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56 Cards in this Set
- Front
- Back
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Which types of muscle are striated?
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Skeletal and Cardiac. Smooth muscle is not striated.
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Where are nuclei located in the muscle fiber?
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Periphery, just below the sarcolemma
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clusters of muscle fibers within the muscle, surrounded by the fibrocollagenous perimysium
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fascicle
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Where are the vessels, lymphatics, and nerves located in the muscle?
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Perimysium
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Where are capillaries and individual nerve axons located in the muscle?
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Muscle fiber (myofiber,) which is an individual muscle cell surrounded by endomysium
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Which muscle component fills up 80% of the volume of the sarcoplasm?
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Myofibril, which are the contractile filaments that are divided into units called sarcomeres
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Components of a myofilament?
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Thick and Thin filaments arranged within a sarcomere
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Thin filaments are made from which protein?
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Actin
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Thick filaments are made from which protein?
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Myosin
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alpha actinin makes up which part of the sarcomere?
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Z line, the end that anchors the thin filaments
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What is the name of the segment of the sarcomere that contains thick filaments only?
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H band, the lighter band in the center of the A band. The H band contains the darkly stained M line.
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Which line in the sarcomere functions as the anchor for the thick filaments?
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M line, in the center of the lightly stained H section. Contains the protein myomesin
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Which region of Sarcomere contains only thin filaments?
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I band
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Which region has an overlap of thick and thin filaments?
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A band
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How are adjacent myofibrils attached to each other?
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desmin, which binds to Z line with the protein plectin
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Which protein maintains the position of the thick filaments?
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titin, which also exerts tension on the sarcomere in the relaxed state
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Progressive muscle weakness, degeneration, atrophy, early onset (when child learns to walk)
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Duchenne Muscular Dystrophy, absence of Dystrophin protein
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Less severe form of muscular dystrophy, closely related to Duchenne MD, later onset (age 11-25), partial but insufficient dystrophin function.
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Becker Muscular Dystrophy
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More than a dozen inherited diseases characterized by progressive loss of muscles in the shoulders and hips, symptoms usually begin appearing in teenage years.
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Limb-Girdle Muscular Dystrophy
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Group of 6 muscle diseases affecting muscles of the forearms, lower legs, feet, and hands, slow progression, onset 40-60 years.
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Distal MD, one form is Miyoshi myopathy, which has lack of dysferlin
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Group of autosomal recessive disorders, evident before age of 2, affect both males and females, some forms (1/2 of cases) associated with lack of laminin alpha2 chain (merosin), a CT protein that binds dystroglycan)
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Congenital MD
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What is most indicative microscopic feature of muscular dystrophy?
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variability in size of muscle fibers, lots of connective tissue, centrally located nuclei. Necrotic fibers, infiltration of fat cells, and macrophages are also seen.
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links actin to dystroglycan
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dystrophin
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adapter protein links to signaling proteins
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syntrophin
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links nitric oxide synthase to complex
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dystrobrevin
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transmembrane glycoprotein complex, linking dystrophin to extracellular matrix
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dystroglycan
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transmembrane glycoprotein complex, linking mechanical stress and signaling pathways
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sarcoglycan
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may stabilize dystrophin complex
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sarcospan
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links basement membrane to dystroglycan complex
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merosin
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Explain the Dysferlin mediated repair model
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When the sarcolemma breaks, Ca rushes in and activates Calpain, which binds to Dysferlin. The Dysferlin recruits vesicles to repair the damaged site.
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What are triads, and what are they made from?
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Made from SR cisternae/t-tubule/SR cisternae, located at the junction of the A band and I band.
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What do T-Tubules do?
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When excited, open electrically sensitive Ca ion channels in the SR, which them flood the sarcoplasm and lead to muscle contraction
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What are the functions of the human skeleton?
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Mechanical framework, structure, protection, mineral repository, hematopoesis
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What is Wolff's Law?
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Bone follows its function; as the use changes, the structure can adapt.
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The diaphysis(shaft) is primarily made up from?
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Cortical or Haversian bone
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The internal structure of metaphysis and flat bones is made from?
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Cancellous, Trabecular, or Spongy bone.
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What are the two main components of bone?
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Type One Collagen (tensile strength) and Hydroxyapatite (compressive strength). It is first laid done in osteoid, and then mineralized over several weeks.
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Cortical or Haversian bone characteristics
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Makes up external shell of each bone, 5-10% porosity, longitudinally organized, 5% turnover/year
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Cancellous, Trabecular, or Spongy bone characteristics
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Makes up the inside of the metaphyses of bones and flat bones,75-95% porosity, uniformally organized, 25% turnover/year
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What are the two types of bone tissue?
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Lamellar and Woven. Most of the bone in humans is Lamellar, which is collagen and mineral organized into orthogonal layers, and grows very slowly. Woven bone has more disorganized collagen fibers, forms quickly like in fracture repair, and is more mineralized than lamellar bone
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Which type of bone has Resorption cavities?
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Haversian bone
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Which type of bone has marrow-filled pores?
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Cancellous bone
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Which is greater in bone: compressive strength or tensile?
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Compressive
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Which is greater in bone: transverse or longitudinal strength?
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Longitudinal
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What is endochondral ossification?
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Most of the skeleton forms from a cartilage precursor. Ossification starts in the mid-diaphysis and secondary ossification occurs in the epiphyses (this area is called the physis, or growth plate.) Osteoblasts replace the cartilage for bone
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At what age do bones reach maturity?
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14-16 for girls and 16-18 for boys
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How do Osteoclasts form?
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Through fusion of monocytes. They are large multinucleated cells which resorb bone, leaving a moth-eaten appearance called "Howship's Lacuna"
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Describe the shape and structure of Osteoblasts
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Bone forming cells cuboidal shape, mononuclear. Serve as a means of intercelluar communication
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What are osteocytes?
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They are former osteoblasts which get trapped in the extracellular matrix, and reside in small shells called lacunae, communicate across larger distances via cell process at the gap junctions, and may play a role in mechanical adaptation
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What are bone lining cells?
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Flattened, retired osteoblasts that remain connected to osteocytes and pre-osteoblasts. Activate new remodeling and play a role in ion exchange.
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How long does Haversian remodeling take?
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4 months. First a cone of osteoclasts hollows out a tunnel which is filled by osteoblasts, which deposit layers of osteoid which mineralize over time. No net change in the amount of bone.
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Chronic Ca2+ deficiency over time results in...
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Osteoporosis
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What is the difference between bone modeling and remodeling?
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modeling occurs mostly in children, and osteoblasts and osteoclasts work independently. It is a continuous and prolonged process that reduces after skeletal maturity. Bone Remodeling is when osteoblasts and osteoclasts work in teams, it is life-long and episodic.
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Characteristic features of bone modeling?
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Metaphyseal narrowing, diaphyseal enlargement and drift, flat bone shape
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What cells make up the Basic Multicellular Unit of bone remodeling?
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10 osteoclasts, 100 osteoblasts. The three steps are Activation, Resorption(3 weeks,) and Formation (3 months.) Could have transient osteopenia
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What is the role of hematopoeisis in bones?
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Since the central portion of the bone is inefficient for mechanical work, it is hollow and filled with marrow and contains the mechanism for red and white blood cell formation
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