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Biology Sylvia S. Mader Michael Windelspecht Chapter 39 Locomotion and Support Systems Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Outline • 39.1 Diversity of Skeletons • 39.2 The Human Skeletal System • 39.3 The Muscular System 2 Diversity of Skeletons • Exoskeletons and Endoskeletons Exoskeleton – external skeleton • Molluscs – composed of calcium carbonate • Arthropods – composed of chitin – Animal must molt (shed their exoskeleton) in order to grow 3 Diversity of Skeletons • Exoskeletons and Endoskeletons Endoskeleton – internal skeleton • Echinoderms – Composed of spicules and plates of calcium carbonate embedded in the living tissue of the body wall • Sharks and Rays – Composed of cartilage • Bony fishes, amphibians, reptiles, birds, and mammals – Composed of bone and cartilage 4 Diversity of Skeletons • Exoskeletons and Endoskeletons Endoskeleton (continued) • Advantages: – – – – – Grows with the animal Supports the weight of large animals Protects vital internal organs Protected by outer tissues Allows flexible movements 5 Exoskeleton Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Michael Fogden/OSF/Animals Animals/Earth Scenes 6 The Vertebrate Endoskeleton Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Advantages of Jointed Endoskeleton Can grow with the animal Supports the weight of large animal Protects vital internal organs Is protected by outer tissues Allows flexible movements © E. R. Degginger/Photo Researchers, Inc. 7 39.2 The Human Skeletal System • Functions Support of the body Protection of vital internal organs Sites for muscle attachment Storage reservoir for ions Production of blood cells 8 The Human Skeletal System • Bone Growth and Removal Cartilaginous structures in early development act as models for future bones • Models are eventually converted to bones as calcium salts are deposited in the matrix by bone forming cells • Endochondral ossification – The conversion of cartilaginous models to bones 9 The Human Skeletal System • Bone Growth and Removal Osteoblasts - bone-forming cells • Synthesize new matrix Osteoclasts • Break down bone, remove worn cells, deposit calcium in the blood Osteocytes - mature bone cells • Osteoblasts that become caught in the matrix • Live within the lacunae of osteons 10 The Human Skeletal System • Anatomy of a Long Bone Gross anatomy • Medullary cavity in center bounded by – Compact bone at the sides – Spongy bone at the ends Details • Compact bone – Unit of structure called osteon (Haversian systems) – Concentric lacunae arranged around a central canal – Lacunae separated by a matrix of collagen fibers and mineral deposits • Spongy bone – Numerous bars and plates separated by irregular spaces – Spaces filled with red bone marrow, which produces blood cells 11 The Muscular System • Microscopic Anatomy and Physiology Sarcolemma • Plasma membrane Sarcoplasmic Reticulum • Modified endoplasmic reticulum • Stores calcium ions Myofibrils • Contractile structures in the sarcoplasm Sarcomeres • Units of contraction within myofibrils • Consist primarily of two types of protein filaments – Thick filaments made of myosin – Thin filaments made of actin 12 The Muscular System • Sliding Filament Model Actin filaments are found at both ends of sarcomere • One end of each filament is attached to a Z line at one end of the sarcomere • The other end suspended in sarcoplasm Myosin filaments are suspended between Z lines 13 The Muscular System • Sliding Filament Model (continued) When a muscle fiber contracts, • Actin filaments slide past the myosin filaments and approach one another • Causes the Z lines to move toward each other • The sarcomeres shorten • The filaments remain the same length 14 The Muscular System • Sliding Filament Model (continued) When a muscle fiber contracts, • Actin filaments slide past the myosin filaments and approach one another • Causes the Z lines to move toward each other • The sarcomeres shorten • The filaments remain the same length Working muscles require ATP • Myosin filaments break down ATP and form crossbridges that pull actin filaments toward the center of the sarcomere • Sustained exercise requires cellular respiration to regenerate ATP 15 The Muscular