Tissue Composition, Proteins, Muscle Structure Study Notes

#separator:tab #html:true what are 5 desirable attributes of tissue composition?- ability to produce force in a controlled manner - elasticity - reponsive to training - able to repair following damage - metabolic flexability how many genes are in the human genome?~21,000 genes "the amount of a given protein present in a cell is a result of [...]""the amount of a given protein present in a cell is a result of multiple levels of control - transcription, translation, post-transitional-modifications, and rate of degradation" how does oxygen affect amino acid and protein structure?- O2 has a higher affinity for electrons than carbon and therefor won't share the electrons equally (will be slightly more negative) what is a hydrogen bond?- occurs  when a hydrogen from an OH group is slightly positive and attracted to a slightly negative oxygen from another molecule why are non-polar amino acids attracted by default?- non polar amino acids are hydrophobic - they are repelled from the water in the ECF and cluster together what are ionic bonds?- positive molecules being attracted to negative molecules what are 4 functions of proteins?- structual components in cells and the body - molecular motors (myosin) - catalyze reactions between molecules (enzymes) - communcation - can be hormones, receptors, and signalling relays "protein functions is sensitive to [...], and the [...]""protein functions is sensitive to temperature, pH, and the prescense/absense of chemicals " how does phosphate regulate protein function?- phosphorylation via a kinase enzyme causes subtle changes in protein configuration - often swiches between the proteins on and off modes what is the order of muscle connective tissue from superficial to deep?- epimysium - perimysium - endomysium - basement membane what is the epimysium?- a sheath surround entire muscle - fuses with tendon - separates muscle groups from eachother - protective layer that absorbs force what is the perimysium?- divides the muscles into fascicles - blood vessels and nerves are found in gaps between fascicles what is endomysium?- surrounds each muscles fibre - capillaries are found in between fibres - transmits force "[...] is the most expressed protein in the body""collagen is the most expressed protein in the body - collagen and elastin are the strcutua proteins" what is the sacrolemma?- composed of plasmalemma and basement membrane - considered the outermost layer of each muscle fibre - meshes together with connective tissue in between muscle fibres  "the basement membrane has gluscose/sugar which makes it [...]""the basement membrane has gluscose/sugar which makes it sticky " what are the basal lamina and reticular lamina?- basal lamina is te internal fibre facing layer of the basement membrane (faces plasmalemma) - reticular lamina is the external and endomysium layer - reticualar lamina fibres are more loosely arranged  which will rupture first? the muscle fibre or the basement membrane?muscle fiber what are four functions of the basement membrane?- scaffolding for muscle cells to grow along/within - connects muslces cells to the endomysium - terminates muscle contraction via acetylchoinesterase (chops up acetylcholine) - attract motor neurons to form a neuromuscular junction what major types of membrane-embedded proteins are found in the plasmalemma?- inegrins and dystroglycan complex proteins (ankor points linking the protein networks inside the muscle cell to the basal lamina) - hormone receptors - kinases - channels and transport systems what is the primary function of the SR (sarcoplasmic reticulum)?store Ca2+ ions where are myonuclei dispersed?- inner surface of plasmalemma what is the difference between myonuclei and satellite cells?satellite cells are under the basement membrane but outside the plasmalemma. myonuclei are under the basement membrane and plasmalemma "mitochondria are [...] organelles. they [...] - they aren't rigid.""mitochondria are dynamic, branched organelles. they fuse and divide - they aren't rigid. " what are the 2 pools of mitochondria?- subsarcolemmal (SS): found near the edge of the sarcolemma - intermyobfibrillar (IMF): found in between myofibrils; usually lined up with z-disks) what is tropomysoin?- helps provide structure to thin filaments and blocks/regualtes myosin interactions with the help of troponin what is titin?- the largest protein (wighs >4000 kDa) - spans from the z-disk to the m-line, holding it together - limits the ROM of sarcomeres an provides resting tension in muscles what is SDS-PAGE and what is it used for?