42.1 The bodies of vertebrates are organized into functional systems.
Organization of the Body
• The vertebrate body plan is a tube within a tube. (p. 856)
• The four levels of organization in the vertebrate body are cells, tissues, organs, and organ systems. (p. 856)
• The four principal types of tissues are epithelial, connective, muscle, and nervous. (p. 856)
• An organ is a structural and functional unit composed of several different tissues, and an organ system is a group of cooperating organs. (p. 857)
42.2 Epithelial tissue forms membranes and glands.
Characteristics of Epithelial Tissue
• Epithelium covers every surface of the vertebrate body. (p. 860)
• Simple epithelial membranes are one cell layer thick, while stratified epithelial membranes are several layers thick and named according to the features of their uppermost layers. (p. 860)
• Exocrine and endocrine glands are derived from invaginated epithelium. (p. 860)
42.3 Connective tissues contain abundant extracellular material.
Connective Tissue Proper
• Connective tissue is divided into connective tissue proper, which is further divided into loose and dense connective tissue, and special connective tissues, which include cartilage, bone, and blood. (p. 862)
• Adipose cells can be found in loose connective tissue, and serve in nutrient storage. (p. 862)
Special Connective Tissues
• Cartilage is specialized connective tissue that is firm yet flexible. (p. 864)
• Bone is dynamic, living tissue formed by osteoblasts and is continually reconstructed throughout an individual's life. (p. 864)
• Bones are divided into flat bones and long bones, and long bones consist of spongy bone and compact bone. (p. 865)
• Skeletal bones support and protect the body, and serve as levers for contraction of skeletal muscles. (p. 865)
• Blood is a type of connective tissue that contains platelets and several types of cells within an abundant extracellular material, the fluid plasma. As plasma circulates, it carries nourishment and other regulatory molecules. (p. 866)
42.4 Muscle tissue provides for movement, and nerve tissue provides for control.
Muscle Tissue
• Muscles are unique due to the relative abundance and organization of actin and myosin filaments. (p. 867)
• Vertebrates have three types of muscle: smooth muscle, which powers involuntary movements of the viscera; skeletal muscle, which powers voluntary movement; and cardiac muscle, which powers the heartbeat. Skeletal and cardiac muscles are known as striated muscles, because they have transverse stripes when viewed under high magnification. (pp. 867-868)
Nerve Tissue
• Nerve cells include neurons, which produce, conduct, and receive electrical impulses, and supporting cells called neuroglia, which support and insulate neurons. (p. 869)
• The nervous system is divided into the central nervous system and the peripheral nervous system. (p. 869)
42.5 Coordinated efforts of organ systems are necessary for locomotion.
Organ Systems Involved in Animal Movement
• Animals are the only one of the three multicellular kingdoms to actively explore the environment. (p. 870)
The Skeletal System Supports Movement.
• The three types of skeletal systems in the animal kingdom are hydrostatic skeletons, exoskeletons, and endoskeletons. (p. 871)
Muscle Contractions Move Bones at Joints
• The three main classes of joints are immovable joints, slightly movable joints, and freely movable joints. (p. 872)
• Muscles that cause the same action at a joint are synergists, while muscles that produce opposing actions are antagonists. (p. 873)
• Isotonic contraction causes muscles to shorten, while isometric contraction causes no change in length. (p. 873)
42.6 Muscle contraction powers animal locomotion.
Muscle Contraction
• Each skeletal muscle contains numerous muscle fibers, and each muscle fiber encloses a bundle of myofibrils composed of thick and thin myofilaments. (p. 874)
• Thick myofilaments (myosin) form cross-bridges with thin myofilaments (actin) and pull the actin filaments along the thick filaments. The binding of ATP allows myosin to detach from actin and begin a new cross-bridge cycle, causing contraction of the myofibril. (pp. 874-876)
• When Ca++ binds to the protein troponin, the protein tropomyosin is displaced, and the myosin-binding sites or actin are exposed, allowing cross-bridge formation and muscle contraction. Stimulation of the muscle fibers by nerves causes the release of Ca++ from the sarcoplasmic reticulum in muscle fibers. (p. 878)
• A motor unit is a motor neuron plus the set of muscle fibers innervated by all axonal branches of that motor neuron. (p. 879)
• Recruitment refers to the nervous system's use of increased numbers and sizes of motor units to produce a stronger contraction. (p. 879)
• Skeletal muscle fibers can be divided on the basis of contraction speed into slow (type I) fibers or fast (type II) fibers. (p. 881)
Modes of Animal Locomotion
• Locomotion in large animals is almost always produced by appendicular locomotion, or bodies that undulate, axial locomotion. (p. 882)
• Locomotion in water presents a challenge because water's buoyancy reduces the influence of gravity; thus, the primary force retarding movement is frictional drag. (p. 882)
• Land animals exhibit a variety of locomotion styles, such as walking, running, leaping, and peristaltic movement. (p. 883)
• Flight has evolved among animals four times -- in insects, pterosaurs, birds, and bats. In all four groups, propulsion is achieved by pushing down against the air with wings. (p. 884)