KIN 3304 1nd Edition Lecture 5 Outline of Last Lecture I Endochondral Ossification and its 7 Steps II Nutrient Artery and Vein III Metaphyseal Vessels and Periosteal Vessels IV Neural Innervation V Regulating Bone Growth VI Remodeling of Bone VII Bone Adaptation to Stress VIII Injury and Repair IX 4 Steps to Injury Repair X Aging Process Outline of Current Lecture I Skeletal Muscle II Neuromuscular Synapse NMJ III Transverse T Tubules IV Myofibrils and Myofilaments V Organization of Sarcomere VI Tropomyosin and Troponin VII Thick Filament These 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 Titin IX Sliding Filament Theory SFT X Electrical Events at Sarcolemma Surface Cause Muscle Action XI End of Cycle Current Lecture I Skeletal Muscle a Functions of Skeletal Muscle i Produce skeletal movement ii Maintain posture body position iii Support soft tissue iv Regulate enter and exit material v Maintain body temperature b Skeletal Movement i Muscle actions not contraction pull on tendons allow for movement ii Muscles never push only pull 1 Think of crane c Maintain Posture and Body Position i Contain muscles that act to maintain posture postural muscles ii Balance d Support Soft Tissue i Abdominal wall pelvic cavity consists of layers of skeletal muscle ii Protect internal tissues from injury II Neuromuscular Synapse NMJ a Skeletal Muscles or voluntary muscles i Actions can be constantly controlled ii Controlled by nervous system b Nerves bundle of axons enter the endomysium to innervate individual fibers c Chemical communication occurs at the neuromuscular synapse myonerual junction NMJ d Each muscle fiber has 1 synapse i Usually midpoint of fiber e At the synapse the terminal of neuron is bound to the motor end plate f Shorten concentric g Lengthen eccentric III Transverse T Tubules a Network of tubules that extend into sarcoplasm b Electrical impulse conducted by the sarcolemma and T tubules stimulate a coordinate IV Myofibrils and Myofilaments a Sarcoplam contains 100 s 1000 s of myofibrils b Each is 1 2 micrometers in diameter up to 16 inches long c Myofibrils shorter i Respond for skeletal muscle action ii Fibers attach to the sarcoplasm at each end 1 Shortens entire cells give us movement V Sarcoplasm Reticulm a Each microfibril is surrounded by the SR b Associated with T Tubules in controlling muscle action c On either side of a T Tubule the SR tubule enlarge fuse form chambers terminal cisternae i 2 cisternae 1 T Tubule 1 Triad VI Organization of Sarcomere KNOW HOW TO LABEL THIS a Actin thin filaments and myosin thick filaments organized in repeating units i This is the sarcomere ii Responsible for fiber muscle actions iii The smallest functional unit of muscle fiber b Each myofibril consists of 10 000 sarcomeres VII Thin Filaments a Slender protein strand nebulin holds F actin strand b F actin composed of 300 400 globular G actin molecules c Each G actin molecule contains an active site that binds to think filament d Also contain Tropomyosin and troponin VIII Tropomyosin and Troponin a Tropomyosin molecule form a chain that covers active site i Prevents actin myosin binding b Troponin holds Tropomyosin strand in place c Troponin must change position moving Tropomyosin molecules and exposing active sites before muscle action can begin IX Thick Filament a Bundle of myosin molecules b 500 myosin molecules within a thick filament i Consists of a double myosin strand with an attached tail and a free globular head c Oriented away from M line i Project outward toward surrounding thin filament ii Known as cross bridges 1 Connect thick and thin filaments during muscle action X Titin a Titin at core of each thick filament XI Muscle Action a Interaction between thick and thin filaments i Produces muscle action ii Called sliding filament theory b Initiation requires Ca2 c Action requires presence of ATP XII Sliding Filament Theory SFT a Zone of overlap get bigger b Z line moves closer together c Myosin heads of thick filament bind to active sites on thin filaments i Cross bridge binding d Myosin head pivots toward M line i Pulls thin filaments toward center of sarcomere ii Cross bridge cycle detaches repeats iii Thick filament pulls on thin filaments 1 Z line moves toward M sarcomere shortens XIII Free Ca2 in Sarcomere Triggers Muscle Action a Intracellular Ca2 is usually low i Ca2 enter cytoplasm usually pumped into external fluid b Skeletal Muscle also transport Ca2 into terminal cisternae of the SR i Ca2 in cisternae may be up to 40 000 times that of resting fiber XIV Electrical Events at Sarcolemma Surface Cause Muscle Action a Triggers release of Ca2 from terminal cisternae i Impulse distributed by T tubules that extend deep into muscle sarcoplasm ii Terminal cisternae becomes permeable to Ca2 b Ca2 ions diffuse into zone of overlap i Bind to troponin ii Troponin changes shape alters Tropomyosin strand iii Active sites on actin molecules expand c Cross bridge muscle action begins XV End of Cycle a Duration depends on electrical stimulation b Change in Ca2 permeability is temporary c NO impulse i SR recaptures Ca2 ii Troponin Tropomyosin complex alters active sites iii End of cross bridge cycle