KIN 3304 1nd Edition Lecture 5 Outline of Last Lecture I. Endochondral Ossification and its 7 StepsII. Nutrient Artery and VeinIII. Metaphyseal Vessels and Periosteal VesselsIV. Neural InnervationV. Regulating Bone GrowthVI. Remodeling of BoneVII. Bone Adaptation to StressVIII. Injury and Repair IX. 4 Steps to Injury RepairX. Aging ProcessOutline of Current Lecture I. Skeletal MuscleII. Neuromuscular Synapse (NMJ)III. Transverse (T) TubulesIV. Myofibrils and MyofilamentsV. Organization of SarcomereVI. Tropomyosin and TroponinVII. Thick FilamentThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VIII. TitinIX. Sliding Filament Theory (SFT)X. Electrical Events at Sarcolemma Surface Cause Muscle ActionXI. End of CycleCurrent LectureI. Skeletal Musclea. Functions of Skeletal Musclei. Produce skeletal movementii. Maintain posture, body positioniii. Support soft tissueiv. Regulate enter and exit materialv. Maintain body temperatureb. Skeletal Movementi. Muscle actions (not contraction) pull on tendons, allow for movementii. Muscles never push only pull1. Think of cranec. Maintain Posture and Body Positioni. Contain muscles that act to maintain posture (postural muscles)ii. Balance…d. Support Soft Tissuei. Abdominal wall, pelvic cavity consists of layers of skeletal muscleii. Protect internal tissues from injuryII. Neuromuscular Synapse (NMJ)a. Skeletal Muscles or voluntary musclesi. Actions can be constantly controlledii. Controlled by nervous systemb. Nerves (bundle of axons) enter the endomysium to innervate individual fibersc. Chemical communication occurs at the neuromuscular synapse (myonerual junction, NMJ)d. Each muscle fiber has 1 synapsei. Usually midpoint of fibere. At the synapse the terminal of neuron is bound to the motor end platef. Shorten = concentricg. Lengthen = eccentricIII. Transverse (T) Tubulesa. Network of tubules that extend into sarcoplasmb. Electrical impulse conducted by the sarcolemma and T tubules stimulate a coordinate..IV. Myofibrils and Myofilamentsa. Sarcoplam contains 100’s-1000/s of myofibrilsb. Each is 1-2 micrometers in diameter: up to 16 inches longc. Myofibrils shorteri. Respond for skeletal muscle actionii. Fibers attach to the sarcoplasm at each end1. Shortens entire cells, give us movementV. Sarcoplasm Reticulma. Each microfibril is surrounded by the SRb. Associated with T Tubules in controlling muscle actionc. On either side of a T Tubule, the SR tubule enlarge, fuse, form chambers (terminal cisternae)i. 2 cisternae + 1 T Tubule = 1 TriadVI. Organization of Sarcomere (KNOW HOW TO LABEL THIS)a. Actin(thin) filaments and myosin(thick) filaments organized in repeating unitsi. This is the sarcomereii. Responsible for fiber muscle actionsiii. The smallest functional unit of muscle fiberb. Each myofibril consists of ~10,000 sarcomeresVII. Thin Filamentsa. Slender protein strand (nebulin) holds F actin strandb. F actin composed of 300-400 globular G actin moleculesc. Each G actin molecule contains an active site that binds to think filamentd. Also contain Tropomyosin and troponinVIII. Tropomyosin and Troponina. Tropomyosin molecule form a chain that covers active sitei. Prevents actin-myosin bindingb. Troponin holds Tropomyosin strand in placec. Troponin must change position, moving Tropomyosin molecules and exposing active sites before muscle action can beginIX. Thick Filamenta. Bundle of myosin moleculesb. ~500 myosin molecules within a thick filamenti. Consists of a double myosin strand with an attached tail and a free globular headc. Oriented away from M linei. Project outward toward surrounding thin filamentii. Known as cross-bridges1. Connect thick and thin filaments during muscle actionX. Titina. Titin at core of each thick filamentXI. Muscle Actiona. Interaction between thick and thin filamentsi. Produces muscle actionii. Called sliding filament theoryb. Initiation requires Ca2+c. Action requires presence of ATPXII. Sliding Filament Theory (SFT)a. Zone of overlap get biggerb. Z line moves closer togetherc. Myosin heads of thick filament bind to active sites on thin filamentsi. Cross-bridge bindingd. Myosin head pivots toward M linei. Pulls thin filaments toward center of sarcomere ii. Cross-bridge cycle detaches, repeatsiii. Thick filament pulls on thin filaments1. Z line moves toward M, sarcomere shortensXIII. Free Ca2+ in Sarcomere Triggers Muscle Actiona. Intracellular [Ca2+] is usually lowi. Ca2+ enter cytoplasm usually pumped into external fluidb. Skeletal Muscle also transport [Ca2+] into terminal cisternae of the SRi. [Ca2+] in cisternae may be up to 40,000 times that of resting fiberXIV. Electrical Events at Sarcolemma Surface Cause Muscle Actiona. Triggers release of Ca2+ from terminal cisternaei. Impulse distributed by T tubules that extend deep into muscle sarcoplasmii. Terminal cisternae becomes permeable to Ca2+b. Ca2+ ions diffuse into zone of overlap i. Bind to troponinii. Troponin changes shape, alters Tropomyosin strandiii. Active sites on actin molecules expandc. Cross-bridge (muscle action) beginsXV. End of Cyclea. Duration depends on electrical stimulationb. Change in Ca2+ permeability is temporaryc. NO impulse:i. SR recaptures Ca2+ii. Troponin-Tropomyosin complex alters active sitesiii. End of cross-bridge