Muscular+System+AG

Allie Gruber Human Bio Field Period 1 September 29, 2008

Muscular System Chapter 12 pp 227-236 (New Unit called Move it)

1. What are the three types of muscles in the body and what is the function of each? Smooth muscle fibers are spindle-shaped cells, each with a single nucleus. Their function is to cause the walls of hollow internal organs to contract. Cardiac muscle forms the heart wall. Its fibers are generally uninucleated, striated, tubular, and branched, which allows the fibers to interlock at intercalated disks. Skeletal muscle fibers are tubular, multinucleated and striated. The muscle is voluntary because we can decide to move a particular part of the body.

2. How do skeletal muscles work together to cause the bones to move? In opposite pairs, contracting and releasing.

3. Pectoralis major: brings arm forward and across chest, located on top of the rib cage

Deltoid: brings arm away from the side of body and moves arm up and down in the front, located near the shoulder

Trapezius:raises scapula, and pulls head backward, located between the shoulder and spine

biceps brachii: bends forearm at elbow, located between the shoulder and the elbow

triceps brachii: straightens forearm at elbow, located on the back of the biceps brachil

External oblique: compresses abdomen and performs the rotation of the trunk, located in the lower abdomen

latissimus dorsi: brings arm down and backward behind the body, located on either side of the spine in the middle of the back

gluteus maximus: extends the thighs back, located at the bottom of the back just before the thighs

quardriceps femoris: straightens leg at the knee and raises the thigh, located above the knee on the thigh

gastrocnemius: turns foot downward as when standing on toes and bends the leg at the knee, located on the back of the leg near the calve

4. Define myofibrils, sarcomeres, myosin, actin. Myofilbrils are cylindrical in shape and run the length of the muscle fiber. Sarcomeres are arranged linearly within a myofibril whose contraction produces muscle contraction. Sarcomeres contain two types of proteins called myosin and actin. Myosin is one of two major proteins of muscle that makes up thick filaments in myofibrils of muscle fibers. Actin is the second of the two major proteins of muscle that makes up thin filaments in myofibrils of muscle fibers.

5. Describe the structure of a sarcomere's thick and thin filaments. Thick filaments are composed of several hundred molecules of the protein myosin, while the thin filament consists of two intertwining strands of the protein actin. The ATP molecule gives the myosin energy to release from the actin and contracts the muscle.

6. Describe the sliding filament model and insert image (How does the sarcomere contract?) Sliding filament model of muscle contraction is the movement of actin filaments in relation to myosin filaments. During the process the sarcomere shortens even though the filaments remain the same length. The ATP supplies energy for the muscle contraction and the myosin filaments break down the ATP, pulling actin filaments toward the center of the sarcomere.