Sarcomere (Actin-actin)Actin and MyosinHow muscle contraction works?AP crosses the motor endplate to the muscle, releases Calcium, Calcium diffuses through the muscle, causes the sites of actin filaments to open up.on myosin filaments, there are like fingers (myosin heads) that are sensitive to the actin filament binding sitesif binding sites open, fingers reach out and grab on. then flexactin filament is being pulled across the myosin filamentthese filaments slide on top of each other => slide filament theorySliding filament theoryMAP stimulates release of calciumresults in uncovering of actin ATP binding sitesswinging myosin cross-bridges (heads) engage binding sitesflex to pull actin filaments towards center of sarcomere (i.e., thick and thin filaments “slide” over one another)not shortening every sarcomere in the entire muscle“single motor unit”Force generationwhen muscle contracts, contractile components shorten while elastic portion stretchesif muscle tendon held rigid, tension built up (isometric contraction ) – no movement <> isotonic (movement)if released, muscle shortens and external load movedshorten the sarcomere, but not actually moving the structureIsometric contractionbuilding up tension in muscle-> sarcomeres are contracting, stretching elastic components.Isotonic shorteningIf released, allowing sarcomeres to fully shorten, then the load gets to moveIf you are trying to lift weights, you are building up tensions (creating force), but not enough force to be able to move the loadForce generationnumber of ways to build up forcefiring ratehow many AP’s and subsequent contractions or twitches take placetwitch generated by each MAP (every MAP will create muscle twitch = muscle contraction)increase firing rateif I speed up AP before another twitch happens, they build on one another so that I can increase the force generated by musclesrecruitmenthow many other motor units involvedantagonist<>agnosist?at the simplest level, I can stimulate one motor unit onlybut if I need to move sth faster/heavier, it needs more motor unitsmore motor units, more force=>this is within a musclein a case where multiple muscles acting on the same jointagonist muscle (2 diff muscles that work in the same direction )antagonist (opposite direction)we can build up force within a muscle / or around the jointForce generation principles**how much overlap do I have between the thick and thin filaments100= optimal resting length of the sarcomere<100, sarcomeres being shortened before it do anything>100, stretch outsarcomere length vs. Tensionresting length of sarcomere importantat 100, able to obtain maximal overlap of thick and thin filaments on contractioncan generate the maximal force because I have maximal overlapat >100%, reduced initial overlap, with fewer cross-bridges and less maximal tensionat <100%, excessive initial overlap and less maximal tensionForce generation principlesforce versus velocitygreater applied loads require greater muscle forcegreater applied loads associated with slower speed of contractionMeasuring muscle activityintracellular –hooked wire electrodeinto the cell/musclerecord electrical activity in the muscleextracellular –surface electrodeelectrical activity of muscles in the windowdifference between the two : surface EMG -> less interference patternElectromyographic signalsA- single motor unit potentialssingle wavecan get from hooked wire electrodeB- rapid sequence of spikesmultiple single motor units firing at different ratesC- single motor unit spikes and interference pattern resulting from the superimposition of many random spikesmultiple single motor units firing at different rateswhich one is better?finest level of control of muscles => Abroad picture of muscles -> CSignal conditioningwant to know how active the muscle is ..Rectificationtake absolute value of each data pointmakes all negative values positiveSmoothingaverage waveform over given time windowget envelope of EMG activitybigger window -> more smoothinggreater smoothing -> less the detailEMG examplelevatorveli palatine activity raises soft palatenotice activity prior to A associated with /a/notice decrease in activity at A associated with /n/peak activity between A and B associated with /s/delay between when the muscle action happens and the movement associated with that musclebecause muscle has to contract and causes the structure to move (mechanical)all these sounds (except /n/) are oral soundssoft palate has to be closed for the oral soundswhy there are different bursts? (some have higher oral pressure, lower oral pressureburst = sounds with higher oral pressurewhen the pressure is high, soft palate has to be closed tightly enough so that the increased pressure does not go up to the nasal cavitymotor control system has to know what kind of pressures happen in the oral cavitycompetition from other musclessoft palate is connected to the tongue by musclesas the tongue moves up and down, connection between the tongue and the soft palate movestongue down, palate elevationCSD 3112 1st Edition Lecture 5Outline of Last Lecture I. Nervous system subdivisionsII. Motor Neurona. Neural transmissionb. Synapsec. Action Potentiald. Myelin SheathIII. Motor systemsa. Termsb. Muscle architectureOutline of Current Lecture I. Sliding Filament TheoryII. Force Generationa. Tensionb. PrinciplesIII. Muscle Activitya. Electromyographic signalsb. Signal conditioningCurrent LectureSarcomere (Actin-actin)Actin and MyosinThese 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.How muscle contraction works?- AP crosses the motor endplate to the muscle, releases Calcium, Calcium diffuses through the muscle, causes the sites of actin filaments to open up.- on myosin filaments, there are like fingers (myosin heads) that are sensitive to the actin filament binding sites- if binding sites open, fingers reach out and grab on. then flex- actin filament is being pulled across the myosin filament- these filaments slide on top of each other => slide filament theory Sliding filament theory- MAP stimulates release of calcium- results in uncovering of actin ATP binding sites- swinging myosin cross-bridges (heads) engage binding sites- flex to pull actin filaments towards center of sarcomere (i.e., thick and thinfilaments “slide” over one another)  not shortening every sarcomere in the entire