by muscle motor units that take turns contracting.