Muscular+System-RJ

Muscular System (1) What are the three types of muscles in the human body? (Describe and include pictures) (2) List and discuss the functions of muscles. Smooth- Controls actions that are involuntary Skeletal- Controls actions that voluntary** (3) Give an example that illustrates how muscles work in antagonistic pairs. (pictures good) (4) Describe the microscopic anatomy of muscle fiber and explain the sliding filament model of muscle contraction. (long answer)
 * Skeletal, Cardiac, and Smooth muscles**
 * Cardiac- Heart is made of cardiac muscles
 * Tris and Bis**
 * The muscle fiber has many parts to it. It is made up of endoplasmic reticulum, sarcoplasmic recticulum, sarcoplasm, and cytoplasm. It also has a unique system called the T system. The sarcolemma forms T tubules penetrate into the cell so that they come into contact with expanded portions of the sarcoplasmic reticulum which store calcium. Calcium is essential for muscle contractions.

Sliding filament model is the movement of actin filaments in relation to myosin filaments. When muscles are stimulated the impulse travel down down the T tubule and the calcium is released from the S.R. The muscle fiber contracts as the sarcomeres in the myofibrils shorten. When it does the actin filaments slide past the myosin filaments and approach each other. This causes the I band to shorten, the Z line to move inward, and the H zone to almost or completely disappear.** (5) Describe the structure and function of the neuromuscular junction. (6) Describe the events as myosin pulls actin toward the center of the sarcomere. (7) Contrast a muscle twitch with summation and tetanus. (8) What is muscle tone, and how is it maintained?
 * The axon of one motor neuron can stimulate from a few to several muscle fibers of a muscle because each axon has several branches. Each branch of an axon ends in an axon terminal that lies in close proximity to the sarcolemma of a muscle fiber. A small gap, called a synaptic cleft, separates the axon terminal from the sarcolemma.**
 * The thick filaments are made up of a protein called myosin and the thin filaments are made up of a protien called actin. The I band is light colored b/c it contains only actin filaments attached to a Z line. The dark regions of the A band contain overlapping actin and myosin filaments, and its H zone has only myosin filaments.**
 * Muscle twitch with summation is a muscle contraction that stays contracted until it reaches its maximal contraction and then releases. Tetanus is constant muscle contraction and the muscle never contracts.**
 * When some motor units are always contracted but not enough to cause movement the muscle is firm and solid.**