musclehomeworking

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 – the fibers are spindle shaped cells, each with a single nucleus. The cells are usually arranged in parallel lines, forming sheets. Straitions are seen in cardiac and skeletal muscle but not in smooth muscle. Smooth muscle is located in the walls of hollow internal organs, and it causes these walls to contract. Contractions of smooth muscle is involuntary, occurring without conscious control. Cardiac muscle – this muscle forms the heart walls. Its fibers are generally uni-nucleated, striated, tubular, and branched, which allows the fibers to interlock at intercalated disks. The plasma membranes at intercalated disks contain at junctions that permit contractions to spread quickly throughout the heart wall Skeletal muscle – the fibers are tubular, multinucleated, and striated. They make up the skeletal muscles attached to the skeleton, they run the length of the muscle and can be quite long. Skeletal muscle is voluntary because we can decide to move a particular part of the body such as the arms or legs.

2. How do skeletal muscles work together to cause the bones to move? Skeletal muscles support the body. Skeletal muscle contraction opposes the force of gravity and allows us to remain upright. Muscles contraction assists movement in cardiovascular and lymphatic vessels. 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 Brings arm forward and across chest Deltoid Brings arm away from the side of body moves arm up and down in front Trapezius Raises scapula as when shrugging shoulders, pulls head backward biceps brachii bends forearm at elbow triceps brachii straightens forearm at elbow External oblique Compresses abdomen, rotation of trunk latissimus dorsi brings arm down and backward behind the body gluteus maximus extends thigh back quardriceps femoris straightends leg at knee, raises the thigh gastrocnemius turns foof downward, as when standing on toes;bends leg at knee

4. Define myofibrils, sarcomeres, myosin, actin myofibrils are the long muscle myofibrils make up muscle fibers. Sarcomeres are the E’s that are contracted or relaxed in the myofibrils. Myosin are the little things that pull the sarcomeres together to contract the muscle Actin are the little things that comprise the E’s or the sarcomeres.

5. Describe the structure of a sarcomere's thick and thin filaments. The sarcomere is made up of thick and thin. The actin are thin and the myosin are thick 6. Describe the sliding filament model and insert image (How does the sarcomere contract?) when the myofibrils of a muscle fiber contract, the sarcomeres shorten: the actin filaments slide past the myosin filaments toward the center.