Motor Units and Neuromuscular Junctions
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Questions and Answers

What is a common indication of gross pathologic changes in muscles?

  • Muscle atrophy
  • Muscle hypertrophy
  • Pale streaking of muscle (correct)
  • Muscle spasm

    • What is a possible cause of dark red mottling of skeletal muscle?

  • Muscle parasites
  • Muscle hypertrophy
  • Myofiber necrosis
  • Congestion or hemorrhage (correct)

    • What is the purpose of concentric needle EMG studies?

  • To diagnose myofiber necrosis
  • To search for abnormal spontaneous activity (correct)
  • To diagnose muscle parasites
  • To diagnose neuromuscular disease

    • What is a characteristic of denervated muscle?

    <p>Altered sodium channel activity in the membrane</p> Signup and view all the answers

    What can be a sign of neuromuscular disease?

    <p>All of the above</p> Signup and view all the answers

    What can be grossly visible in muscle as discrete, round to oval, pale and slightly firm zones?

    <p>Muscle parasites</p> Signup and view all the answers

    What is an indication of a healthy muscle in EMG studies?

    <p>A flat line</p> Signup and view all the answers

    What is a type of abnormal spontaneous activity found in denervated muscle?

    <p>All of the above</p> Signup and view all the answers

    What is the term for muscle fiber necrosis?

    <p>Myodegeneration</p> Signup and view all the answers

    Which of the following is a muscle disease characterized by inflammation?

    <p>Inflammatory myopathy</p> Signup and view all the answers

    What is the term for an immune-mediated inflammatory myopathy confined to masticatory muscles in dogs?

    <p>Masticatory myositis</p> Signup and view all the answers

    What is the term for passage of urine containing large amounts of myoglobin?

    <p>Myoglobinuria</p> Signup and view all the answers

    What is the term for muscle disease caused by defects in muscle energy metabolism?

    <p>Metabolic myopathy</p> Signup and view all the answers

    What is the term for muscle necrosis caused by a single nonpersistent injury?

    <p>Monophasic muscle necrosis</p> Signup and view all the answers

    What is the term for a muscle fiber?

    <p>Myofiber</p> Signup and view all the answers

    What is the term for an inherited, progressive myopathy characterized by ongoing myofiber necrosis and regeneration?

    <p>Muscular dystrophy</p> Signup and view all the answers

    What is the outermost layer of connective tissue that encases an entire muscle?

    <p>Epimysium</p> Signup and view all the answers

    What is the function of the sarcoplasmic reticulum in myofibers?

    <p>To sequester calcium ions necessary to initiate actin and myosin interaction</p> Signup and view all the answers

    What is the term for the sarcolemmal invaginations that traverse the cell and allow rapid dispersion of a sarcolemmal action potential?

    <p>T tubules</p> Signup and view all the answers

    What is the arrangement of actin and myosin filaments in muscle cells?

    <p>Sarcomeric arrangement</p> Signup and view all the answers

    What is the function of the connective tissue framework in skeletal muscle?

    <p>To store and relay force generated by myofiber contraction</p> Signup and view all the answers

    What is the term for the structure formed by the terminal cisternae of two adjacent sarcomeres and the T tubule?

    <p>Triad</p> Signup and view all the answers

    What is the outer layer surrounding each myofiber?

    <p>Endomysium</p> Signup and view all the answers

    What is the term for the thin layer of connective tissue containing capillaries that surrounds each myofiber?

    <p>Endomysium</p> Signup and view all the answers

    What is a result of overloading of hypertrophied fibers?

    <p>Segmental necrosis of the hypertrophied fibers</p> Signup and view all the answers

    What is the term for the process by which a myofiber divides into one or more smaller-diameter fibers?

    <p>Fiber splitting</p> Signup and view all the answers

    What is a type of cytoarchitectural change that can occur within myofibers?

    <p>Fiber splitting</p> Signup and view all the answers

    What is the functional significance of many of the myofiber cytoarchitectural changes?

    <p>Unknown</p> Signup and view all the answers

    What can be a manifestation of processes leading to myofiber necrosis?

    <p>Vacuolar change</p> Signup and view all the answers

    What is the normal location of myonuclei in mature myofibers in domestic animals?

    <p>Peripherally, just beneath the sarcolemma</p> Signup and view all the answers

    What can be caused by abnormal storage of carbohydrate or lipid?

    <p>Vacuolar change</p> Signup and view all the answers

    What is the term for muscle disease characterized by vacuolar change?

    <p>Vacuolar myopathy</p> Signup and view all the answers

    What can be a result of fiber atrophy, fiber hypertrophy, or both?

    <p>Chronic myopathic change</p> Signup and view all the answers

    What is the term used to imply a reduction in the volume of the muscle as a whole or a reduction in the diameter of a myofiber?

    <p>Atrophy</p> Signup and view all the answers

    What is a cellular process that can be activated to result in muscle atrophy?

    <p>Both A and B</p> Signup and view all the answers

    What type of fibers are most likely to atrophy under various circumstances?

