| ACT #1: Introduction to the Muscular System
Muscles make our skeletons move, but they also move other parts of the body. For example, the heart is a muscle and muscles in the digestive tract help digest food. A) What are three types of muscle cell? 1) 2) 3) B) Copy this down please: Smooth muscle is found mainly in the walls of internal organs and is involuntary which means �.(fill in the rest). C) Skeletal muscles mainly move joints of the body and may be attached to bones by� In order to cause movement, muscles must be attached to bones in two places. The attachment at the stationary point is called the ORIGIN, while the movable point is called the insertion of the muscle. Since muscles contract and relax (but not stretch themselves), skeletal muscle must work in pairs in order to move bones. D) A muscle that bends a joint is called a FLEXOR. An example would be the _____ muscle. Pg. 546 Fig. 33.13 E) A muscle that straightens a joint is called an EXTENSOR. An example would be the _____ muscle. F) Skeletal muscle is voluntary which means� G) And lastly, cardiac muscle is found in one organ of the body, the _____. ACT #2: Smooth Muscle Observation Examine a microscope slide labeled �Involuntary Muscle�. You will have to look over the slide with the scanning lens to find isolated cells. Also, some of the cells are in �cross-section�, you don�t want those! Look for cells in the area that appears as a wavy lines. A) The smooth muscle cell is spindle-shaped (an oval with pointed ends) and the nucleus stains more deeply than the sarcoplasm. Sketch the muscle under high power labeling the sarcoplasm, nucleus, and cell membrane. B) How many nuclei does each cell contain? Notice the absence of any STRIATIONS (cross banding) on these cells. This is why the muscles are �smooth�. This primitive type of contractile cell is abundant in the walls of digestive tract and other internal organs. Its contractions are slow and untiring. ACT #3: Skeletal Muscle Observation Examine a microscope slide labeled �Striated Muscle�. Once again observe these muscle fibers in longitudinal section. A thin, transparent membrane, the SARCOLEMMA is not visible unless it had become accidentally separated. A sarcolemma is absent from smooth muscle cells. Try to distinguish the small contractile myofibrils which are arranged parallel to one another and longitudinally within a skeletal muscle fiber. Each myofibril has alternating dark and light zones along its length. This is why skeletal muscles are also called STRIATED MUSCLES. (A) Make a sketch on the high power of a striated muscle fiber. Label the striations, nucleus, sarcolemma. (B) What is the general function of skeletal muscles in the vertebrate body? ACT #4:Cardiac Muscle Observation Examine a microscope slide of a stained cardiac muscle. The cells of this tissue are interconnected to form a branching network, which cannot be completely isolated into separate fibers. Make a sketch on high power. Cardiac muscle fibers are generally smaller in diameter than skeletal muscle fibers and the striations may be less distinct. Cardiac muscle fibers are covered by a sarcolemma and contractions of this tissue are rhythmic, untiring, and involuntary. Copy down and complete this chart by using check marks: Summary of muscle types Smooth Skeletal Cardiac Found in digestive organs. Attached to skeleton In the heart Has striations Many nuclei around edge Single central nucleus Involuntary Voluntary Slow, untiring contractions Rhythmic, untiring contractions Rapid contractions but easily fatigued. |