Anatomy and Physiology Unit 5 Test Review Muscular System Chapter 6 Name 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 Skeletal Voluntary Cell description and specifics Multinucleated striated attach to the body s skeleton Cardiac Involuntary Single nucleus per cell striated branching pattern 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 fiber b Perimysium 2 Connective tissue around a bundle of fibers c Endomysium 3 A bundle of muscle fibers d Fascicle 4 Connective tissue around entire skeletal muscle e Fascia 5 On the outside of the epimysium 5 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 myosin heads 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 stimulus Contractility the ability to shorten forcibly when an adequate stimulus is received 14 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 potential within the muscle fiber 17 Explain the mechanism of muscle contraction within a sarcomere in terms of the sliding filament theory When muscle cells are activated as in the previous question the myosin cross bridges attach to the binding sites on the actin filaments and sliding begins Energized by ATP each myosin cross bridge attaches and