    <p>Type 2 fibers</p> Signup and view all the answers

    What is a signaling molecule involved in muscle atrophy?

    <p>Tumor necrosis factor-alpha (TNF-α)</p> Signup and view all the answers

    What is the term used to describe the positive reaction of denervated fibers in alkaline phosphatase and nonspecific esterase preparations?

    <p>Lysosomal activation</p> Signup and view all the answers

    What is a cause of muscle fiber atrophy?

    <p>Denervation</p> Signup and view all the answers

    What is often required for a definitive diagnosis of muscle fiber atrophy?

    <p>Fiber typing</p> Signup and view all the answers

    What is a characteristic of a regenerating fiber?

    <p>Basophilia due to increased RNA content</p> Signup and view all the answers

    What is a common finding in chronic myopathic change?

    <p>Fiber splitting</p> Signup and view all the answers

    What is a cytoarchitectural change associated with chronic myopathic change?

    <p>Internal nuclei</p> Signup and view all the answers

    What is a consequence of fibrosis in locomotory muscles?

    <p>Altered gait</p> Signup and view all the answers

    What is a characteristic of muscle giant cells?

    <p>Large, multinucleate cells</p> Signup and view all the answers

    What is a consequence of collagen deposition in muscle?

    <p>Reduced muscle contractility</p> Signup and view all the answers

    What is a feature of regenerating fibers during differentiation?

    <p>Appearance of longitudinal and cross-striations</p> Signup and view all the answers

    What is the usual location of muscle nuclei in normal muscle fibers?

    <p>Peripherally, just under the sarcolemma</p> Signup and view all the answers

    What is the cause of phosphofructokinase deficiency in dogs?

    <p>Point mutation in the muscle isoenzyme of phosphofructokinase</p> Signup and view all the answers

    Which breed of cat is prone to glycogenosis type IV?

    <p>Norwegian Forest cats</p> Signup and view all the answers

    What is the result of absence of erythrocyte phosphofructokinase in dogs?

    <p>Hemolysis during periods of increased respiratory activity</p> Signup and view all the answers

    What is the mode of inheritance of glycogenosis type IV in Norwegian Forest cats?

    <p>Autosomal recessive</p> Signup and view all the answers

    What is the result of myophosphorylase deficiency in sheep?

    <p>Glycogen storage myopathy</p> Signup and view all the answers

    What is the characteristic of affected cats with glycogenosis type IV?

    <p>All of the above</p> Signup and view all the answers

    What is the test used to detect affected animals and carriers of glycogen storage myopathy?

    <p>Polymerase chain reaction assay</p> Signup and view all the answers

    What is the outcome of phosphofructokinase deficiency in dogs?

    <p>Skeletal muscle upregulates expression of the liver isoenzyme of phosphofructokinase</p> Signup and view all the answers

    What is the primary cause of most inherited myotonic conditions?

    <p>Abnormal ion channel function</p> Signup and view all the answers

    Which of the following is a characteristic of metabolic myopathies?

    <p>All of the above</p> Signup and view all the answers

    What is the inherited pattern of glycolytic, glycogenolytic, and nonmitochondrial DNA-encoded enzyme defects?

    <p>Autosomal recessive</p> Signup and view all the answers

    What is the consequence of a deficiency in a glycolytic or glycogenolytic enzyme?

    <p>Accumulation of glycogen and glycogen-related proteoglycans</p> Signup and view all the answers

    Which of the following types of glycogenoses cause glycogen accumulation in muscle?

    <p>Types II, III, IV, V, and VII</p> Signup and view all the answers

    What is the inheritance pattern of defects involving mitochondrial DNA-encoded enzymes?

    <p>Mitochondrial inheritance through the dam</p> Signup and view all the answers

    What is the primary function of sarcolemmal ion channels in muscle cells?

    <p>All of the above</p> Signup and view all the answers

    What is a common clinical sign of metabolic myopathies?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is a characteristic of the progressive inherited myopathy described in the text?

    <p>Atrophy and hypertrophy of the myofibers, along with myopathic features</p> Signup and view all the answers

    What is the age at which clinical signs of neuromuscular weakness occur in the described disorder?

    <p>1 month</p> Signup and view all the answers

    What is the term for the protein complex affected in other canine muscular dystrophies?

    <p>Sarcoglycan complex</p> Signup and view all the answers

    What is the age at which affected dogs exhibit signs of neuromuscular disease in sarcoglycan defects?

    <p>1 year</p> Signup and view all the answers

    What is the mutation responsible for X-linked myotubular myopathy?

    <p>Mutation in the MTM1 gene</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the progressive inherited myopathy described in the text?

    <p>Ongoing progressive myofiber necrosis and regeneration</p> Signup and view all the answers

    What is the impact of this progressive inherited myopathy on the affected animals?

    <p>Animals producing affected lambs should not be rebred</p> Signup and view all the answers

    What is the significance of the age of the animal in the appearance of the muscle in this disorder?

    <p>The appearance changes over time, from pale and lacking tone to firm, atrophic, and pale gray to almost white</p> Signup and view all the answers

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