Ch 9 Muscles Part 1 Flashcards Preview

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Flashcards in Ch 9 Muscles Part 1 Deck (23):

Muscle Tissues All contractile muscles

Skeletal, Smooth, Cardiac


Muscle action and interaction

Pull, Never push

what one group does one undoes

Skeletal muscles produce movements by exerting force on tendons. Tendons attach to and pull on bones, and movement occurs


Muscle functional group

Prime mover (agonist)- major responsibility for producing specific movement

Antagonist - Opposes or reverses particular movement

Prime mover and antagonist on opposite sides of joint across which they act


Skeletal Muscle functional group

Synergist- helps prime movers
Adds extra force to same movement
Reduces undesirable or unnecessary movement

Fixator- Synergist that immobilizes bone or muscle's origin
Gives prime mover stable base on which to act

Same muscle may be
Prime mover of one movement
Antagonist for different movement
Synergist for third movement


Origin and Insertion

Most muscles cross at least one joint and are attached at the articulating bones

When a muscle contracts, it draws one articulating bone toward the other

Origin – the attachment to the stationary bone
Insertion – the attachment to the moveable bone


Naming Skeletal Muscle

Muscle location- bone or body region with which muscle associated

Muscle shape- deltoid muscle (deltoid = triangle)

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

Direction of muscle fibers or fascicles-
rectus (fibers run straight), transversus (fibers run at right angles), and oblique (fibers run at angles)

Number of origins- Biceps (2 origins) and triceps (3 origins)

Location of attachments- named according to point of origin and insertion (origin named first)

Muscle action- named for action they produce (flexor or extensor)


Muscle Mechanic

Additional factors contributing to muscle force and speed
-Fascicle arrangement
-Lever systems

Most common patterns – circular, convergent, parallel, fusiform, pennate


Important of Fascicle arrangement

Muscle fibers are arranged in parallel bundles within fascicles but the arrangement of fasciculi in relation to the tendon can vary

Fascicular arrangement is correlated with:
The amount of power of a muscle can produce
The range of motion a muscle can produce


Arrangement of Fasicle

Determines muscle's range of motion-
Amount of movement when muscle shortens

Determines muscle's power-
Long fibers more parallel to long axis shorten more; usually not powerful

Power depends on number of muscle fibers-
Bipennate, multipennate muscles have most fibers  shorten little but powerful


Muscle Mechanic Lever System

Components of lever system
Lever—rigid bar (bone) that moves on a fixed point called fulcrum (joint)

Effort—force (supplied by muscle contraction) applied to lever to move resistance (load)

Load—resistance (bone + tissues + any added weight) moved by the effort

Bones serve as levers and joint serve as fulcrums
The lever is acted on by:


Lever: Power vs Speed

Levers allow given effort to move heavier load; move load farther or faster

Depends on fulcrum position relative to load and effort

Mechanical advantage (power lever) – load close to fulcrum; effort far from fulcrum
Small effort can move large load

Mechanical disadvantage (speed lever) – load far from fulcrum; effort close to fulcrum
Load moved rapidly over large distance; wide range of motion


Classes of Levers

Effort farther than load from fulcrum = lever operates at mechanical advantage

Effort nearer than load to fulcrum = lever operates at mechanical disadvantage


Major Skeletal Muscles of the Body

> 700 in body; grouped by function and location
Information for each muscle:

Location relative to other muscles
Origin and insertion—usually a joint between origin and insertion
Actions—insertion moves toward origin
Innervation—name of major nerve that supplies muscle


Muscles of the Head

Two groups
-Muscles of facial expression
-Muscles of mastication and tongue movement


Muscles of Facial Expression

Insert into skin
Important in nonverbal communication
All innervated by cranial nerve VII (facial nerve)


Muscles of Facial Expression: The Scalp

Epicranius (occipitofrontalis)
Bipartite muscle consisting of
Galea aponeurotica—cranial aponeurosis connecting two bellys
Frontal belly; occipital belly
Have alternate actions; pull scalp forward and backward


Muscles of Mastication

Four pairs involved in mastication;
all innervated by cranial nerve V (trigeminal nerve)

Prime movers of jaw closure
Temporalis and masseter
Grinding movements
Medial and lateral pterygoids
Chewing role - holds food between teeth


Muscles of Mastication and Tongue Movement

Three muscles anchor and move tongue
All innervated by cranial nerve XII - hypoglossal nerve


Muscles of the Anterior Neck and Throat

Two groups -
- Suprahyoid muscles
-Infrahyoid muscles

Most involved in swallowing


Suprahyoid Muscles of the Anterior Neck and Throat

Elevate the hyoid and widen the esophagus during swallowing

Digastric, geniohyoid, stylohyoid, mylohyoid


Infrahyoid Muscles of the Anterior Neck and Throat

Four deep muscles involved in swallowing (move hyoid bone and larynx)

Form floor of oral cavity
Anchor tongue
Move hyoid bone and larynx

Sternohyoid, sternothyroid, thyrohyoid, omohyoid


Muscles of the Neck and Vertebral Column

Two functional groups:
-Muscles that move head
-Muscles that extend trunk and maintain posture

Sternocleidomastoid—major head flexor

Suprahyoid and infrahyoid—synergists to head flexion
Sternocleidomastoid and scalenes—lateral head movements

Splenius capitis and cervicis portions - head extension, rotation, and lateral bending

Semispinalis capitis—synergist with sternocleidomastoid


Muscles of the Neck and Vertebral Column: Trunk Extension

Deep (intrinsic) back muscles-
Erector spinae (sacrospinalis) group—prime movers of back extension and lateral bending


Semispinalis and quadratus lumborum—synergists in extension and rotation