Lecture 3 movement 2nd sem 2008-2009
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Lecture 3 movement 2nd sem 2008-2009

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Lecture 3 movement 2nd sem 2008-2009 Lecture 3 movement 2nd sem 2008-2009 Presentation Transcript

  • Lecture 3. MovementThree principal kinds of movement: – ameboid – ciliary and flagellar – muscular
  • Ameboid Movement– amebas and other unicellular forms– white blood cells– embryonic mesenchyme cells– other mobile cells
  • Fig. 11.5a
  • Fig. 11.5c
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 1. hyaline cap appears
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 2. endoplasm flows toward hyaline cap
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 3. actin subunits attach to regulatory proteins
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 4. endoplasm fountains out to the periphery
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 5. actin subunits released and polymerized
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 6. microfilaments cross-linked
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 7. Ca2+ activate actin-severing protein
  • Consensus model to explain extension and withdrawal of pseudopodia and ameboid crawling: 8. myosin associate with and pull on microfilaments
  • Ciliary and Flagellar MovementCilia – minute, hairlike, motile processes – occur in large numbers – ciliate protistans – found in all major groups of animals – move organisms through aquatic environment – propel fluids and materials across surfaces
  • Ciliary and Flagellar MovementFlagella – whiplike – present singly or in small numbers – occur in unicellular eukaryotes – animal spermatozoa – sponges
  • • both cilia and flagella have the same ultrastructure – a core of microtubules sheathed by the plasma membrane
  • • both cilia and flagella have the same ultrastructure – “9 + 2” pattern – flexible “wheels” of proteins connect outer doublets to each other and to the core
  • • both cilia and flagella have the same ultrastructure – outer doublets are connected by motor proteins – anchored in the cell by a basal body
  • • The bending of cilia and flagella is driven by the arms of a motor protein, dynein.
  • • Addition to dynein of a phosphate group from ATP and its removal causes conformation changes in the protein.• Dynein arms alternately grab, move, and release the outer microtubules.
  • • Protein cross-links limit sliding and the force is expressed as bending.
  • • A flagellum has an undulatory movement – force is generated parallel to the flagellum’s axis
  • • Cilia move more like oars with alternating power and recovery strokes – generate force perpendicular to the cilia’s axis
  • Invertebrate MuscleBivalve molluscan muscles – 2 kinds of fibers: • fast muscle fibers = striated, can contract rapidly • smooth muscle = capable of slow, long-lasting contractions
  • Invertebrate MuscleInsect flight muscles (fibrillar muscle) – wings of small flies operate at 1000 beats/sec – limited extensibility; shorten only slightly
  • Vertebrate MuscleTypes1. Striated2. Smooth3. Cardiac
  • Structure of Striated Muscle
  • Sliding Filament Model• Actin filaments at both ends of sarcomere – one end of each filament attached to a Z-plate at one end of the sarcomere – other end suspended in sarcoplasm
  • Sliding Filament Model• Myosin filaments suspended in between Z-plates – myosin filaments contain cross-bridges which pull the actin filaments inward – causes Z-plates to move toward each other – shortens sarcomere – sarcomeres stacked together in series and cause myofiber to shorten
  • Sliding Filament Model• Working muscles require ATP – myosin breaks down ATP – sustained exercise • requires cellular respiration • regenerates ATP
  • 35 Muscle Innervation • Neuromuscular junction – the synaptic contact between a nerve fiber and a muscle fiber – nerve impulses bring about the release of a neurotransmitter that crosses the synaptic cleft – signals the muscle fiber to contract
  • Human Muscular System• Skeletal muscles – attached to the skeleton by cable-like fibrous connective tissue called tendons – arranged in antagonistic pairs • can only contract, cannot push • when one muscle contracts, it stretches its antagonistic partner• a muscle at “rest” exhibits tone (minimal contraction)• a muscle in tetany is at maximum sustained contraction
  • 43
  • Muscle Performance– slow oxidative fibers (red muscles) • for slow, sustained contractions without fatigue • contain extensive blood supply • high density of mitochondria • abundant stored myoglobin • important in maintaining posture in terrestrial vertebrates
  • Muscle Performancefast fibers 1. fast glycolytic fiber (white muscles) • lacks efficient blood supply • pale in color • function anaerobically • fatigue rapidly 2. fast oxidative fiber • extensive blood supply • high density of mitochondria and myoglobin • function aerobically • for rapid, sustained activities
  • Energy for Contraction– ATP, immediate source of energy– glucose broken down during aerobic metabolism– glycogen stores can supply glucose– muscles have creatine phosphate, an energy reserve– slow and fast oxidative fibers rely heavily on glucose and oxygen– fast glycolytic fibers rely on anaerobic glycolysis– muscles incur oxygen debt during anaerobic glycolysis