Animal Locomotion. Lots of ways to get around. What are the advantages of locomotion? Why Do We Need All That ATP?

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1 Animal Locomotion What are the advantages of locomotion? Motor Mechanisms sessile (Muscles & Motor Locomotion) motile Why Do We Need All That ATP? mollusk mammal bird reptile

2 We saw how some organisms use cilia, flagella, or pseudopodia to move. Now we will will look at another adaptation: MUSCLE TISSUE bird arthropod mammal bird voluntary, striated moves bone multi-nucleated involuntary, striated auto-rhythmic heart Connected through gap junctions evolved first involuntary, non-striated digestive system arteries, veins! Muscles are the effectors of nervous system outputs " To move an animal, however, skeletal muscles must work with the skeleton! Provides support against gravity! Provides protection of soft tissue from injury # Skull around brain # Rib cage around heart and lungs! Provides a rigid structure to which muscles can attack # Muscles exert force only during contraction # Moving body part requires muscles be attache to in two places to skeleton " Hydrostatic skeleton - fluid held under pressure in a closed body compartment! Ex: Cnidarians, flatworms, nematodes, annelids! Muscles in body walls exert localized forces against hydrostatic skeleton # Hydrostatic skeletons support crawling and burrowing and cushion organs $ Hydrostatic skeletons cannot support terrestrial activities in which the body needs to be held off ground like walking or running " Exoskeleton - hardened support structure on exterior of animal! Ex: Molluscs secrete calcium carbonate shell from mantle Arthopods secrete chitin and proteins from epidermis $ In arthropods, muscles are attached to knobs and plates and extend into interior of body " Endoskeleton - hardened support structure in soft tissue interior of animal! Ex: Sponges have hard needle-like structures of inorganic materials and protein fibers around cells! Ex: Echinoderms have hard plates of calcium carbonate or magnesium carbonate called ossicles beneath skin! Ex: Chordates have skeletons consisting of cartilage, bone or a combination

3 Human endoskeleton 206 bones Movement in multiple planes " Various muscles cooperate to move bone in one direction under control of the nervous system Some bones are fused together, others connected at joints by ligaments that allow freedom of movement Allows rotation Movement in single plane! Muscles move bones by contracting # Shortening the muscle cells Muscles movement! skeletal muscles come in antagonistic pairs! flexor vs. extensor # When one muscle contracts the antagonistic muscle relaxes and vice versa " contracting = shortening! move skeletal parts! tendons # connect bone to muscle! ligaments # connect bone to bone " Contraction is active & needs energy! Extension is passive Flexors Extensors

4 tendon Organization of Skeletal muscle skeletal muscle Muscle fiber bundles muscle fiber (elongated cell) Multiple Nuclei (due to fusion of embryonic cells) plasma Membrane (a.k.a. the sarcolemma) myofibrils Myofilaments (thin & thick filaments) Structure of striated skeletal muscle! Muscle Fiber (Myofiber) = muscle cell! Contains long myofibrils # Divided into sections = sarcomeres! Sarcomere " functional unit of muscle contraction! Basic unit of contraction # Alternating overlapping bands of thin (actin) & thick (myosin) protein filaments Z Muscle filaments & Sarcomere M M - line Thin and thick filaments partially overlap Z Striated appearance caused by arrangement of protein filaments! Interacting proteins: " thin filaments (Attached to Z lines)! 2 braided strands of ACTIN! 2 braided strands of regulatory protein (not shown) # tropomyosin # troponin " thick filaments (Attached to M lines)! MYOSIN # Fibers arrange in staggered arrays Thin filaments: Actin-based! Complex of proteins " 2 strands each of actin fibers & tropomyosin fibers! tropomyosin fibers secured with troponin molecules " The actin has binding sites for the heads of myosin fibers! During relaxation = binding sites on actin are blocked by the tropomyosin

5 Thick filaments: myosin! Each myosin is a singe protein (not globular polypeptides arranged sequentially like actin) " myosin molecule = long protein with globular head! Thick filament " Staggered arrays of myosin molecules with heads sticking out Thick & thin filaments of one sarcomere! Myosin tails are aligned together! Myosin heads point away from the center of sarcomere M - line bundle of myosin proteins: AP globular Biology heads aligned Interaction of thick & thin filaments! Sliding-filament model of muscle contraction " Neither thin nor thick filament change in length when sarcomere shortens! Filaments slide past each other longitudinally # Overlap of thin and thick filaments increases! How is this accomplished? " By forming Cross Bridges! Connections formed between myosin heads (of thick filaments) & actin (of thin filaments) # Thin filament are then pulled towards center of sacromere, along thick filament $ Causes the muscle to shorten (contract) sarcomere sarcomere Where is ATP needed? ATP Cycle So that s where those 10,000,000 ATPs go! Well, not all of it! 1 1 Myosin binds ATP (low E state) myosin head Cleaving ATP! ADP allows myosin head to bind to actin filament 12 ATP 1 form cross bridge 1 4 Head hydrolyzes ATP & switches to a high E state binding site ADP thin filament (actin) thick filament (myosin) ADP 3 ADP & P i are released: Head returns to low E state & slides thin filament