- biochemical analysis use to determine protein size - muslce biopsy is homogenized and then put into gell - electric field is applied to the gell which pushes the proteins through the gell  - smaller proteins make their way through the gell easier and larger ones get stuck - protiens of known sizes are used as a control sample  "titin [...] as muslce fibres are stretched out""titin uncoils as muslce fibres are stretched out " what is the significance of titin being stretched out?- helps turn on signalling pathways - the more you build muslce the more it is in a  stretched/elongated state where it exposes/turn on signalling pathways for all these kinases what are nebulin and plectin?- nebulin is a large protein that acts as scaffold for actin to assemble on - plectin lines the outside of the myofibril what are costameres?- complex of proteins (dystyoglycan complex + integrins) that help connect the inside of the muscle fibre to the outside - transmits force - at every z-disk for force transfer what is FAK?focal adhesion kinase - turns on when integrins are subject to high tension - phsophorylates several protein targets, turning them on which is important for muscle growth and hypertrophy what is the MTJ?myotendinous junction - where the muscle fibres attatch to the tendon - transmits most of the force produced by the fibre - sarcolemma invagination and tendon ECM integrate - thin filaments at the terminal end connect with integrins and dystroglycan complexes which span the plasmalemma and attach to the BM what is the most common site of injury/tear?-MTJ - high force and tension is developed here what are congenital myopathies?- group of muscle disorders - mostly result from defective structual or accessory proteins what are muscular dystrophies?- defect in the protein dystrophin - linked to the x chromosome (affects 1 in 3500 males) - leads to death in late adolescence or early adulthood (effects ALL muscles) - muscles become weak and eventually breakdown (constant cycle of damage --> regeneration which eventually leads tot depletion of satellite cells) - chornic inflammation contributes to overzeloous fibre breakdown and ECM protein expression what are the two major elements that make up connective tissue?1. ECM: made up of protein liek collagen and other stuff (ground substance) 2. Cells such as fibroblasts "CT has good blood supply amd innervation however, [...] do not""CT has good blood supply amd innervation however, tendons, ligamnets and cartilage do not " "endomysium is [...]""endomysium is irregular " "perimysium and epimysium are [...]""perimysium and epimysium are regular " "all CT layers surrounding SK muscle are [...]""all CT layers surrounding SK muscle are dense " what collagens are found in each layer of connective tissue surrounding muscles?1. epimysium- fibrillar collagen 2. perimysium- fibrillar collagen 3. endomysium- fibrillar collagen, collagen IV and VI epimysium, perimysium, and endomysium are all distinct compartments. T or F?F - they all run into eachother  "Tendon CT handles the highest force load and is [...]""Tendon CT handles the highest force load and is dense and regular - it is the best at trasnmitting force" which collagen types play the most important role in tendon and muscle?- COllagen I and IV how is collagen synthesized?1. single protein chain (collagen \(\alpha\)-chain) is made and must be hydroxylated which requires vitamin c 2. 3 chains wrap around eachother to form a triple helix (procollagen) 3. non-helical ends are cleaved off by procollagen terminus proteinase to form a cleaner tropocollagen what health issue is caused by defects in procollagen terminus proteinase?- ethers-danlose syndrome - collagen doesn't pack up tightly together and the CT is loose as a result why are glycine, proline, and lysine the most common amino acids in collagen?- glycine is very small and allows chain flexibility - proline and lysine have large side chains which forces helical arrangement of the 3 collagen fibres - side chains are targeted to be hydroxylated by enzymes - alpha-ketoglutarate hydroxylates proline and lysine using Fe2+ as an essential cofactor why is vitamin c important for collagen synthesis?- recylces the used Fe3+ ions back into usable Fe2+ - Fe2+ is a cofactor for proline hydroxilation why is proline hydrozylation important in collagen synthesis?- makes the side tails slightly more electronegative so they are attracted to the other collagen fibres (promote tripical helixal shape) what enzyme ties the ends of the tropocollagen molecules to its neighbour?