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MTC BIO 210 - Anatomy Unit 5 Review Sheet KEY -2014-

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Anatomy and Physiology Unit 5 Test Review Name ______________________________Muscular System (Chapter 6) Hour ____________ Date ______________1. What are the four functions of the muscular system? Maintaining posture, generating body heat, stabilizing joints, and producing movement in conjunction with bones. 2. Fill out the chart below on muscle tissue types.Muscle Tissue Type Involuntary/Voluntary Cell description and specificsSkeletal Voluntary Multinucleated, striated, attach to the body’s skeleton. Cardiac Involuntary Single nucleus per cell, striated, branchingpattern, separated by intercalated discs. Only Found in heart. Smooth Involuntary Single Nucleus, non-striated, Spindle shaped cells, lines the walls of the visceral hollow and digestive organs. 3. Muscle cells are also known as ___Muscle Fibers_______.4. Match the words with their appropriate description.a. Epimysium 1. Connective tissue around a single muscle fiberb. Perimysium 2. Connective tissue around a bundle of fibersc. Endomysium 3. A bundle of muscle fibersd. Fascicle 4. Connective tissue around entire skeletal musclee. Fascia 5. On the outside of the epimysium5. Explain the difference between a tendon and an aponeurosis. Tendon is a rope-like structure made of dense connective tissue that attached muscles to bones. An aponeurosis is a sheet-like structure that connects skeletal muscle to skeletal muscle and also skeletal muscle to other body parts that the muscles act upon. 6. The specialized form of endoplasmic reticulum in a muscle cell is called what? What is its function?Sarcoplasmic reticulum. It stores the necessary calcium ions that are needed for muscle contraction and releases it “on demand” when muscles need to contract. 7. What is the plasma membrane of a muscle fiber called? ______Sarcolemma________________8. First put the following terms in order from outside to inside of the muscle fiber and then describe each. sarcolemma, myofibril, myofilament, sarcomere.In order from largest to smallest: Sarcolemma, Myofibril, Sarcomere, Myofilament. - The sarcolemma is the specialized plasma membrane of skeletal muscle cells. - The myofibril are the largest organelles (ribbon-like) inside the muscle cell (or muscle fiber), and have alternating bands (A and I) that give the muscle cell its striated appearance. - The sarcomere is the functional contractile unit of the muscle myofibril (where the contraction takes place), and are arranged end to end like train boxcars. - The myofilaments are protein filaments (actin: thin and myosin: thick) where the sliding occurs and where ATPase enzymes are used to break down ATP for energy.9. Explain each of the following terms: A band, I band, actin, myosin, thin filament, thick filament, myosinheads (crossbridges). Be sure to include any specifics discussed in class. Each of the structures of these parts reveals the working structure of the myofibrils. The A bands are the dark bands in alternation with the light bands or I bands which give the muscle its striated appearance. Inside each sarcomere, there are thick protein filaments (myosin filaments) and thin filaments (actin filaments) where the sliding movement occurs to create an individual sarcomere contraction. The sliding movement of the myosin heads moving along the actin filaments is what gives the sarcomere its contracting or shorter appearance (think what happens in crowd surfing, a person is moved along by all of the hands just like the myosin heads move along the thin filaments to create. Movement). A sum of all these sarcomere contractions causes muscle fiber contraction. A sum of all muscle fiber contractions will lead to overall muscle contraction. 10. What does it mean when a muscle is toned? What is occurring?It means the muscle is through a state of continual, but partial, contraction. The more a muscle is worked, the more motor units that are working on it in a systematic way. Even though the muscle is at rest, some fibers are being stimulated to contract (graded response) at times to maintain strength of muscle. 11. Explain how we build muscle endurance. We exercise muscles in order to cause more flexibility and more resistance to fatigue. We accomplish this by increasing the blood supply to the actual muscle (through exercise) and cause our muscle cells to form more mitochondria so they can store more oxygen. This also causes our heart muscle to hypertrophy and be able to pump more blood during each contraction. Also, exercise can lead to better neuromuscular coordination. 12. How does resistance lead to an increase in muscle size? Resistance is an example of isometric contraction (pitted against immovable object or one nearly so) and causes an actual increase in the size of individual muscle cells because they make more contractile thick and thin filaments (not an increase in the number of muscle cells). There is also an increase in the amount of connective tissue that is needed to reinforce the muscles. 13. Discuss the functions of irritability and contractility with regard to skeletal muscle cells.Irritability—the ability to receive and respond to a stimulusContractility—the ability to shorten (forcibly) when an adequate stimulus is received14. What is a motor unit? A Motor unit consists of one motor neuron and all of the muscle cells/fibers that it stimulates. 15. Why is it important that nerve cells (neurons) and muscle fibers are arranged into motor units? What are the advantages of this arrangement?Motor units consist of a nerve cell and all of the skeletal muscles it stimulates. This arrangement allows many muscle fibers (cells) to be stimulated to contract at once, allowing for coordinated voluntary muscle movements.16. Describe how an action potential is initiated in a muscle cell. Mention the terms motor neuron, neuromuscular junction, synaptic cleft, neurotransmitter, acetylcholine, sarcolemma, Na + ions, and electric current (action potential) in your answer.The motor neuron meets the muscle fiber at the neuromuscular junction ; the space between the nerve and muscle forms the synaptic cleft . When the nerve impulse reaches the end of the motor neuron, a chemical neurotransmitter called acetylcholine is released into the synaptic cleft. When acetylcholine reaches the sarcolemma of the muscle fiber on the other side, Na + ions rush in, generating an electric current called an action


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