Anatomy and Physiology 1 Unit 4 Lecture 1 I Muscle Movement a Muscles contract cross bridge pull actin and the sarcomere shortens and pulls the attachment site of the bone b The muscle must cross the joint to cause movement in the joint c Agonist prime mover responsible for causing movement Quadriceps for d Antagonist oppose prime over ex triceps extension to biceps flexion e Synergist assist the prime mover ex biceps during fast or heavy hip flexion supination i Also neutralize unwanted movement ex neutralizes flexion of bicep II Leverage System able to do less and get more during supination III Muscle contractions a Effort muscle pull b Resistance object and opposition c Fulcrum middle d Moment arm perpendicular distance from fulcrum to line representing e Torque force that is applies to move the lever force moment arm force distance torque i As the moment arm changes the torque will change ex bicep curl ii Causes body levers to move iii Resistance torque and effort torque a b Isometric contraction tension developed without changing length ex postural muscles antagonist muscles joint stability i Tension resistance torque Isotonic contraction muscle produce s same amount of tension throughout ROM i Concentric tension while shortening muscle tension is greater than resistance torque prime movers ii Eccentric tension while lengthening resistance torque muscle torque muscle acts as a break letting down from a pull up c If the amount of ENERGY USED is the same i Eccentric greatest force produced resistance doing work low O2 use Isometric energy not used for shortening ii iii Concentric least efficient least force produced energy used for shortening not available for producing tension IV Lever Classes a First class fulcrum between effort and resistance If effort MA longer force is favored i ii Effort MA shorter favors speed and range b Second Class resistance between effort and resistances but FAVORS FORCE NONE IN human body i Move large resistance with less effort effort movement arm MA longer than resistance MA c Third Class favors speed and range most human body levers i Effort moves trough less distance and at slower speed than resistance ii Force MA shorten than resistance MA iii Force disadvantage V Muscle twitch response to single brief threshold stimulation a Latent period time of stimulation to start of contraction Ca2 released troponin moves tropomyosin ect b Contraction period time from onset of contraction to peak tension i Actin being pulled by myosin c Relaxation period no force generated i Cross bridge released and Ca2 pump working d Graded contraction of single muscle twitch i Frequency 2 stimuli in rapid succession 1 Second twitch stronger than 1st Called wave summation 2 Increasing stimulation rate shorter relaxion time and summation becomes greater 3 Eventually no indiction of relation phase 4 Tetanu s fused into smooth sustained contraction most voluntary muscle contraction are short term tetanic contractions a Smooth sustained contractions smooth movements ii Strength of stimulus stronger stimulus recruits more motor units 1 Increases number of muscle fibers involved a Stronger contraction called multiple motor unit b Treppe summations or Recruitment that results with each contraction being stronger stimuli too far apart to cause wave stimulation i Staircase effect VI Muscle Tone continual partial contraction ex Posture ready to respond to stimulation a Smooth muscle shorter thinner fibers No T tubules i Has caveolae tiny invaginations of the sarcolemma keep Ca2 close to sarcolemma ready to trigger contraction poorly developed SR ii Has actin and myosin in thin randomly arranged order no striations 1 Higher actin to myosin ratio 13 1 2 Myosin cross bridges along entire length 3 Actin no troponin anchored by dense bands along sarcolemma between caveoli correspond to Z discs 4 No sarcomeres 5 Functional differences Ca from SR and diffusion from extracellular fluid a Ca interacts with protein Calmodulin and a kinase enzyme on myosin head initiates contraction process iii Steps in smooth muscle contractions 1 Ca 2 binds to calmodulin activates it 2 Calmodulin activates kinase enzyme 3 Kinase enzyme catalyzes ATP for energy 4 Actin and Myosin interact contraction iv More energy efficient then skeletal muscle v Stress relaxation response skeletal muscle contracts more forcefully when stretched 1 smooth muscle contracts when stretched then relaxed vi Generates large amount of tension vii Neurotransmitter prevents contraction NT excitatory contracts muscle inhibitory for skeletal muscle always excitatory 1 NT 2 Smooth muscle responds to several chemicals stimulated by autonomic NS
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