Transcript Antagonist
Skeletal Muscle Shapes Muscle Descriptions • Fusiform muscles – thick in middle and tapered at ends • Parallel muscles have parallel muscle fibers • Convergent muscle – broad at origin and tapering to a narrower insertion Muscle Descriptions Cont…. • Pennate muscles – fascicles insert obliquely on a tendon – unipennate, bipennate or multipennate • Circular muscles – ring around body opening (ex: iris, mouth) Interactions of Skeletal Muscles • Muscles can only pull, they can’t push • Actions must be “undone” by a different muscle • Muscles that produce opposite movements usually lie on opposite sides of a given joint Muscles Work together to move a joint • Agonist: “prime mover”, major responsibility for producing a specific movement Antagonist Agonist • Antagonist: oppose or reverse a particular movement – Usually contract a little to prevent overshooting the mark or slow the agonist’s action near the end – Are being “stretched” or can remain relaxed when agonist works • Antagonists for one movement can be agonists for another • Synergists help prime movers – Add a little extra force to the same movement – Or reduce undesirable extra movements (e.g. making a fist without flexing at wrist) • Fixators: hold a bone firmly so agonist has a stable base on which to move a body part (e.g. fixing scapula when arm moves) Muscles work in concert… the elbow Flexion • Prime Movers: responsible for flexing arm) – Biceps Brachii (lifts radius in forearm) – Brachialis (lifts ulna in forearm) • Synergists: helps stabilizes elbow joint – Brachioradialis • Antagonists: (resists movement of prime movers) – Triceps Brachii • Fixators: (hold shoulder in place) – Deltoid – Trapezius Type of Contractions • Isometric Contraction – Muscles are contracting but there is no movement – Muscles trying to allow for body movement but can’t – spinning wheels • Isotonic Contractions – Movement occurs when muscles contract • Bending knee, smiling, rotating arms Pushing on a wall Lifting weights