The Muscular System Study Guide PDF

Preview

Summary

The Muscular System Study Guide...

Description

Ch 10 The Muscular System Understanding the anatomy of skeletal muscles will improve your body mechanics and help avoid injury to yourself and your patient Muscle Actions and Interactions 



Muscle tissue consists of all contractile tissues o Skeletal o Cardiac o Smooth Skeletal muscle looks at o Principles of leverage o How muscles interact to bring about movement o Criteria for naming muscles • • • •

Lever Systems Muscles pull on bones creating movement at an articulation Most skeletal muscles move using leverage Components of lever system o Lever: rigid bar (bone) that moves on a fixed point called fulcrum (joint) o Effort: force (supplied by muscle contraction) applied to lever to move resistance (load) o Load: resistance (bone + tissues + any added weight) moved by the effort Muscle Actions and Interactions • • •

• •

Muscles can only pull; never push What one muscle group “does,” another “undoes” Functional groups Prime mover(agonist) Major responsibility for producing specific movement o Ex. –the Biceps brachii contract; the arm flexes

Antagonist Opposes or reverses particular movement o Ex. –Triceps Brachii oppose the bicep brachii • During flexion or the prime movement, the antagonist is actively inhibited. o The prime mover for the opposite activity: The Triceps brachii contract for extension. • To lock a joint in place, both will simultaneously contract • Prime mover and antagonist are located on opposite sides of joint across which they act

•

•

•

Synergist helps prime movers o Adds extra force to same movement o Reduces undesirable or unnecessary movement Fixator o Synergist that immobilizes bone or muscle’s origin o Gives prime mover stable base on which to act Functional Groups o Same muscle may be:  Prime mover of one movement  Antagonist for different movement  Synergist for third movement

Skeletomuscular InteractionsAttachment points •

Origin- is the fixed aspect o May be proximal

•

Insertions- is the movable aspect o May be distal

Naming Skeletal Muscles • Muscle location- bone or body region with which muscle is associated o Example- temporalis (over temporal bone), occipitalis, frontalis, etc

•

Muscle shape- distinctive shapes o Example- deltoid muscle (deltoid = triangle)

•

Muscle size o Example- maximus (largest), minimus (smallest), longus (long)

•

Direction of pull (muscle fibers or fascicles) o Example- rectus (fibers run straight), transversus (fibers run at right angles), and oblique (fibers run at angles to imaginary defined axis)

•

Number of origins o Example- biceps (two origins) and triceps (three origins- figure below) Location of attachments- named according to point of origin and insertion (origin named first) •

Ex- sternocleidomastoid- attaches sternum to clavicle with insertion on mastoid process

Muscle action- named for action they produce •

Ex- flexor, extensor, and adductor

Several criteria can be combined •

Ex- extensor (extends) capri (wrist) radialis (radius), longus (length is long)

Fascicle Arrangements • •

•

All skeletal muscles consist of fascicles (bundles of fibers) Fascicle arrangements vary, resulting in muscles with different shapes and functional capabilities The most common patterns of arrangement o Circular  

o

Convergent •

•

o

Broad origin; fascicles converge toward single tendon insertion Ex- pectoralis major

Parallel • • • •

o

Fascicles arranged in concentric rings Ex- orbicularis oris

Pennate

Fascicles parallel to long axis of straplike muscle Ex- sartorius Fusiform: spindle-shaped muscles with parallel fibers Ex- biceps brachii

•

Pennate- short fascicles attach obliquely to central tendon running length of muscle o Ex- rectus femoris

•

Three forms o Unipennate: fascicles attach only to one side of tendon o Bipennate: fascicles insert from opposite sides of tendon  Rectus femoris o Multipennate: appears as feathers inserting into one tendon  deltoid  Extensor digitorum longus

Fascicle Arrangements (cont.) • Most common patterns are circular, convergent, parallel, fusiform, and pennate • Fascicles determine muscle’s range of motion o Amount of movement when muscle shortens • Fascicles determine muscle’s power o Long fibers more parallel to long axis shorten more; usually not powerful o Power depends on number of muscle fibers  Bipennate, multipennate muscles have most fibers →shorten little but are powerful...