muscular+systemdw

Muscular System Chapter 12 pp 227-236 (New Unit called Move it) DeMarcus Waggoner 1. What are the three types of muscles in the body and what is the function of each? Smooth Muscle- it is located in the walls of hollow internal organs, and it causes these walls to contract involuntarily. (less fatigued than other muscles) Cardiac Muscle- Cardiac muscle forms the heart. Cardiac fibers relax completely between contractions which prevents fatigue. Contractions of the cardiac muscle is rhythmical; it occurs without outside nervous stimulation and without conscious control. (so it is also an involuntary muscle) Skeletal Muscle-They run the lengths of the muscle and can be quite long. Skeletal muscle is voluntary because its contraction can be consciously stimulated and controlled by the nervous system. They have numerous functions.

2. How do skeletal muscles work together to cause the bones to move? Our skeletal muscles are attached to the skeleton, and their contraction causes the movement of bones and joints.

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 Flexes and adducts shoulder and arm ventrally (pulls arm across chest) Deltoid Abducts and raises arm at shoulder joint Trapezius Extends head; raises and adducts shoulders dorsally biceps brachii Abducts and raises arm at shoulder joint triceps brachii Eatends forearm External oblique Rotates trunk latissimus dorsi Extends and adducts shoulder and arm dorsally (shrugging shoulders) gluteus maximus Exends thigh (form buttocks) quardriceps femoris Extends leg gastrocnemius Flexes leg and foot (tiptoeing 4. Define myofibrils, sarcomeres, myosin, actin Myofibrils- A bundle of myofilaments that contracts Sarcomeres- The units of the skeletal muscle fibers that are formed by the placement of myofilaments within units of myofilrils. Myosin-Thick filaments made of protein Actin-thin filaments made of protein 5. Describe the structure of a sarcomere's thick and thin filaments. Thick Filaments is composed of several hundred molecules of protein myosin. Eachs myosin molecule is spread like a golfclub, with the straight portion os the muscle ending in a double globular head, or crossbridge. The cross-bridge occur on each side os a sarcomere but not in the middle. Primarialy a Thin filament consist od two intertwining strands of the protein actin. Two other proteins called tropamyosin and troponin, also play a role. 6. Describe the sliding filament model and insert image (How does the sarcomere contract?)

During the sliding process, the sarceoere shortens, even though the filaments themselves remain the same length. ATP supplies the energy for muscle contractions. Although the actin filaments slide past the myosin filaments it is the myosin filaments that do the work. Myosin filaments break down ATP and have cross-bridges that pull the actin filaments toward the center of the sarcomere.