RTC’s for Chapters 41-44
1. Three types of skeletons occur in the animal kingdom. A fluid-filled gastrovascular cavity or coelom can act as a hydrostatic skeleton. An exoskeleton is an external skeleton. Vertebrates have an endoskeleton composed of bone and cartilage that grows with the animal. A hydrostatic skeleton occurs in cnidarians, flatworms, roundworms and annelids. An exoskeleton is found in molluscs and arthropods, respectively. An endoskeleton is found in sponges, echinoderms, and vertebrates.
2. Skeletons protect organs: skull (brain), vertebral column (spinal cord), and rib cage (heart and lungs). The large, heavy leg bones support the body against the pull of gravity. Leg and arm bones permit flexible body movement. The flat bones of the skull, ribs, and breastbone contain red bone marrow that manufactures blood cells.
3. A long bone consists of a central medullary cavity surrounded by compact bone. Ends are composed of spongy bone surrounded by a thin layer of compact bone and covered with hyaline cartilage. Compact bone contains many osteons (Haversian systems); bone cells in tiny chambers (lacunae) are arranged in concentric circles around central canals. Spongy bone has numerous plates and bars separated by irregular spaces. Spongy bone is lighter but designed for strength; solid portions of bone follow the lines of stress.
4. The axial skeleton lies at the midline of the body and consists of the skull, vertebral column, sternum and ribs. The appendicular skeleton consists of the bones within the pectoral girdle and upper limbs and the pelvic girdle and lower limbs.
5. Some of the bones that forms the pectoral girdle are the humerus, radius, and ulna. In the upper limb is where the collarbone is located. The pelvic girdle consists of two heavy, large coxal bones. The bones that make up this part are the femur, tibia, fibula, tarsal bones, metatarsal bones, and phalanges.
6. Bones are joined at joints that are classified as fibrous, cartilaginous, or synovial. Synovial joints are freely movable. Most joints are synovial joints, with the two bones separated by a cavity. Ligaments are fibrous connective tissue that bind bone to bone, forming a joint capsule. In a "double-jointed" individual, the ligaments are unusually loose. The joint capsule is lined with a synovial membrane that produces a lubricating synovial fluid.
7. Skeletal muscle contraction assists homeostasis by helping maintain constant body temperature. Skeletal muscle contraction also causes ATP breakdown, releasing heat that is distributed about the body. If a muscle is given a rapid series of stimuli, it responds to the next stimulus before completely relaxing. Muscle contraction summates until it reaches a maximal sustained contraction, called tetanus.
8. Skeletal muscles are attached to the skeleton by tendons made of fibrous connective tissue. When muscles contract, they only shorten or pull; therefore, skeletal muscles must work in antagonistic pairs. One muscle of an antagonistic pair bends the joint and brings a limb toward the body. The other one straightens the joint and extends the limb.
9. Sliding filament model: actin filaments slide past myosin filaments because myosin filaments have cross-bridges that pull actin filaments inward, toward their Z line. The contraction process involves the sarcomere shortening although the filaments themselves remain the same length. ATP supplies the energy for muscle contraction. Myosin filaments break down ATP to form cross-bridges that attach to and pull the actin filaments toward the center of the sarcomere.
10. Muscle cells contain myoglobin that stores oxygen; cellular respiration does not immediately supply all of the ATP needed. Muscle fibers rely on a supply of stored creatine phosphate (phosphocreatine), a storage form of high-energy phosphate. When all creatine phosphate is depleted, and if O2 is in limited supply, fermentation produces a small