Review Sheet Exam 3 11 08 2010 o Each muscle fiber skeletal muscle cell is wrapped in a delicate connective tissue membrane called endomysium o Fascicle consists of a group of endomysium covered muscle fibers wrapped in a coarse connective tissue membrane called o Skeletal muscle consists of a group of fascicles wrapped in a tough connective tissue membrane called epimysium o Fascicle consists of a group of endomysium covered muscle fibers wrapped in a coarse connective tissue membrane called Muscular System 1 Define Endomysium Perimysium perimysium Epimysium Fascicles perimysium Tendons o Sarcolemma Sarcoplasm o plasma membrane of muscle fiber o Cytoplasm of the muscle fiber Sarcoplasmic Reticulum o Specialized smooth endoplasmic reticulum that stores releases calcium into the sarcoplasm the expanded ends of sarcoplasmic reticulum are called terminal cisternae Myoglobin o A red pigment that binds and stores oxygen Sarcomere o Structural units of skeletal muscle each skeletal muscle is composed of repeated units arranged end to end called sarcomeres o The distance between two successive Z lines a sarcomere o Middle region of the A band not overlapping with the thin o Anchor the thin filaments Z line H zone A band I band Triad filaments o Thick filament o Regions of the thin filaments not overlapping with the A band o Composed of a transverse tubule in between 2 terminal cisternae Terminal cisterna Ttubule Terminal cisterna o Function For the release of calcium ions into the sarcoplasm when the sarcolemma depolarizes Motor Unit o 2 Describe the neuromuscular junction What is the motor end plate Neuromuscular junction o The junction between the axonal terminal of a motor neuron and a skeletal muscle fiber separated by a small space called the neuromuscular cleft synaptic cleft o Each muscle fiber has only one neuromuscular junction Motor end plate o The highly folded region of the sarcolemma of the muscle fiber at the neuromuscular junction is called the motor end plate express acetylcholine receptors on the surface o A motor neuron and all the muscle fibers it innervates via its axonal terminals is called a motor unit motor units come in different sizes small medium large 3 Name the 3 proteins in a thin filament What is the function of tropomyosin in a relaxed skeletal muscle Actin o Double helical structure that forms the core of the thin filament contains binding sites for myosin o A rod shaped regulatory protein that spirals around the actin and blocks myosin binding sites on actin in a relaxed skeletal Tropomyosin muscle o Troponin Three complex protein consisting of TnC binds calcium ions TnT binds to tropomyosin TnI inhibitory subunit that binds to actin The function of tropomyosin in a relaxed skeletal muscle is spirals around the actin and blocks myosin binding sites on actin Name the 3 subunits of troponin Which troponin subunit is bound to actin TnC binds calcium ions TnT binds to tropomyosin TnI inhibitory subunit that binds to actin 4 How are the myosin heads activated Myosin heads are activated when the myosin heads are attached by ADP Pi resulting from ATPase hydrolysis of ATP into ADP Pi 5 Describe skeletal muscle contraction Size of motor units activated larger motor units generate more force than smaller motor units Number of motor units activated force increases as the number of motor units activated increases Recruitment smaller motor units are activated first followed by larger motor units Frequency of skeletal muscle activation force increases as the rate of stimulation by motor neurons increases The length of the sarcomeres prior to contraction sarcomeres at the optimum length generate the maximum force sarcomere length below the optimum length shortened sarcomeres results in decreased force sarcomere length greater than the optimum length stretched sarcomeres results in decreased force of contraction 6 Give the role of ATP in muscle contraction ATP is hydrolyzed by ATPase to produce ADP and Pi to activate the ATP is required for crossbridge detachment ATP is required for the sequestration of calcium ions back into the SR for storage active transport Differentiate between muscle fatigue and rigor mortis Muscle fatigue o Muscle fatigue is a physiological inability of a stimulated skeletal muscle to contract due to ATP deficit rate of ATP production lags behind ATP demand Rigor mortis o Lack of new ATP results in skeletal muscle contracture termed rigor mortis occurs when an individual dies and ATP synthesis ceases actin and myosin are irreversibly cross linked and skeletal muscles remain contracted 7 Define the sliding filament mechanism list structures that a shorten b remain the same when a skeletal muscle contracts States that the sliding of the thin filaments past the A bands results in muscle contractions According to this mechanism when a muscle contracts there is more overlap between the thin filaments and the A bands o H zone decreases or disappears o I bands decrease or disappear o Sarcomere length shortens skeletal muscle shortens contracts However the lengths of the A bands and the thin filaments remain the same they do not shorten why 8 Discuss the factors that affect the strength of skeletal contraction 9 Name and give the characteristics of the 3 types of skeletal muscle fibers Which type is fatigable and why Which type is also known as red fiber and Three major types of muscle fiber types based on o Speed of contraction two types Slow fibers and fast fibers due to the speed at which Myosin ATPase hydrolyzes ATP o Major Pathway for ATP production two ways Aerobic respiration oxidative fibers types Anaerobic respiration using more glycogen glycolyic o Based on the above criteria there are three major skeletal fiber types muscles types Slow Oxidative Fibers Fast Oxidative Fibers Fast Glycolytic Fibers 10 Define isotonic and isometric contractions Isotonic contractions o Muscle shortens at a relatively constant force isotonic same force force generated by skeletal muscle exceeds the weight so the skeletal muscle contracts and work is done such as lifting the weight Isometric contractions o Force tension generated by the muscle is increasing at a constant muscle length isometric same length occurs when the weight exceeds the force generated by the muscle 11 Compare and contrast the structures and mechanism of contraction for skeletal and smooth muscles What is the function of calmodulin in smooth muscle contraction 12 Name the structures present in
View Full Document
Unlocking...