Muscular+System+WG

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: type of muscle that has fibers spindle-shaped cells, each with a single nucleus. The cells are usually arranged in parallel lines, forming sheets. Contraction of smooth muscle is involuntary, occurring without conscious control. Cardiac: it forms the heart wall. Its fibers are generally uninucleated, striated, tubular, and branched, which allows the fibers to interlock at intercalated disks. Skeletal: tubular, multinucleated, and striated. They also make up the skeletal muscles attached to the skeleton. It is also 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? Our bones move because muscle contraction accounts not only for the movement of arms and legs but also for movements for our eyes, facial expression, and breathing. 3. Insert an image of the major muscles in the body like the one on page 231. You will need to know the location and function of the following (write the function next to the name -- see page 231)

Pectoralis major: It brings the arm forward and across the chest. Deltoid: It brings the arm away from the side of the body, and it moves the arm up and down in eblow. Trapezius: Its job is to lift the scapula, as when shrugging shoulders; it pulls the head back. biceps brachii: It bends the forearm at the elbow. triceps brachii: It straightens forearm at elbow. External oblique: the external obliqe compresses the abdomen; rotation of trunk latissimus dorsi: latissimus dorsi brings the arm down and backward behind the body. gluteus maximus: Gluteus maximus extends the thigh back. quardriceps femoris: It straightens the leg at the knee, and raises the thigh. gastrocnemius: It turns the foot downward, as when standing on your toes, it also bends the leg and knee.

4. Define myofibrils: Very small, and are contractile portions of the muscle fibers.

Sarcomeres: It extends between two dark lines called the Z lines. A sarcomere contains two types of protein myofilaments.

Myosin: Myosin is thick filaments that are made up of protein.

Actin: Actin is a thin filament that is made up of protein.

5. Describe the structure of a sarcomere's thick and thin filaments. Thick filaments are composed of several hundred molecules of the protein myosin. The cross-bridges occur on each side of a sarcomere but not in the middles. Thin filaments consist of two intertwining strands of the protein actin. Two other proteins, called tropomyosin and tropnin, also play a role.

6. Describe the sliding filament model and insert image (How does the sarcomere contract?)

Sliding filament is the movement of Actin filaments in the relation to myosin filaments. During the sarcomere contraction, the sacomere shortens, and even though the filaments themselves remain the same length.