Internal skeleton, composed of mineralized bone and cartilage, grows as the animal grows, does not limit space for internal organs, supports greater weight, adapted to individual organisms' particular mode of locomotion
Thick outer cylinder of compact bone, medullary cavity in center with yellow bone marrow, spongy bone at ends, unit of structure called osteon with concentric lamellae arranged around central canal, osteocytes lie in lacunae at lamellar boundaries, spongy bone has numerous bars and plates separated by irregular spaces designed for strength, spaces filled with red bone marrow
Formed by cranium and facial bones, major bones named after lobes of the brain and facial bones, foramen magnum at base of skull where spinal cord connects to brain, bones of cranium surround sinuses
Supports the head and trunk, protects the spinal cord and roots of spinal nerves, segments include cervical, thoracic, lumbar, sacral, and coccyx, intervertebral disks of fibrocartilage act as padding
Protects the heart and lungs, and assists breathing, supported by the thoracic vertebrae, twelve pairs of ribs including seven pairs of true ribs that connect directly to the sternum and five pairs of "false" ribs that do not connect directly to the sternum
Composed of fibers in bundles, each fiber has a sarcolemma (plasma membrane) that forms a transverse system with sarcoplasmic reticulum (modified endoplasmic reticulum) that stores calcium ions for contraction, myofibrils in sarcoplasm are the contractile structures
1. Actin filaments at both ends of sarcomere, one end attached to Z-plate, other end suspended in sarcoplasm
2. Myosin filaments suspended in between Z-plates, contain cross-bridges that pull actin filaments inward, causing Z-plates to move toward each other and sarcomere to shorten
3. Sarcomeres stacked together in series cause myofiber to shorten
4. Working muscles require ATP, myosin breaks down ATP, sustained exercise requires cellular respiration to regenerate ATP
Region containing nerve axon terminal, sarcolemma, and synaptic cleft where nerve impulses bring about the release of a neurotransmitter that crosses the synaptic cleft and signals the muscle fiber to contract, acetylcholinesterase breaks down acetylcholine to end contraction
Ca2+ binds to troponin on actin, exposing myosin binding sites, myosin hydrolyzes ATP resulting in movement of myosin heads that pull actin filament, new ATP binds to heads causing release, process continues until nerve stimulation ends