KIN 1223 Unit 4 Lecture 1 How muscles cause movement Physiological process only way muscle can cause movement Myosin cross bridges pull actin causing sarcomere to shorten Develops tension and pulls on bone attachment sites causing movement To cause movement at specific joint Muscle must cross the joint have attachments on either side of joint Movement roles of muscles Role depends on movement situation 1 Agonist Prime Mover a Muscle primarily responsible for causing movement i Biceps Brachii PM for elbow flexion a Opposes particular movement of agonist i Triceps Brachii Antagonist for elbow flexion 2 Antagonist 3 Synergists a Muscles help another muscle i Brachialis Synergist for elbow flexion b Synergy Cooperative action w heavy load some positions i Biceps Brachii Synergist during fast supination or heavy load c Neutralizer type of synergist neutralizes unwanted movement i Triceps Brachii neutralizes elbow flexion so Biceps Brachii can Human body leverage system cause just supination Body functions in movement as a system of levers Bones joints and muscles constitute lever type of simple machine used to gain an advantage in force speed or range system Advantage Able to do less and get more Force advantage Move greater force while applying less force using a simple machine Components of a lever system 1 E Effort force Force you provide with your body by way of your muscles that generate the force to cause movement to occur 2 R Resistance force Force opposing you may be something you are lifting or even weight of the bone segment 3 Fulcrum Distance Moment Arm perpendicular distance from fulcrum to line representing force Torque Force applied to move lever muscle functions Relationship between resistance torque and effort torque will determine how the Torque causes body levers to move Outcome is function of Amount of force Moment arm distance Torque Force x Moment Arm Distance Resistance Torque resistance force at some distance from fulcrum Resistance Torque Resistance Force x Moment Arm Resistance Effort Torque resistance created by muscle pulling on bone to be moved Effort Torque Effort Force x Moment Arm Effort MA longer greater torque MA shorter smaller torque Types of muscle tension When a muscle develops tension between its ends one of three things happens depending on the magnitude of the opposition the resistance torque 1 Muscle tension Resistance Torque a Concentric contraction tension while shortening Isotonic muscle contraction tension i Only way muscle causes movement Prime movers concentric ii LEAST FORCE PRODUCED Least efficient 2 Muscle tension Resistance Torque a Isometric contraction tension without changing length i Important in postural muscle function antagonistic muscle joint stabilization ii Energy not used for shortening 3 Muscle tension Resistance Torque a Eccentric contraction tension while lengthening Isotonic muscle contraction i Muscle acts as a brake to slow or control movement ii GREATEST FORCE PRODUCED 1 Resistance is doing work 2 O2 use lower Classes of Lever Human body levers have a large force DISadvantage Effort and Resistant MA change through ROM 1 First Class Fulcrum between effort and resistance EFR a Advantages determined by length of MA i Effort MA longer Favors Force ii Effort MA shorter Favors speed and range FEW 1st class with this advantage 2 Second Class Resistance between effort and fulcrum ERF a Favors force move large resistance with less effort effort MA always longer than resistance MA b No 2nd class levers in body 3 Third Class Effort between fulcrum and resistance FER a Favors speed and range effort moves through less distance and at slower speed than resistance Effort MA always shorter than resistance MA b Force Disadvantage c Most in humans are 3rd class Muscle Lab Setting Muscle twitch response to single brief threshold stimulus Some muscles have very rapid twitch times some longer and slower Three phases 1 Latent Period time from stimulation to start of contraction a Ca 2 released troponin moves tropomyosin cross bridges attach etc 2 Period of Contraction time from onset of contraction to peak tension a Actin is being pulled by myosin 3 Period of Relaxation No force generated a Cross bridges release b Ca 2 pump working Graded Contraction Single muscle twitch lab phenomenon Graded muscle responses variations degree of muscle contraction 1 Frequency of stimulus a 2 stimuli in rapid succession Wave Summation i Strength of 2nd twitch 1st twitch 2nd starts from partly contracted muscle left over Ca2 b Increasing stimulation rate shorter relaxation time i Summation becomes greater Eventually no indication of c Tetanus smooth sustained contraction allowing for controlled relaxation phase movements i Most voluntary muscle contractions are short term tetanic contractions 2 Strength of stimulus a Stronger stimulus recruits more motor units Multiple Motor Unit Summation or Recruitment Increases number of muscle fibers involved i ii Stronger contraction b Treppe staircase effect stimuli too far apart to cause wave summation i Each resulting contraction is stronger ii Increased Ca2 heat responsible for increasingly stronger contractions iii Basis for warm up activities Muscle Tone partial contraction Muscles exhibit slight contractions at all times Posture Ready to respond to stimulation Smooth Muscle Differences between smooth and skeletal muscle 1 Structural a Smooth muscle fibers shorter and thinner b Single central nucleus c Only thin Endomysium d No T Tubules Has caveolae tiny invaginations of the sarcolemma 1 Keep Ca2 close to sarcolemma 2 Ready to trigger contraction 3 Poorly developed SR e Actin Myosin differences Very thin Randomly arranged no striations appear spiral along fiber 1 No sarcomeres Actin to Myosin ratio 13 1 Myosin cross bridges along entire length Actin only has tropomyosin no troponin Actin anchored by dense bands along sarcolemma between Intermediate filaments attached to dense bodies caveoli 1 Dense bands correspond to Z discs Movement results when myosin pulls actin 2 Functional a Ca 2 from SR diffusion from extracellular fluid Ca 2 interacts with protein Calmodulin a Kinase enzyme on myosin head Initiates smooth muscle contraction process 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 Smooth muscle contraction Slow sustained contractions Little energy expenditure fatigue resistant More energy