Chapter 46: Animal sensory system and movment (pg.1095-1101)
Information about the environment is useless unless an animal can respond to it in an appropriate way,
usually by moving.
Locomotion, or the movement of an entire animal, is only one type of movement.
Skeletons provide attachment sites for muscles and a support system for the body’s soft tissues.
Exoskeletons are hard, hollow structures that envelop the body.
Hydrostatic skeletons use the pressure of internal body fluids to support the body.
Endoskeletons are hard structures inside the body that are composed of the connective tissues cartilage
Cartilage is made up of cells scattered in a gelatinous matrix of polysaccharides and protein fibres.
Bone is made up of cells in a hard extracellular matrix of calcium phosphate with small amounts of
calcium carbonate and protein fibres.
Bones meet and interact at articulations, or joints. Bones articulate in ways that allow limbs to swivel,
hinge, or pivot.
The ends of skeletal muscles are often attached to two different bones by bands of tough, fibrous
connective tissue called tendons.
Muscles can exert force only by contracting, so pairs of muscles must work together to move a bone
back and forth.
To move a limb, one muscle pulls the limb in one direction; the other muscle pulls it in the opposite
direction. This pairing of muscles is called an antagonistic muscle group.
The muscle that swings two long bones toward each other in an arc is a flexor; the muscle that
straightens them out is an extensor.
In all vertebrae animals, the movements of paired muscles are coordinated in brain or spinal cord. These
motor neurons projects from processing centres that receive input from sensory systems. How do muscles contract?
Vertebrate muscle tissue is composed of slender muscle fibers with small strands called myofibrils.
Sliding filament model
The sarcomere, the functional unit of skeletal muscle, appears as light and dark bands on the myofibril
These bands are made up of two types of filaments, thick filaments and thin filaments, which slide
past each other during muscle contraction (Figure 46.20).
This is known as the sliding–filament model.
The thin filaments are composed of two coiled chains of the globular protein actin.
The thick filaments are composed of multiple strands of a long protein called myosin.
A model for the interaction between myosin and actin during muscle contraction is shown in Figure