Essentials of Human Anatomy Physiology Elaine N Marieb
Essentials of Human Anatomy & Physiology Elaine N. Marieb BIOL 2401 Unit 3: The Muscular System Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
INTERACTIONS OF SKELETAL MUSCLES IN THE BODY
Some of the details to think about: You will have a few muscles indicated in lab to learn the origin, insertion & action of.
Muscle Interactions · Prime mover (Agonist) – muscle with the major responsibility for a certain movement · Antagonist – muscle that opposes or reverses a prime mover Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 35
Muscle Interactions · Synergist – muscle that aids an agonist in a movement and helps stabilize the motion · Fixator – synergists that helps immobilize a bone or muscle origin (while the insertion point moves) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 35
Coordination n Actions of antagonistic and synergistic muscles are important in causing smooth, coordinated, and precise muscle motions.
NAMING OF SKELETAL MUSCLES
Naming of Skeletal Muscles · Location of the muscle – named for a bone or region with which they are associated · Temporalis · Shape – named for a distinctive shape · Deltoid (triangular) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide
Naming of Skeletal Muscles · Relative size of the muscle · Maximus (largest) & Minimus (smallest) · Longus (longer in length than in diameter) & Brevis (short) · Direction of muscle fibers · Rectus (straight) · Oblique (at an angle) · Transversus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide
Naming of Skeletal Muscles · Number of origins · Biceps, triceps, quadriceps (# of heads) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide
Naming of Skeletal Muscles · Location of the muscles origin and insertion (attachment points) · Example: sternocleidomastoid (on the sternum, clavicle, and mastoid process) · Action of the muscle · Example: flexor and extensor (flexes or extends a bone) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 6. 37
Fascicle Arrangement MUSCLE MECHANICS
Fascicle Arrangment n n n The direction and arrangement of the muscle fiber bundles (aka: fascicles) is important to observe. These factors determine what a muscle can do and what it is best for. Fascicle arrangement is also important to take note of in order to maximize the efficiency of your workouts (discusssed later)
Fascicle Arrangement n Range of Motion n Longer muscle fibers along muscle axis = greater range of motion n Parallel fascicle arrangement gives greatest ROM n Movement n Convergent muscle arrangement is best for moving large areas of the body
Fascicle arrangment n Strength (Power) n Depends on # of Muscle fibers n Greater # = greater power n Bipennate – shorten very little but have a greater # of muscle fibers collectively so best for strength n Circular muscles cause both internal and external body openings to: Open when relaxed n Close when contracted n Aka. Sphincter muscles n
Fascicle Arrangement – see notes
Lever Actions MUSCLE MECHANICS
Biomechanics Muscles exert force by use of lever action n Bones act as levers for muscles to pull on. Each type of lever has advantages and disadvantages in either the strength required to move the body part or the distance (ROM) that the body part can be moved or the speed of the motion. n
Modifying muscle activity n Differences in the positioning of the fulcrum. load, and effort modify muscle activity with respect to: n speed of contraction n Direction of motion n range of motion (ROM) n Strength - weight that can be lifted
Terms to understand n n n Effort – applied force – provided by muscle contraction Load – resistance – bone, overlying tissues, and any other object you are trying to move Fulcrum – fixed point - joints
Power vs. Speed n Mechanical advantage: power levers Load close to fulcrum n Effort far from fulcrum n Small effort x large distance n Large load x small distance n
Power vs. Speed n Mechanical disadvantage: speed levers Load far from fulcrum n Effort close to fulcrum n Large effort x large load x large distance n
First class lever n n Fulcrum is in the middle - between load and effort The main advantage is the change in direction of the force – force exerted is equal to force lifted Example: Muscle pulls downward to lift body part upward or vice versa Example: Extension of head
Second class lever n n n Load is in the middle - between effort and fulcrum Uncommon in the body The main advantage is multiplication of force (strength)– force exerted is less than force lifted Levers of power BUT Range of motion is sacrificed Example: n Standing on your toes (contraction of calf muscle) lifts your whole body but only a small distance
Third class lever n n n Effort is in the middle - between load and fulcrum Most common in the body Lever of speed: main advantage is range of motion n n Strength is sacrificed & Speed is gained Example: n Flexing at elbow using bicep muscle
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