System • Use of ATP in Contraction Cellular respiration does not immediately supply all of the ATP that is needed within a cell Muscle fibers rely on creatine phosphate • Regenerates ATP through the following process: Creatine-P + ADP ATP + creatine When creatine phosphate is depleted and the cell still needs more ATP for muscle contraction to occur, it undergoes fermentation 16 Skeletal Muscle Fiber Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A muscle contains bundles of muscle fibers, and a muscle fiber has many myofibrils. bundle of muscle fibers myofibril 17 (gymnast): © Corbis RF Skeletal Muscle Fiber Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A muscle contains bundles of muscle fibers, and a muscle fiber has many myofibrils. bundle of muscle fibers myofibril (gymnast): © Corbis RF 18 Skeletal Muscle Fiber Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A muscle contains bundles of muscle fibers, and a muscle fiber has many myofibrils. bundle of muscle fibers myofibril sarcolemma mitochondrion one myofibril sarcoplasm skeletal muscle fiber Z line T tubule sarcoplasmic reticulum crossbridge one sarcomere Z line nucleus myosin actin H zone Z line Sarcomeres are contracted. A band 6,000X I band Sarcomeres are relaxed. (gymnast): © Corbis RF; (myofi bril): © Biology Media/Photo Researchers,Inc. A myofibril has many sarcomeres. 19 Accidental Discovery of Botox • The botulism toxin is produced by the bacterium Clostridium botulinum One of the most lethal substances known By the 1920’s the toxin had been isolated in pure form • The pure form allowed scientists to determine that the toxin acted by preventing nerves from communicating with muscles • Scientists soon began using the toxin to treat conditions in which the muscles contract too much – Eye conditions and spasms of facial muscles 20 Accidental Discovery of Botox • Canadian ophthalmologist Jean Carruthers used the toxin to treat her patients’ eye conditions She soon noticed that the treatment caused the facial wrinkles on her patient to subside She convinced her husband, a dermatologist, to use the toxin to reduce wrinkles in his patients • The treatment was successful and the toxin is now FDA approved and used throughout the country 21 The Muscular System • Muscle Innervation Neuromuscular junction • The synaptic contact between a nerve fiber and a muscle fiber • Nerve impulses bring about the release of a neurotransmitter called acetylcholine (ACh) that crosses the synaptic cleft • Acetylcholine signals the muscle fiber to contract 22 Neuromuscular Junction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. skeletal muscle fiber axon branch axon terminal myofibril neuromuscular junction synaptic vesicle a. One motor axon causes several muscle fibers to contract. synaptic cleft acetylcholine (ACh) muscle fiber axon branch plasma membrane of axon axon terminal acetylcholinesterase (AChE) Na+ synaptic vesicle folded sarcolemma synaptic cleft sarcolemma ACh receptor mitochondrion myofibril nucleus b. A neuromuscular junction is the juxtaposition of an axon terminal and the sarcolemma of a muscle fiber. c. The release of a neurotransmitter (ACh) causes receptors to open and Na+ to enter a muscle fiber. © Victor B. Eichler, Ph.D. 23 The Muscular System • Role of Calcium in Muscle Contraction Acetylcholine binds to receptors in the sarcolemma The sarcolemma generates impulses that spread down T tubules to the sarcoplasmic reticulum Calcium is released from the sarcoplasmic reticulum Calcium ions bind with troponin Troponin regulates the position of tropomyosin, which can block myosin binding sites on actin filaments 24 The Role of Calcium and Myosin in Muscle Contraction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. actin filament troponin myosin binding sites Ca2+ Ca2+ Troponin-Ca2+ complex pulls tropomyosin away, exposing myosin binding sites. tropomyosin a. Function of Ca2+ actin filament P ADP myosin filament cross-bridge myosin head 1 ATP is hydrolyzed when myosin head is unattached. ATP 4 2 ADP + P are bound to myosin as myosin head attaches to actin. Binding of ATP causes myosin head to assume resting position. 3 Upon ADP + P release, power stroke occurs: head bends and pulls actin. b. Function of myosin 25