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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 - PowerPoint PPT Presentation
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• 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
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: 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
Antagonist
Agonist
• 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