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THE MUSCULAR SYSTEM LEARNING GOALS • I will be able to identify the functions, characteristics and types of muscle. • I will understand the terms associated with muscle naming and function. FUNCTIONS • Locomotion – All body movements and many body functions (arms, heart, intestines…). • Posture – Even when relaxed muscles are working to keep you upright (neck, lower back…) • Heat production – Body needs a basal temperature and muscles keep this by releasing heat as a by-product of reactions. CHARACTERISTICS • Irritability: Sensitive to nervous stimuli • Contractility: Responds to stimuli by shortening • Extensibility: Can be stretched when relaxed • Elasticity: Return to normal length when relaxed 3 TYPES OF MUSCLE • Muscle makes up 30-35% (in women) and 42-47% (in men) of body mass. • Smooth • Cardiac • Skeletal 1. SMOOTH (VISCERAL) MUSCLE • usually found in hollow internal organs (stomach, intestines bladder) • involuntary muscle • lacks the appearance of striations • SM cells shorter than skeletal muscle cells 2. CARDIAC • Occurs only in the heart • Controlled involuntarily • Can continue to function without nerve impulses • striated in appearance and the cells are joined end to end • Very fatigue resistant 3. SKELETAL • Over 400 • Contraction is voluntary • Striated in appearance (alternating dark and light bands) • When stimulated by a nerve fibre it contracts and relaxes • Includes both fast twitch and slow twitch fibers • attached to bones; responsible for movement • Also used in talking, breathing, swallowing and singing. MUSCLE ATTACHMENT • Muscle attaches to bone either directly or indirectly. INDIRECT ATTACHMENT • When attached indirectly, the epimysium that surrounds the exterior of the muscle fibre extends past the muscle as a tendon and then attached to the periosteum. DIRECT ATTACHMENT • When attached directly, the epimysium fuses with the periosteum. CONNECTIVE TISSUE • Tendons and ligaments are connective tissue that help to improve the stability of the joint. • In order for muscles to contract, they must be attached to the bones to create movement • A tendon is a connective tissue that attaches the muscle to the bone. CONNECTIVE TISSUE • Ligaments are tough connecting tissue that run from bone to bone limiting the movement of the joint and helps to maintain the stability of the joint. • Tendons and ligaments are not very elastic and lose their ability to perform correctly when stretched. • If repeatedly stretched or torn, surgery may be necessary to repair the damage. ACTIONS OF MUSCULAR SYSTEM • movement a muscle causes depends on where it is attached to a bone and how it is crosses a joint. • ORIGIN: Immovable end (proximal end) • INSERTION: The moveable end of the joint (distal end) • When a muscle contracts, its insertion is pulled toward its origin. • For example, when you contract your biceps, you pull your forearm towards your shoulder, so you are pulling towards the origin. • The insertion is on the radius, called the radial tuberosity, and it is the forearm that moves during contraction. AGONIST AND ANTAGONIST MUSCLE PAIRS • Muscles pull. They never push. • Skeletal muscles typically arranged as opposing pairs. • AGONIST: muscle primarily responsible for movement of a body part • ANTAGONIST: muscle that counteracts the agonist, lengthening when the agonist muscle contracts. • Many muscles are paired in agonist – antagonist relations • (Ex. Bicep and Triceps) MUSCLE DEVELOPMENT • Most muscles have formed by the 8th week of pregnancy. • Most women can feel movement by the 17th week of pregnancy. • At birth you have a fixed amount of muscle cells. • Growth of muscle cells depend on their use. • Atrophy – decrease in muscle cell diameter due to neglect of stimulation • Hypertrophy – increase in muscle cell diameter due to stimulation LEARNING GOALS • I will be able to identify the functions, characteristics and types of muscle. • I will understand the terms associated with muscle naming and function.