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Frolich, Human Anatomy, Mechanics of Movement Mechanics of Movement II: Muscle Action Across Joints Review muscle force generation Muscle Physics --force.

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Presentation on theme: "Frolich, Human Anatomy, Mechanics of Movement Mechanics of Movement II: Muscle Action Across Joints Review muscle force generation Muscle Physics --force."— Presentation transcript:

1 Frolich, Human Anatomy, Mechanics of Movement Mechanics of Movement II: Muscle Action Across Joints Review muscle force generation Muscle Physics --force versus cross section --length versus strain Lever mechanics Stabilizing the jointisometric and eccentric contraction

2 Frolich, Human Anatomy, Mechanics of Movement Muscle Structure Review Muscle fiber = muscle cell Fibers lined up = direction of pull Tendon attaches to bone Muscle pulls on bone Fig. 10.1

3 Frolich, Human Anatomy, Mechanics of Movement Muscle Origin and Insertion Origin Proximal Fixed Insertion Distal Moves (usually!!) Fig. 10.3

4 Frolich, Human Anatomy, Mechanics of Movement Mechanics of Contraction Muscle cell is unit Role of actin/myosin Action potential or depolarization of membrane makes cell contract (motor neuron action potential stimulates muscle membrane depolarization) Fig. 10.4

5 Frolich, Human Anatomy, Mechanics of Movement Visualizing muscle contraction Fig How actin- myosin complex (sarcomere) shorten muscle

6 Frolich, Human Anatomy, Mechanics of Movement Summary of Muscle Organization/Function

7 Frolich, Human Anatomy, Mechanics of Movement Summary of Muscle Organization/Function

8 Frolich, Human Anatomy, Mechanics of Movement Summary of Muscle Organization/Function

9 Frolich, Human Anatomy, Mechanics of Movement Table 10.2 Levels of Muscle Organization

10 Frolich, Human Anatomy, Mechanics of Movement Muscle Physics: Principle I Cross sectional area is proportional to Force of muscle

11 Frolich, Human Anatomy, Mechanics of Movement Muscle Physics: Principle II Length of muscle is proportional to ability to shorten (strain) Number of sarcomeres in series gives shortening ability Short, fat muscles Lots of force Less shortening range Long, skinny muscles Less force More shortening range

12 Frolich, Human Anatomy, Mechanics of Movement Muscle Physics: Principle III Force generation depends on current length of muscle or overlap in actin/myosin of sarcomeres Muscle force strongest between % of normal resting length WHY? (dont forget role of cross-bridges) Most muscles arranged to work in this range

13 Frolich, Human Anatomy, Mechanics of Movement Types of fascicle arrangements Affects length and cross section of muscle Thus affects force and shortening properties of muscle See Muscle Physics Principles I-III if this doesnt make sense Fig. 11.3

14 Frolich, Human Anatomy, Mechanics of Movement Muscle movement across joints is like lever system Fig. 11.1

15 Frolich, Human Anatomy, Mechanics of Movement First-class lever Fig. 11.2

16 Frolich, Human Anatomy, Mechanics of Movement Second-class lever Fig. 11.2

17 Frolich, Human Anatomy, Mechanics of Movement Third-class lever Fig. 11.2

18 Frolich, Human Anatomy, Mechanics of Movement Stabilization and Control Around Joint AgonistMain MoverE.g. biceps AntagonistOpposite motion E.g. triceps SynergistAids agonistE.g. brachialis Antagonist often fires or contracts or is stimulated simultaneously with agonist to stabilize around joint during movement NOTE: Muscle contraction or stimulus to fire does not always result in muscle shortening

19 Frolich, Human Anatomy, Mechanics of Movement Agonist/Antagonist

20 Frolich, Human Anatomy, Mechanics of Movement Relation between muscle contraction (or firing) and shortening Concentric contractionmuscle contracts and shortens to cause movement across joint Isometric contractionmuscle contracts but stays same length to hold joint or body in same position Eccentric contractionmuscle contracts while lengthening to stabilize joint during movement (most common in antagonist to slow movement caused by agonist)


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