- lysyloxydase what are the roles of the different types of collagens and which ones are fibrillar?1. type I: smoothest and thickest fibres, great tensile strength - fibrilar 2. type III and V: found in various forms in the mysiums, good tensile strength, not as thick and occasioanlly branch - fibrilar 3. type IV: transmits force moderately in all directions, forms a mesh - non fibrilar what are 3 components to flexibility?1. pliability of ECM  2. myofibril length via sarcomere number 3. sensory and neuromuscular feedback (first thing that improves) what can have impacts on collagen flexibility?1. cross-linking between collagen fibres occurs as you age: increases stability but decreases flexibility 2. the amount and type of collagen fibres- more collagen with a variation of types is less flexible 3. density- larger fibril sizes along with them being closer together is less flexible 4. orientation- the straighter and more regular the collagen fibres, the less flexible they are "the more elastic something is, the [...] it is to rupture but the [...] force it produces""the more elastic something is, the less likely it is to rupture but the less force it produces trade off between force and flexibility" why do people with diabetes experience more cross-linking of collagen fibrils?- increased blood glucose increases the chance of glycation whcih can react with collagen what does proxyl hydroxylase do?- using Fe2+ as a cofactor, it converts alpha-ketoglutarate to succinate (same as krebs) and proline to hydroxyproline which uses one O2 and producing one CO2 - important reaction when forming the triple helix structure of a collagen fibre what does lysyl hydrozylase do?same as prolyl hydroxylase but it acts on lysine what does lysyl oxidase do?- ties the ends of tropocollagen molecules to its neighbors to form a fibril what is the difference between a collagen fibril and fibre?- collagen fibrils are a collection of tropocollagen tied together by lysyl oxidase - collagen are a bunch of collagen fibrils lined up together, following lines of tension is cross-sectional area important in force distribution? which part muscle/tendon has the highest point of stress?- a higher cross-sectional area allows the force to be distributed over more space (less total stress) - thinnest areas have the most stress (tendon point of insertion) what is the formula for stress?stress = force/area what is the most common protein found in tendons?- collagen type I what is the difference between tendon and skeletal muscle concentration?- skeletal muscle is 75% water and 20% protein - tendon is 60% water, 39% protein, and 1% ground substance what is the organization of tendons from super fiscial to deep?1. tendon/eptenon 2. endotenon 3. collagen fascicles 4. collagen subfascicles 5. collagen fibers 6. tropocollagen what part of the tendon transmits force?- the primary fiber bundle (collagen susbfascicles) what is the difference between endotendon and the mysiums?- little force transduction - its a passage zone for small blood vessels, capillaries, and neurons what is the role of epitenon?- transmits some force and protects the tendon from outside trauma what is the role of paratenon?- loose protective layer that handles friction with neighbouring tissues - sometimes there is a proper synovial lining that secrete synovial fluid what is the difference between the achilles tendon and other tendons?- the collagen fibres sprial along the length of the tendon - because it has to deal with a lot of force (every step, etc.) what cell is responsible for maintaining, improving, and/or repairing CT?- fibroblasts: - they express, secrete and fit collagen into existing ECM where are fibroblasts found in tendon?- lined up between primary collagen fibre bundles where are fibroblasts found in muscle?- in between muscle fibres (less frequently than tendon) what is the skeleton of a fibroblast made of?- actin and myosin filaments to contract and produce force - focal adhesions which are analogous to costameres of skeletal muscles: they anchor the stress fibers to the CT what extracellular signals cause fibroblasts to express collagen?- tension via inegrins and FAK - growth factors what is the role of integrins?- relay information outside to in "tension stimulates [...] and more [...] collagen expression""tension stimulates more collagen expression and more organized collagen expression " where does the fibroblast produced collagen?