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AP Biology Animal Locomotion What are the advantages of locomotion? Muscles & Motor Locomotion sessile motile Why Do We Need All That ATP? AP Biology Lots of ways to get around… AP Biology Lots of ways to get around… mollusk mammal bird reptile AP Biology AP Biology 1 AP Biology Lots of ways to get around… Muscle bird arthropod mammal bird involuntary, striated auto-rhythmic voluntary, striated heart moves bone multi-nucleated AP Biology AP Biology Organization of Skeletal muscle evolved first involuntary, non-striated digestive system arteries, veins Human endoskeleton skeletal muscle plasma membrane nuclei tendon 206 bones muscle fiber (cell) AP Biology myofibrils myofilaments AP Biology 2 AP Biology Muscles movement Muscles do work by contracting skeletal muscles come in antagonistic pairs contracting = shortening tendons ligaments flexor vs. extensor move skeletal parts connect bone to muscle connect bone to bone AP Biology Structure of striated skeletal muscle AP Biology Muscle filaments & Sarcomere Muscle Fiber muscle cell divided into sections = sarcomeres Sarcomere Interacting proteins functional unit of muscle contraction t ti alternating bands of thin (actin) & thick (myosin) protein filaments braided strands actin tropomyosin troponin AP Biology thin filaments AP Biology thick filaments myosin 3 AP Biology Thin filaments: actin Complex of proteins braid of actin molecules & tropomyosin fibers Thick filaments: myosin Single protein AP Biology Thick & thin filaments Myosin tails aligned together & heads pointed away from center of sarcomere myosin molecule long protein with globular head tropomyosin fibers secured with troponin molecules bundle of myosin proteins: globular AP Biology heads aligned Interaction of thick & thin filaments Cross bridges connections formed between myosin heads (thick filaments) & actin (thin filaments) cause the muscle to shorten ((contract)) sarcomere AP Biology AP Biology sarcomere 4 AP Biology Where is ATP needed? Closer look at muscle cell binding site Sarcoplasmic reticulum thin filament (actin) myosin head ADP 12 thick filament (myosin) ATP So that’s where those 10,000,000 ATPs go! Well, not all of it! form cross bridge 11 1 3 release cross bridge Cleaving ATP → ADP allows myosin1 AP Biology head to bind to actin filament Transverse tubules (T-tubules) shorten sarcomere 4 Mitochondrion AP Biology multi-nucleated Ca2+ ATPase of SR Muscle cell organelles Muscle at rest Sarcoplasm Interacting proteins muscle cell cytoplasm contains many mitochondria Sarcoplasmic reticulum (SR) There’s the rest of the ATPs! at rest, troponin molecules hold tropomyosin fibers so that they cover the myosin-binding sites on actin troponin has Ca2+ binding sites organelle similar to ER network of tubes stores Ca2+ Ca2+ released from SR through channels Ca2+ restored to SR by Ca2+ pumps pump Ca2+ from cytosol pumps use ATP AP Biology ATP But what does the Ca2+ do? AP Biology 5 AP Biology The Trigger: motor neurons Motor neuron triggers muscle contraction release acetylcholine (Ach) neurotransmitter AP Biology Ca2+ triggers muscle action At rest, tropomyosin blocks myosin-binding sites on actin secured by troponin C 2+ Ca Nerve trigger of muscle action Nerve signal travels down T-tubule stimulates sarcoplasmic reticulum (SR) of muscle cell to release stored Ca2+ flooding muscle fibers with Ca2+ AP Biology How Ca2+ controls muscle Sliding filament model bi d to binds t troponin t i shape change causes movement of troponin releasing tropomyosin exposes myosinbinding sites on actin AP Biology exposed actin binds to myosin fibers slide past each other ATP ratchet system shorten muscle cell muscle doesn’t relax until Ca2+ is pumped back into SR muscle contraction requires ATP ATP AP Biology 6 AP Biology Put it all together… 1 How it all works… Action potential causes Ca2+ release from SR 2 Ca2+ binds to troponin Troponin moves tropomyosin uncovering myosin 3 binding site on actin Myosin binds actin ATP 7 4 6 ATP uses ATP to "ratchet" ratchet each time releases, "unratchets" & binds to next actin Myosin pulls actin chain along Sarcomere shortens Z discs move closer together Whole fiber shortens → contraction! Ca2+ pumps restore Ca2+ to SR → relaxation! ATP 5 AP Biology Fast twitch & slow twitch muscles Slow twitch muscle fibers contract slowly, but keep going for a long time more mitochondria for aerobic respiration long distance runner “dark” meat = more blood vessels Fast twitch muscle fibers contract quickly, but get tired rapidly store more glycogen for anaerobic respiration sprinter AP Biology “white” meat ATP Muscle limits Muscle fatigue lack of sugar low O2 lack of ATP to restore Ca2+ gradient lactic acid drops pH which interferes with protein function less SR → Ca2+ remains in cytosol y longer g pumps use ATP AP Biology synaptic fatigue loss of acetylcholine Muscle cramps AP Biology build up of lactic acid ATP depletion ion imbalance massage or stretching increases circulation 7 AP Biology Diseases of Muscle tissue ALS amyotrophic lateral sclerosis Lou Gehrig’s disease motor neurons degenerate Botox Bacteria Clostridium botulinum toxin blocks release of acetylcholine botulism can be fatal muscle Myasthenia gravis AP Biology auto-immune antibodies to acetylcholine receptors Stephen Hawking AP Biology Rigor mortis So don’t be a stiff! Ask Questions!! So why are dead people “stiffs”? no life, no breathing no breathing, no O2 no O2, no aerobic respiration no aerobic respiration respiration, no ATP 2+ pumps no ATP, no Ca 2+ Ca stays in muscle cytoplasm muscle fibers continually contract tetany or rigor mortis eventually tissues breakdown & relax AP Biology measure of time of death AP Biology 8 AP Biology Shortening sarcomere Myosin pulls actin Ghosts of Lectures Past (storage) chain along toward center of sarcomere Sarcomere shortens ((Z lines move closer together) Muscle contracts Z energy from: ATP glycogen AP Biology Z Z Z AP Biology 9