- collagen \(\alpha \)-chains are produced in the rough ER and hydroxylation of lysine and proline occurs here to form procollagen - procollagen is secreted (via vessicles) and cleaved into tropocollagen which is incorporated into growing fibrils in the ECM why do you want to exercise during injury recovery?- proved tension - straightens collagen fibrils while new tropocollagen is incorporated - straightens fibres while fibrils are incorporated do fibroblasts produce tension?yes, they organize the ECM by pulling on collagen fibres - fibroblasts are connected via gap junctions to coordinate their contraction efforts - they line up and pull together: gap junctions allow communication between fibroblasts why does exercise initiate adaptation and render tissue more resistant to damage and organization?- when the damage caused by exercise is repaired, it is prepared better for next time (exact mechanisms are unknown) what are three possible mechanisms of connective tissue adaptation to exercise?1. increased collagen density 2. more type I collagen composing the ECM 3. increased fibroblast number and activity level what could be measured in ECF as an indicator of the rate of collagen synthesis?- tropocollage levels - terminal pro-peptides (the loose ends cleaved off procollagen) what were the results of the study that measured changes to type I collagen turnover following acute and chronic exercise?- collagen synthesis was turned down immediatly after exercise but there was a large increase 72 hours later - after prolonged training, collagen synthesis increased dramatically after 4 weeks  (1-3 months) "[...] training causes a large increase in collagen synthesis""resistance training causes a large increase in collagen synthesis " what do changes in collagen synthesis contribute to?- increased collagen synthesis leads to increase in tendon size/tendon hypertrophy and increased ability to handle tension (less deformation per load) "exercise trained mice have a [...] tendon size and more tendon [...]""exercise trained mice have a greater tendon size and more tendon fibroblasts - fibroblasts from trained mice also had a more contractile phenotype and produced more type I collagen as well as more dense stress fibres" does a thicker/denser tendon have any impact on exercise performance?yes: - increased torque and force production - reduced strain - increased tendon stiffness - reduced VO2 at set running speeds "incidence of tendon rupture is high in [...] users comared to similar non-user athletes. why?""incidence of tendon rupture is high in anabolic steroid users comared to similar non-user athletes. why? - fibroblasts will secrete more collagen and thicken tendons in someone who used steroids but they will be more disorganized with calcified deposits between fibrils - elasticity of tendons is reduced to the point of fragility (stress levels get too high)" what are 6 functions of bone and the skeletal system?1. support framework for soft tissue 2. protection 3. movement 4. mineral homeostasis (especially calcium) 5. blood cell production (hematopoiesis) 6. fat strorage (triglycerides) where is red bone marrow found?- spongy bone (site of blood cell production) what are condrocytes, osteoblasts, osteocytes, and osteoclasts?- ocndocytes create the original cartilage blueprint for bone and is responsible for growth at epiphyseal plates - osteoblasts line periosteum and endosteum and secrete collagen and bone mineral apatite - osteocytes are mature osteoblasts trapped between lamellae, they help regulate metabolism, nutrients, and wastes within the bone - osteoclasts are large multinucleated cells that are concentrated in the endosteum and found throughout trabeculae, dissolve bone mineral and collagen what is bone mineral apatite?- gives bone its rigity and gets laid into the collagen of bones - fit into little spaces between fibers what do condrocytes secrete into the gaps of bones during development?- apatite "stiff bones [...] the chance of fracture if they're overloaded""stiff bones increases the chance of fracture if they're overloaded - less mineralization means more bone flexibility" what causes longitudinal growth in bones?- chondrocytes expanding the chartilate ECM at the epiphyseal plate what is cartilage composed of?- heterofibrils of type II, IX-XI collagen what is proper bone ECM made of and what is it called when it begins to replace cartilage at the epiphyseal plate?- collagen types I and V - endochondral ossification how does bone growth in diameter occur?- due to periosteal osteoblasts - lay down new material and expand outwards - the bone eventually encapsulates blood vessels which is how bone gets materal and osteon shape is formed what is the difference in bone growth between sexes?- similar before puberty - during puberity, female bones grow thicker compact bone but do not expand outwardly as much as males' - both female and male bones expand on the outer circumferance but female medullary cavity does not (males does) and it may even get smaller - during aging, female bones lose more inner compact bone what hromones are bone cells sensitive to?- insulin, insulin-like growth factor, thyroid hormones, PTH, testosterone, mestrogen, progesterone what nutritional deficiencies are related to less bone growth during puberty?- Ca2+, phosphorus, other minerals - vitamin D, K, A, C - protein, energy (calories) what cells are involved in bone remodelling?- osteoblasts, osteoclasts, and osteocytes how are osteoblasts similar to fibroblasts?- sensitive to tension in the surrounding ECM collagen - they communicate with neighboring osteocytes through gap junctions when they sense tension to tell them to further lay down bone how is hydrogen ivolved in bone remodelling?- makes bone mineral apatite fall apart what are matrix metalloproteinases?- secreted to digest bone collagen by snipping collagen fibers what does PTH (parathyroid hormone) do?- released during periods of low blood Ca2+ - stimulates osteoclasts and inhibits osteoblasts (breaks down more bone) how do estrogen and testosterone affect bone reabsorption?- they slow it down and stimulate bone formation why are osteoclasts multinucleated?- a type of monocyte derived from HSC become fused together from a signal called RANKL found in osteoblasts why do osteoblasts signal for remodelling?- to maintain a balance between remodelling and breakdown - as osteoblasts becomes more numerous, RANKL is signalled how does estrogen affect long terem bone remodelling?"- limits the expression of RANK in osteoblasts - stimulates local cells to express a ""decoy"" RANK protein called OPG (osteoprotegerin) - OPG binds to RANKL which inhibits RANK from binding so HSC-monocyte activation cannot occur" "lack of estrogen leads to [...]""lack of estrogen leads to bone loss " "bone anabloic processes are increased by [...] so more [...] leads to [...] which eventually leads to mineralization""bone anabloic processes are increased by tension so more tension leads to more collagen which eventually leads to mineralization " what are the four zones of the OTJ (osteotendinous junction)?1. tendon: mostly type I collagen fibres with fibroblasts found in between 2. fibrocartilage: type I and II collagen (not as good at transmitting force) and chondrocytes emerge with fibroblasts being less numerous 3. mineralized fibrocartilage: mostly type II collagen with chondrocytes producing apatite crystal  4. bone: osteoblasts and osterocytes appear; type I collagen; sharpey's fibres (reaally big type I collagen that anchors the base of mineralized fibrocartilage to bone) pentrate periosteum and embed in the bone ECM how does bone respond to exercise?- it adapts to become better at handling forces - impact training is the best stimulus for increased BMD but training cannot overcome nutritional or hormonal deficiencies what is osteoporosis?- when bone mass is 2.5 SD lower tha npopulation norms - can happen when inactive people fo not prove stress-activation of collagen synthesis and bone mineraliation as wel can when men and women get older so testosterone and estrogen levels drop off (very problematic in post-menopaual women) what is stress-shielding?- weight bearing stress normally transmitter through bone is reduced (when prothesis are used) - results in further bone damage beacuse the neghboring bones are not getting the force that promotes osterblast activity what are the 3 stages of recovery?1. inflammatory phase: - neutrophils and macrophages phagocytose debris and trim damaged proteins 2. reparative phase: - new tissue is formed by fibroblasts, osteoblasts, chondrocytes, satellite cells, etc. 3. remodelling phase: - new tissue is not the same as original and needs to be re organzied - will never be teh same as original and age effects its ability to remodel what do mesenchymal cells do?- produce osteoblasts, osteocytes, chondrocytes, fibroblasts, and adipocytes what is bridge-enhanced ACL repair?- bovine tissue ECM (10 mL of patient blood in it; blood contains stem cells and growth factors that can accelerate healing) is inserted as a scaffold for the ACL - resulated in higher hamstring strength than the standard group

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